Merge remote-tracking branch 'upstream/master' into overlayfs-store

doc/manual/generate-builtin-constants.nix

@@ -10,12 +10,14 @@ let
       type' = optionalString (type != null) " (${type})";
 
       impureNotice = optionalString impure-only ''
-        Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
+        > **Note**
+        >
+        > Not available in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
       '';
     in
     squash ''
-      <dt id="builtin-constants-${name}">
+      <dt id="builtins-${name}">
-        <a href="#builtin-constants-${name}"><code>${name}</code>${type'}</a>
+        <a href="#builtins-${name}"><code>${name}</code></a>${type'}
       </dt>
       <dd>
 

doc/manual/src/SUMMARY.md.in

@@ -109,6 +109,7 @@
   - [C++ style guide](contributing/cxx.md)
 - [Release Notes](release-notes/release-notes.md)
   - [Release X.Y (202?-??-??)](release-notes/rl-next.md)
+  - [Release 2.17 (2023-07-24)](release-notes/rl-2.17.md)
   - [Release 2.16 (2023-05-31)](release-notes/rl-2.16.md)
   - [Release 2.15 (2023-04-11)](release-notes/rl-2.15.md)
   - [Release 2.14 (2023-02-28)](release-notes/rl-2.14.md)

doc/manual/src/contributing/hacking.md

@@ -128,7 +128,7 @@ platform. Common solutions include [remote builders] and [binary format emulatio
 (only supported on NixOS).
 
 [remote builders]: ../advanced-topics/distributed-builds.md
-[binfmt emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
+[binary format emulation]: https://nixos.org/manual/nixos/stable/options.html#opt-boot.binfmt.emulatedSystems
 
 Given such a setup, executing the build only requires selecting the respective attribute.
 For example, to compile for `aarch64-linux`:
@@ -166,7 +166,7 @@ When Nix is built such that `./configure` is passed any of the `--host`, `--buil
 <cpu>-<vendor>[-<kernel>]-<os>
 ```
 
-For historic reasons and backward-compatibility, some CPU and OS identifiers are translated from the GNU Autotools naming convention in [`configure.ac`](https://github.com/nixos/nix/blob/master/config/config.sub) as follows:
+For historic reasons and backward-compatibility, some CPU and OS identifiers are translated from the GNU Autotools naming convention in [`configure.ac`](https://github.com/nixos/nix/blob/master/configure.ac) as follows:
 
 | `config.guess`             | Nix                 |
 |----------------------------|---------------------|

doc/manual/src/release-notes/rl-2.17.md

@@ -0,0 +1,29 @@
+# Release 2.17 (2023-07-24)
+
+* [`nix-channel`](../command-ref/nix-channel.md) now supports a `--list-generations` subcommand.
+
+* The function [`builtins.fetchClosure`](../language/builtins.md#builtins-fetchClosure) can now fetch input-addressed paths in [pure evaluation mode](../command-ref/conf-file.md#conf-pure-eval), as those are not impure.
+
+* Nix now allows unprivileged/[`allowed-users`](../command-ref/conf-file.md#conf-allowed-users) to sign paths.
+  Previously, only [`trusted-users`](../command-ref/conf-file.md#conf-trusted-users) users could sign paths.
+
+* Nested dynamic attributes are now merged correctly by the parser. For example:
+
+  ```nix
+  {
+    nested = { foo = 1; };
+    nested = { ${"ba" + "r"} = 2; };
+  }
+  ```
+
+  This used to silently discard `nested.bar`, but now behaves as one would expect and evaluates to:
+
+  ```nix
+  { nested = { bar = 2; foo = 1; }; }
+  ```
+
+  Note that the feature of merging multiple attribute set declarations is of questionable value.
+  It allows writing expressions that are very hard to read, for instance when there are many lines of code between two declarations of the same attribute.
+  This has been around for a long time and is therefore supported for backwards compatibility, but should not be relied upon.
+
+* Tarball flakes can now redirect to an "immutable" URL that will be recorded in lock files. This allows the use of "mutable" tarball URLs like `https://example.org/hello/latest.tar.gz` in flakes. See the [tarball fetcher](../protocols/tarball-fetcher.md) for details.

doc/manual/src/release-notes/rl-next.md

@@ -1,8 +1 @@
 # Release X.Y (202?-??-??)
-
-- [`nix-channel`](../command-ref/nix-channel.md) now supports a `--list-generations` subcommand
-
-* The function [`builtins.fetchClosure`](../language/builtins.md#builtins-fetchClosure) can now fetch input-addressed paths in [pure evaluation mode](../command-ref/conf-file.md#conf-pure-eval), as those are not impure.
-
-- Nix now allows unprivileged/[`allowed-users`](../command-ref/conf-file.md#conf-allowed-users) to sign paths.
-  Previously, only [`trusted-users`](../command-ref/conf-file.md#conf-trusted-users) users could sign paths.

perl/lib/Nix/Store.xs

@@ -294,10 +294,8 @@ SV * makeFixedOutputPath(int recursive, char * algo, char * hash, char * name)
             auto h = Hash::parseAny(hash, parseHashType(algo));
             auto method = recursive ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat;
             auto path = store()->makeFixedOutputPath(name, FixedOutputInfo {
-                .hash = {
                 .method = method,
                 .hash = h,
-                },
                 .references = {},
             });
             XPUSHs(sv_2mortal(newSVpv(store()->printStorePath(path).c_str(), 0)));

src/libcmd/built-path.hh

@@ -1,4 +1,5 @@
 #include "derived-path.hh"
+#include "realisation.hh"
 
 namespace nix {
 

src/libexpr/eval.hh

@@ -806,7 +806,7 @@ struct EvalSettings : Config
           List of directories to be searched for `<...>` file references
 
           In particular, outside of [pure evaluation mode](#conf-pure-evaluation), this determines the value of
-          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtin-constants-nixPath).
+          [`builtins.nixPath`](@docroot@/language/builtin-constants.md#builtins-nixPath).
         )"};
 
     Setting<bool> restrictEval{

src/libexpr/parser.y

@@ -137,6 +137,7 @@ static void addAttr(ExprAttrs * attrs, AttrPath && attrPath,
                         dupAttr(state, ad.first, j2->second.pos, ad.second.pos);
                     jAttrs->attrs.emplace(ad.first, ad.second);
                 }
+                jAttrs->dynamicAttrs.insert(jAttrs->dynamicAttrs.end(), ae->dynamicAttrs.begin(), ae->dynamicAttrs.end());
             } else {
                 dupAttr(state, attrPath, pos, j->second.pos);
             }

src/libexpr/primops.cc

@@ -1300,9 +1300,10 @@ drvName, Bindings * attrs, Value & v)
         auto method = ingestionMethod.value_or(FileIngestionMethod::Flat);
 
         DerivationOutput::CAFixed dof {
-            .ca = ContentAddress::fromParts(
+            .ca = ContentAddress {
-                std::move(method),
+                .method = std::move(method),
-                std::move(h)),
+                .hash = std::move(h),
+            },
         };
 
         drv.env["out"] = state.store->printStorePath(dof.path(*state.store, drvName, "out"));
@@ -2164,10 +2165,8 @@ static void addPath(
         std::optional<StorePath> expectedStorePath;
         if (expectedHash)
             expectedStorePath = state.store->makeFixedOutputPath(name, FixedOutputInfo {
-                .hash = {
                 .method = method,
                 .hash = *expectedHash,
-                },
                 .references = {},
             });
 

src/libexpr/primops/fetchTree.cc

@@ -254,10 +254,8 @@ static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v
         auto expectedPath = state.store->makeFixedOutputPath(
             name,
             FixedOutputInfo {
-                .hash = {
                 .method = unpack ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat,
                 .hash = *expectedHash,
-                },
                 .references = {}
             });
 

src/libfetchers/fetchers.cc

@@ -217,10 +217,8 @@ StorePath Input::computeStorePath(Store & store) const
     if (!narHash)
         throw Error("cannot compute store path for unlocked input '%s'", to_string());
     return store.makeFixedOutputPath(getName(), FixedOutputInfo {
-        .hash = {
         .method = FileIngestionMethod::Recursive,
         .hash = *narHash,
-        },
         .references = {},
     });
 }

src/libfetchers/tarball.cc

@@ -77,10 +77,8 @@ DownloadFileResult downloadFile(
             *store,
             name,
             FixedOutputInfo {
-                .hash = {
                 .method = FileIngestionMethod::Flat,
                 .hash = hash,
-                },
                 .references = {},
             },
             hashString(htSHA256, sink.s),

src/libstore/binary-cache-store.cc

@@ -309,10 +309,8 @@ StorePath BinaryCacheStore::addToStoreFromDump(Source & dump, std::string_view n
             *this,
             name,
             FixedOutputInfo {
-                .hash = {
                 .method = method,
                 .hash = nar.first,
-                },
                 .references = {
                     .others = references,
                     // caller is not capable of creating a self-reference, because this is content-addressed without modulus
@@ -428,10 +426,8 @@ StorePath BinaryCacheStore::addToStore(
             *this,
             name,
             FixedOutputInfo {
-                .hash = {
                 .method = method,
                 .hash = h,
-                },
                 .references = {
                     .others = references,
                     // caller is not capable of creating a self-reference, because this is content-addressed without modulus
@@ -465,8 +461,8 @@ StorePath BinaryCacheStore::addTextToStore(
             *this,
             std::string { name },
             TextInfo {
-                { .hash = textHash },
+                .hash = textHash,
-                references,
+                .references = references,
             },
             nar.first,
         };

src/libstore/build/local-derivation-goal.cc

@@ -1,5 +1,5 @@
 #include "local-derivation-goal.hh"
-#include "gc-store.hh"
+#include "indirect-root-store.hh"
 #include "hook-instance.hh"
 #include "worker.hh"
 #include "builtins.hh"
@@ -1200,7 +1200,7 @@ struct RestrictedStoreConfig : virtual LocalFSStoreConfig
 /* A wrapper around LocalStore that only allows building/querying of
    paths that are in the input closures of the build or were added via
    recursive Nix calls. */
-struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual LocalFSStore, public virtual GcStore
+struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual IndirectRootStore, public virtual GcStore
 {
     ref<LocalStore> next;
 
@@ -1251,11 +1251,13 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
     void queryReferrers(const StorePath & path, StorePathSet & referrers) override
     { }
 
-    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path) override
+    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(
+        const StorePath & path,
+        Store * evalStore = nullptr) override
     {
         if (!goal.isAllowed(path))
             throw InvalidPath("cannot query output map for unknown path '%s' in recursive Nix", printStorePath(path));
-        return next->queryPartialDerivationOutputMap(path);
+        return next->queryPartialDerivationOutputMap(path, evalStore);
     }
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
@@ -2540,16 +2542,16 @@ SingleDrvOutputs LocalDerivationGoal::registerOutputs()
             },
 
             [&](const DerivationOutput::CAFixed & dof) {
-                auto wanted = dof.ca.getHash();
+                auto & wanted = dof.ca.hash;
 
                 auto newInfo0 = newInfoFromCA(DerivationOutput::CAFloating {
-                    .method = dof.ca.getMethod(),
+                    .method = dof.ca.method,
                     .hashType = wanted.type,
                 });
 
                 /* Check wanted hash */
                 assert(newInfo0.ca);
-                auto got = newInfo0.ca->getHash();
+                auto & got = newInfo0.ca->hash;
                 if (wanted != got) {
                     /* Throw an error after registering the path as
                        valid. */

src/libstore/content-address.cc

@@ -4,11 +4,6 @@
 
 namespace nix {
 
-std::string FixedOutputHash::printMethodAlgo() const
-{
-    return makeFileIngestionPrefix(method) + printHashType(hash.type);
-}
-
 std::string makeFileIngestionPrefix(FileIngestionMethod m)
 {
     switch (m) {
@@ -42,21 +37,6 @@ ContentAddressMethod ContentAddressMethod::parsePrefix(std::string_view & m)
     return method;
 }
 
-std::string ContentAddress::render() const
-{
-    return std::visit(overloaded {
-        [](const TextHash & th) {
-            return "text:"
-                + th.hash.to_string(Base32, true);
-        },
-        [](const FixedOutputHash & fsh) {
-            return "fixed:"
-                + makeFileIngestionPrefix(fsh.method)
-                + fsh.hash.to_string(Base32, true);
-        }
-    }, raw);
-}
-
 std::string ContentAddressMethod::render(HashType ht) const
 {
     return std::visit(overloaded {
@@ -69,6 +49,20 @@ std::string ContentAddressMethod::render(HashType ht) const
     }, raw);
 }
 
+std::string ContentAddress::render() const
+{
+    return std::visit(overloaded {
+        [](const TextIngestionMethod &) -> std::string {
+            return "text:";
+        },
+        [](const FileIngestionMethod & method) {
+            return "fixed:"
+                + makeFileIngestionPrefix(method);
+        },
+    }, method.raw)
+        + this->hash.to_string(Base32, true);
+}
+
 /**
  * Parses content address strings up to the hash.
  */
@@ -118,22 +112,12 @@ ContentAddress ContentAddress::parse(std::string_view rawCa)
 {
     auto rest = rawCa;
 
-    auto [caMethod, hashType_] = parseContentAddressMethodPrefix(rest);
+    auto [caMethod, hashType] = parseContentAddressMethodPrefix(rest);
-    auto hashType = hashType_; // work around clang bug
 
-    return std::visit(overloaded {
+    return ContentAddress {
-        [&](TextIngestionMethod &) {
+        .method = std::move(caMethod).raw,
-            return ContentAddress(TextHash {
-                .hash = Hash::parseNonSRIUnprefixed(rest, hashType)
-            });
-        },
-        [&](FileIngestionMethod & fim) {
-            return ContentAddress(FixedOutputHash {
-                .method = fim,
         .hash = Hash::parseNonSRIUnprefixed(rest, hashType),
-            });
+    };
-        },
-    }, caMethod.raw);
 }
 
 std::pair<ContentAddressMethod, HashType> ContentAddressMethod::parse(std::string_view caMethod)
@@ -156,52 +140,10 @@ std::string renderContentAddress(std::optional<ContentAddress> ca)
     return ca ? ca->render() : "";
 }
 
-ContentAddress ContentAddress::fromParts(
-    ContentAddressMethod method, Hash hash) noexcept
-{
-    return std::visit(overloaded {
-        [&](TextIngestionMethod _) -> ContentAddress {
-            return TextHash {
-                .hash = std::move(hash),
-            };
-        },
-        [&](FileIngestionMethod m2) -> ContentAddress {
-            return FixedOutputHash {
-                .method = std::move(m2),
-                .hash = std::move(hash),
-            };
-        },
-    }, method.raw);
-}
-
-ContentAddressMethod ContentAddress::getMethod() const
-{
-    return std::visit(overloaded {
-        [](const TextHash & th) -> ContentAddressMethod {
-            return TextIngestionMethod {};
-        },
-        [](const FixedOutputHash & fsh) -> ContentAddressMethod {
-            return fsh.method;
-        },
-    }, raw);
-}
-
-const Hash & ContentAddress::getHash() const
-{
-    return std::visit(overloaded {
-        [](const TextHash & th) -> auto & {
-            return th.hash;
-        },
-        [](const FixedOutputHash & fsh) -> auto & {
-            return fsh.hash;
-        },
-    }, raw);
-}
-
 std::string ContentAddress::printMethodAlgo() const
 {
-    return getMethod().renderPrefix()
+    return method.renderPrefix()
-        + printHashType(getHash().type);
+        + printHashType(hash.type);
 }
 
 bool StoreReferences::empty() const
@@ -217,19 +159,20 @@ size_t StoreReferences::size() const
 ContentAddressWithReferences ContentAddressWithReferences::withoutRefs(const ContentAddress & ca) noexcept
 {
     return std::visit(overloaded {
-        [&](const TextHash & h) -> ContentAddressWithReferences {
+        [&](const TextIngestionMethod &) -> ContentAddressWithReferences {
             return TextInfo {
-                .hash = h,
+                .hash = ca.hash,
                 .references = {},
             };
         },
-        [&](const FixedOutputHash & h) -> ContentAddressWithReferences {
+        [&](const FileIngestionMethod & method) -> ContentAddressWithReferences {
             return FixedOutputInfo {
-                .hash = h,
+                .method = method,
+                .hash = ca.hash,
                 .references = {},
             };
         },
-    }, ca.raw);
+    }, ca.method.raw);
 }
 
 std::optional<ContentAddressWithReferences> ContentAddressWithReferences::fromPartsOpt(
@@ -241,7 +184,7 @@ std::optional<ContentAddressWithReferences> ContentAddressWithReferences::fromPa
                 return std::nullopt;
             return ContentAddressWithReferences {
                 TextInfo {
-                    .hash = { .hash = std::move(hash) },
+                    .hash = std::move(hash),
                     .references = std::move(refs.others),
                 }
             };
@@ -249,10 +192,8 @@ std::optional<ContentAddressWithReferences> ContentAddressWithReferences::fromPa
         [&](FileIngestionMethod m2) -> std::optional<ContentAddressWithReferences> {
             return ContentAddressWithReferences {
                 FixedOutputInfo {
-                    .hash = {
                     .method = m2,
                     .hash = std::move(hash),
-                    },
                     .references = std::move(refs),
                 }
             };
@@ -267,7 +208,7 @@ ContentAddressMethod ContentAddressWithReferences::getMethod() const
             return TextIngestionMethod {};
         },
         [](const FixedOutputInfo & fsh) -> ContentAddressMethod {
-            return fsh.hash.method;
+            return fsh.method;
         },
     }, raw);
 }
@@ -276,10 +217,10 @@ Hash ContentAddressWithReferences::getHash() const
 {
     return std::visit(overloaded {
         [](const TextInfo & th) {
-            return th.hash.hash;
+            return th.hash;
         },
         [](const FixedOutputInfo & fsh) {
-            return fsh.hash.hash;
+            return fsh.hash;
         },
     }, raw);
 }

src/libstore/content-address.hh

@@ -113,37 +113,6 @@ struct ContentAddressMethod
  * Mini content address
  */
 
-/**
- * Somewhat obscure, used by \ref Derivation derivations and
- * `builtins.toFile` currently.
- */
-struct TextHash {
-    /**
-     * Hash of the contents of the text/file.
-     */
-    Hash hash;
-
-    GENERATE_CMP(TextHash, me->hash);
-};
-
-/**
- * Used by most store objects that are content-addressed.
- */
-struct FixedOutputHash {
-    /**
-     * How the file system objects are serialized
-     */
-    FileIngestionMethod method;
-    /**
-     * Hash of that serialization
-     */
-    Hash hash;
-
-    std::string printMethodAlgo() const;
-
-    GENERATE_CMP(FixedOutputHash, me->method, me->hash);
-};
-
 /**
  * We've accumulated several types of content-addressed paths over the
  * years; fixed-output derivations support multiple hash algorithms and
@@ -158,19 +127,17 @@ struct FixedOutputHash {
  */
 struct ContentAddress
 {
-    typedef std::variant<
+    /**
-        TextHash,
+     * How the file system objects are serialized
-        FixedOutputHash
+     */
-    > Raw;
+    ContentAddressMethod method;
 
-    Raw raw;
+    /**
+     * Hash of that serialization
+     */
+    Hash hash;
 
-    GENERATE_CMP(ContentAddress, me->raw);
+    GENERATE_CMP(ContentAddress, me->method, me->hash);
-
-    /* The moral equivalent of `using Raw::Raw;` */
-    ContentAddress(auto &&... arg)
-        : raw(std::forward<decltype(arg)>(arg)...)
-    { }
 
     /**
      * Compute the content-addressability assertion
@@ -183,20 +150,6 @@ struct ContentAddress
 
     static std::optional<ContentAddress> parseOpt(std::string_view rawCaOpt);
 
-    /**
-     * Create a `ContentAddress` from 2 parts:
-     *
-     * @param method Way ingesting the file system data.
-     *
-     * @param hash Hash of ingested file system data.
-     */
-    static ContentAddress fromParts(
-        ContentAddressMethod method, Hash hash) noexcept;
-
-    ContentAddressMethod getMethod() const;
-
-    const Hash & getHash() const;
-
     std::string printMethodAlgo() const;
 };
 
@@ -219,7 +172,8 @@ std::string renderContentAddress(std::optional<ContentAddress> ca);
  * References to other store objects are tracked with store paths, self
  * references however are tracked with a boolean.
  */
-struct StoreReferences {
+struct StoreReferences
+{
     /**
      * References to other store objects
      */
@@ -246,8 +200,13 @@ struct StoreReferences {
 };
 
 // This matches the additional info that we need for makeTextPath
-struct TextInfo {
+struct TextInfo
-    TextHash hash;
+{
+    /**
+     * Hash of the contents of the text/file.
+     */
+    Hash hash;
+
     /**
      * References to other store objects only; self references
      * disallowed
@@ -257,8 +216,18 @@ struct TextInfo {
     GENERATE_CMP(TextInfo, me->hash, me->references);
 };
 
-struct FixedOutputInfo {
+struct FixedOutputInfo
-    FixedOutputHash hash;
+{
+    /**
+     * How the file system objects are serialized
+     */
+    FileIngestionMethod method;
+
+    /**
+     * Hash of that serialization
+     */
+    Hash hash;
+
     /**
      * References to other store objects or this one.
      */

src/libstore/daemon.cc

@@ -7,6 +7,7 @@
 #include "store-cast.hh"
 #include "gc-store.hh"
 #include "log-store.hh"
+#include "indirect-root-store.hh"
 #include "path-with-outputs.hh"
 #include "finally.hh"
 #include "archive.hh"
@@ -675,8 +676,8 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
         Path path = absPath(readString(from));
 
         logger->startWork();
-        auto & gcStore = require<GcStore>(*store);
+        auto & indirectRootStore = require<IndirectRootStore>(*store);
-        gcStore.addIndirectRoot(path);
+        indirectRootStore.addIndirectRoot(path);
         logger->stopWork();
 
         to << 1;

src/libstore/derivations.cc

@@ -232,9 +232,10 @@ static DerivationOutput parseDerivationOutput(const Store & store,
             validatePath(pathS);
             auto hash = Hash::parseNonSRIUnprefixed(hashS, hashType);
             return DerivationOutput::CAFixed {
-                .ca = ContentAddress::fromParts(
+                .ca = ContentAddress {
-                    std::move(method),
+                    .method = std::move(method),
-                    std::move(hash)),
+                    .hash = std::move(hash),
+                },
             };
         } else {
             experimentalFeatureSettings.require(Xp::CaDerivations);
@@ -395,7 +396,7 @@ std::string Derivation::unparse(const Store & store, bool maskOutputs,
             [&](const DerivationOutput::CAFixed & dof) {
                 s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(dof.path(store, name, i.first)));
                 s += ','; printUnquotedString(s, dof.ca.printMethodAlgo());
-                s += ','; printUnquotedString(s, dof.ca.getHash().to_string(Base16, false));
+                s += ','; printUnquotedString(s, dof.ca.hash.to_string(Base16, false));
             },
             [&](const DerivationOutput::CAFloating & dof) {
                 s += ','; printUnquotedString(s, "");
@@ -628,7 +629,7 @@ DrvHash hashDerivationModulo(Store & store, const Derivation & drv, bool maskOut
             auto & dof = std::get<DerivationOutput::CAFixed>(i.second.raw());
             auto hash = hashString(htSHA256, "fixed:out:"
                 + dof.ca.printMethodAlgo() + ":"
-                + dof.ca.getHash().to_string(Base16, false) + ":"
+                + dof.ca.hash.to_string(Base16, false) + ":"
                 + store.printStorePath(dof.path(store, drv.name, i.first)));
             outputHashes.insert_or_assign(i.first, std::move(hash));
         }
@@ -780,7 +781,7 @@ void writeDerivation(Sink & out, const Store & store, const BasicDerivation & dr
             [&](const DerivationOutput::CAFixed & dof) {
                 out << store.printStorePath(dof.path(store, drv.name, i.first))
                     << dof.ca.printMethodAlgo()
-                    << dof.ca.getHash().to_string(Base16, false);
+                    << dof.ca.hash.to_string(Base16, false);
             },
             [&](const DerivationOutput::CAFloating & dof) {
                 out << ""
@@ -970,7 +971,7 @@ nlohmann::json DerivationOutput::toJSON(
         [&](const DerivationOutput::CAFixed & dof) {
             res["path"] = store.printStorePath(dof.path(store, drvName, outputName));
             res["hashAlgo"] = dof.ca.printMethodAlgo();
-            res["hash"] = dof.ca.getHash().to_string(Base16, false);
+            res["hash"] = dof.ca.hash.to_string(Base16, false);
             // FIXME print refs?
         },
         [&](const DerivationOutput::CAFloating & dof) {
@@ -1017,9 +1018,10 @@ DerivationOutput DerivationOutput::fromJSON(
     else if (keys == (std::set<std::string_view> { "path", "hashAlgo", "hash" })) {
         auto [method, hashType] = methodAlgo();
         auto dof = DerivationOutput::CAFixed {
-            .ca = ContentAddress::fromParts(
+            .ca = ContentAddress {
-                std::move(method),
+                .method = std::move(method),
-                Hash::parseNonSRIUnprefixed((std::string) json["hash"], hashType)),
+                .hash = Hash::parseNonSRIUnprefixed((std::string) json["hash"], hashType),
+            },
         };
         if (dof.path(store, drvName, outputName) != store.parseStorePath((std::string) json["path"]))
             throw Error("Path doesn't match derivation output");

src/libstore/derived-path.hh

@@ -3,7 +3,6 @@
 
 #include "util.hh"
 #include "path.hh"
-#include "realisation.hh"
 #include "outputs-spec.hh"
 #include "comparator.hh"
 

src/libstore/gc-store.hh

@@ -71,19 +71,36 @@ struct GCResults
 };
 
 
+/**
+ * Mix-in class for \ref Store "stores" which expose a notion of garbage
+ * collection.
+ *
+ * Garbage collection will allow deleting paths which are not
+ * transitively "rooted".
+ *
+ * The notion of GC roots actually not part of this class.
+ *
+ *  - The base `Store` class has `Store::addTempRoot()` because for a store
+ *    that doesn't support garbage collection at all, a temporary GC root is
+ *    safely implementable as no-op.
+ *
+ *    @todo actually this is not so good because stores are *views*.
+ *    Some views have only a no-op temp roots even though others to the
+ *    same store allow triggering GC. For instance one can't add a root
+ *    over ssh, but that doesn't prevent someone from gc-ing that store
+ *    accesed via SSH locally).
+ *
+ *  - The derived `LocalFSStore` class has `LocalFSStore::addPermRoot`,
+ *    which is not part of this class because it relies on the notion of
+ *    an ambient file system. There are stores (`ssh-ng://`, for one),
+ *    that *do* support garbage collection but *don't* expose any file
+ *    system, and `LocalFSStore::addPermRoot` thus does not make sense
+ *    for them.
+ */
 struct GcStore : public virtual Store
 {
     inline static std::string operationName = "Garbage collection";
 
-    /**
-     * Add an indirect root, which is merely a symlink to `path` from
-     * `/nix/var/nix/gcroots/auto/<hash of path>`.  `path` is supposed
-     * to be a symlink to a store path.  The garbage collector will
-     * automatically remove the indirect root when it finds that
-     * `path` has disappeared.
-     */
-    virtual void addIndirectRoot(const Path & path) = 0;
-
     /**
      * Find the roots of the garbage collector.  Each root is a pair
      * `(link, storepath)` where `link` is the path of the symlink

src/libstore/gc.cc

@@ -1,7 +1,6 @@
 #include "derivations.hh"
 #include "globals.hh"
 #include "local-store.hh"
-#include "local-fs-store.hh"
 #include "finally.hh"
 
 #include <functional>
@@ -50,7 +49,7 @@ void LocalStore::addIndirectRoot(const Path & path)
 }
 
 
-Path LocalFSStore::addPermRoot(const StorePath & storePath, const Path & _gcRoot)
+Path IndirectRootStore::addPermRoot(const StorePath & storePath, const Path & _gcRoot)
 {
     Path gcRoot(canonPath(_gcRoot));
 

src/libstore/indirect-root-store.hh

@@ -0,0 +1,48 @@
+#pragma once
+///@file
+
+#include "local-fs-store.hh"
+
+namespace nix {
+
+/**
+ * Mix-in class for implementing permanent roots as a pair of a direct
+ * (strong) reference and indirect weak reference to the first
+ * reference.
+ *
+ * See methods for details on the operations it represents.
+ */
+struct IndirectRootStore : public virtual LocalFSStore
+{
+    inline static std::string operationName = "Indirect GC roots registration";
+
+    /**
+     * Implementation of `LocalFSStore::addPermRoot` where the permanent
+     * root is a pair of
+     *
+     * - The user-facing symlink which all implementations must create
+     *
+     * - An additional weak reference known as the "indirect root" that
+     *   points to that symlink.
+     *
+     * The garbage collector will automatically remove the indirect root
+     * when it finds that the symlink has disappeared.
+     *
+     * The implementation of this method is concrete, but it delegates
+     * to `addIndirectRoot()` which is abstract.
+     */
+    Path addPermRoot(const StorePath & storePath, const Path & gcRoot) override final;
+
+    /**
+     * Add an indirect root, which is a weak reference to the
+     * user-facing symlink created by `addPermRoot()`.
+     *
+     * @param path user-facing and user-controlled symlink to a store
+     * path.
+     *
+     * The form this weak-reference takes is implementation-specific.
+     */
+    virtual void addIndirectRoot(const Path & path) = 0;
+};
+
+}

src/libstore/local-fs-store.hh

@@ -40,6 +40,7 @@ class LocalFSStore : public virtual LocalFSStoreConfig,
     public virtual LogStore
 {
 public:
+    inline static std::string operationName = "Local Filesystem Store";
 
     const static std::string drvsLogDir;
 
@@ -49,9 +50,20 @@ public:
     ref<FSAccessor> getFSAccessor() override;
 
     /**
-     * Register a permanent GC root.
+     * Creates symlink from the `gcRoot` to the `storePath` and
+     * registers the `gcRoot` as a permanent GC root. The `gcRoot`
+     * symlink lives outside the store and is created and owned by the
+     * user.
+     *
+     * @param gcRoot The location of the symlink.
+     *
+     * @param storePath The store object being rooted. The symlink will
+     * point to `toRealPath(store.printStorePath(storePath))`.
+     *
+     * How the permanent GC root corresponding to this symlink is
+     * managed is implementation-specific.
      */
-    Path addPermRoot(const StorePath & storePath, const Path & gcRoot);
+    virtual Path addPermRoot(const StorePath & storePath, const Path & gcRoot) = 0;
 
     virtual Path getRealStoreDir() { return realStoreDir; }
 

src/libstore/local-store.cc

@@ -1028,10 +1028,9 @@ StorePathSet LocalStore::queryValidDerivers(const StorePath & path)
 
 
 std::map<std::string, std::optional<StorePath>>
-LocalStore::queryPartialDerivationOutputMap(const StorePath & path_)
+LocalStore::queryStaticPartialDerivationOutputMap(const StorePath & path)
 {
-    auto path = path_;
+    return retrySQLite<std::map<std::string, std::optional<StorePath>>>([&]() {
-    auto outputs = retrySQLite<std::map<std::string, std::optional<StorePath>>>([&]() {
         auto state(_state.lock());
         std::map<std::string, std::optional<StorePath>> outputs;
         uint64_t drvId;
@@ -1043,21 +1042,6 @@ LocalStore::queryPartialDerivationOutputMap(const StorePath & path_)
 
         return outputs;
     });
-
-    if (!experimentalFeatureSettings.isEnabled(Xp::CaDerivations))
-        return outputs;
-
-    auto drv = readInvalidDerivation(path);
-    auto drvHashes = staticOutputHashes(*this, drv);
-    for (auto& [outputName, hash] : drvHashes) {
-        auto realisation = queryRealisation(DrvOutput{hash, outputName});
-        if (realisation)
-            outputs.insert_or_assign(outputName, realisation->outPath);
-        else
-            outputs.insert({outputName, std::nullopt});
-    }
-
-    return outputs;
 }
 
 std::optional<StorePath> LocalStore::queryPathFromHashPart(const std::string & hashPart)
@@ -1255,27 +1239,17 @@ void LocalStore::addToStore(const ValidPathInfo & info, Source & source,
                     printStorePath(info.path), info.narSize, hashResult.second);
 
             if (info.ca) {
-                if (auto foHash = std::get_if<FixedOutputHash>(&info.ca->raw)) {
+                auto & specified = *info.ca;
-                    auto actualFoHash = hashCAPath(
+                auto actualHash = hashCAPath(
-                        foHash->method,
+                    specified.method,
-                        foHash->hash.type,
+                    specified.hash.type,
                     info.path
                 );
-                    if (foHash->hash != actualFoHash.hash) {
+                if (specified.hash != actualHash.hash) {
                     throw Error("ca hash mismatch importing path '%s';\n  specified: %s\n  got:       %s",
                         printStorePath(info.path),
-                            foHash->hash.to_string(Base32, true),
+                        specified.hash.to_string(Base32, true),
-                            actualFoHash.hash.to_string(Base32, true));
+                        actualHash.hash.to_string(Base32, true));
-                    }
-                }
-                if (auto textHash = std::get_if<TextHash>(&info.ca->raw)) {
-                    auto actualTextHash = hashString(htSHA256, readFile(realPath));
-                    if (textHash->hash != actualTextHash) {
-                        throw Error("ca hash mismatch importing path '%s';\n  specified: %s\n  got:       %s",
-                            printStorePath(info.path),
-                            textHash->hash.to_string(Base32, true),
-                            actualTextHash.to_string(Base32, true));
-                    }
                 }
             }
 
@@ -1355,10 +1329,8 @@ StorePath LocalStore::addToStoreFromDump(Source & source0, std::string_view name
     auto [hash, size] = hashSink->finish();
 
     ContentAddressWithReferences desc = FixedOutputInfo {
-        .hash = {
         .method = method,
         .hash = hash,
-        },
         .references = {
             .others = references,
             // caller is not capable of creating a self-reference, because this is content-addressed without modulus
@@ -1434,8 +1406,8 @@ StorePath LocalStore::addTextToStore(
 {
     auto hash = hashString(htSHA256, s);
     auto dstPath = makeTextPath(name, TextInfo {
-        { .hash = hash },
+        .hash = hash,
-        references,
+        .references = references,
     });
 
     addTempRoot(dstPath);
@@ -1465,7 +1437,10 @@ StorePath LocalStore::addTextToStore(
             ValidPathInfo info { dstPath, narHash };
             info.narSize = sink.s.size();
             info.references = references;
-            info.ca = TextHash { .hash = hash };
+            info.ca = {
+                .method = TextIngestionMethod {},
+                .hash = hash,
+            };
             registerValidPath(info);
         }
 
@@ -1862,22 +1837,27 @@ void LocalStore::queryRealisationUncached(const DrvOutput & id,
     }
 }
 
-FixedOutputHash LocalStore::hashCAPath(
+ContentAddress LocalStore::hashCAPath(
-    const FileIngestionMethod & method, const HashType & hashType,
+    const ContentAddressMethod & method, const HashType & hashType,
     const StorePath & path)
 {
     return hashCAPath(method, hashType, Store::toRealPath(path), path.hashPart());
 }
 
-FixedOutputHash LocalStore::hashCAPath(
+ContentAddress LocalStore::hashCAPath(
-    const FileIngestionMethod & method,
+    const ContentAddressMethod & method,
     const HashType & hashType,
     const Path & path,
     const std::string_view pathHash
 )
 {
     HashModuloSink caSink ( hashType, std::string(pathHash) );
-    switch (method) {
+    std::visit(overloaded {
+        [&](const TextIngestionMethod &) {
+            readFile(path, caSink);
+        },
+        [&](const FileIngestionMethod & m2) {
+            switch (m2) {
             case FileIngestionMethod::Recursive:
                 dumpPath(path, caSink);
                 break;
@@ -1885,10 +1865,11 @@ FixedOutputHash LocalStore::hashCAPath(
                 readFile(path, caSink);
                 break;
             }
-    auto hash = caSink.finish().first;
+        },
-    return FixedOutputHash{
+    }, method.raw);
+    return ContentAddress {
         .method = method,
-        .hash = hash,
+        .hash = caSink.finish().first,
     };
 }
 

src/libstore/local-store.hh

@@ -5,8 +5,7 @@
 
 #include "pathlocks.hh"
 #include "store-api.hh"
-#include "local-fs-store.hh"
+#include "indirect-root-store.hh"
-#include "gc-store.hh"
 #include "sync.hh"
 #include "util.hh"
 
@@ -68,7 +67,9 @@ struct LocalStoreConfig : virtual LocalFSStoreConfig
     std::string doc() override;
 };
 
-class LocalStore : public virtual LocalStoreConfig, public virtual LocalFSStore, public virtual GcStore
+class LocalStore : public virtual LocalStoreConfig
+    , public virtual IndirectRootStore
+    , public virtual GcStore
 {
 private:
 
@@ -165,7 +166,7 @@ public:
 
     StorePathSet queryValidDerivers(const StorePath & path) override;
 
-    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path) override;
+    std::map<std::string, std::optional<StorePath>> queryStaticPartialDerivationOutputMap(const StorePath & path) override;
 
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 
@@ -209,6 +210,12 @@ private:
 
 public:
 
+    /**
+     * Implementation of IndirectRootStore::addIndirectRoot().
+     *
+     * The weak reference merely is a symlink to `path' from
+     * /nix/var/nix/gcroots/auto/<hash of `path'>.
+     */
     void addIndirectRoot(const Path & path) override;
 
 private:
@@ -352,13 +359,13 @@ private:
     void signRealisation(Realisation &);
 
     // XXX: Make a generic `Store` method
-    FixedOutputHash hashCAPath(
+    ContentAddress hashCAPath(
-        const FileIngestionMethod & method,
+        const ContentAddressMethod & method,
         const HashType & hashType,
         const StorePath & path);
 
-    FixedOutputHash hashCAPath(
+    ContentAddress hashCAPath(
-        const FileIngestionMethod & method,
+        const ContentAddressMethod & method,
         const HashType & hashType,
         const Path & path,
         const std::string_view pathHash

src/libstore/make-content-addressed.cc

@@ -52,10 +52,8 @@ std::map<StorePath, StorePath> makeContentAddressed(
             dstStore,
             path.name(),
             FixedOutputInfo {
-                .hash = {
                 .method = FileIngestionMethod::Recursive,
                 .hash = narModuloHash,
-                },
                 .references = std::move(refs),
             },
             Hash::dummy,

src/libstore/misc.cc

@@ -310,43 +310,34 @@ std::map<DrvOutput, StorePath> drvOutputReferences(
 
 OutputPathMap resolveDerivedPath(Store & store, const DerivedPath::Built & bfd, Store * evalStore_)
 {
-    auto & evalStore = evalStore_ ? *evalStore_ : store;
+    auto outputsOpt_ = store.queryPartialDerivationOutputMap(bfd.drvPath, evalStore_);
 
-    OutputPathMap outputs;
+    auto outputsOpt = std::visit(overloaded {
-    auto drv = evalStore.readDerivation(bfd.drvPath);
-    auto outputHashes = staticOutputHashes(store, drv);
-    auto drvOutputs = drv.outputsAndOptPaths(store);
-    auto outputNames = std::visit(overloaded {
         [&](const OutputsSpec::All &) {
-            StringSet names;
+            // Keep all outputs
-            for (auto & [outputName, _] : drv.outputs)
+            return std::move(outputsOpt_);
-                names.insert(outputName);
-            return names;
         },
         [&](const OutputsSpec::Names & names) {
-            return static_cast<std::set<std::string>>(names);
+            // Get just those mentioned by name
-        },
+            std::map<std::string, std::optional<StorePath>> outputsOpt;
-    }, bfd.outputs.raw());
+            for (auto & output : names) {
-    for (auto & output : outputNames) {
+                auto * pOutputPathOpt = get(outputsOpt_, output);
-        auto outputHash = get(outputHashes, output);
+                if (!pOutputPathOpt)
-        if (!outputHash)
                     throw Error(
                         "the derivation '%s' doesn't have an output named '%s'",
                         store.printStorePath(bfd.drvPath), output);
-        if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations)) {
+                outputsOpt.insert_or_assign(output, std::move(*pOutputPathOpt));
-            DrvOutput outputId { *outputHash, output };
-            auto realisation = store.queryRealisation(outputId);
-            if (!realisation)
-                throw MissingRealisation(outputId);
-            outputs.insert_or_assign(output, realisation->outPath);
-        } else {
-            // If ca-derivations isn't enabled, assume that
-            // the output path is statically known.
-            auto drvOutput = get(drvOutputs, output);
-            assert(drvOutput);
-            assert(drvOutput->second);
-            outputs.insert_or_assign(output, *drvOutput->second);
             }
+            return outputsOpt;
+        },
+    }, bfd.outputs.raw());
+
+    OutputPathMap outputs;
+    for (auto & [outputName, outputPathOpt] : outputsOpt) {
+        if (!outputPathOpt)
+            throw MissingRealisation(store.printStorePath(bfd.drvPath), outputName);
+        auto & outputPath = *outputPathOpt;
+        outputs.insert_or_assign(outputName, outputPath);
     }
     return outputs;
 }

src/libstore/path-info.cc

@@ -29,14 +29,14 @@ std::optional<ContentAddressWithReferences> ValidPathInfo::contentAddressWithRef
         return std::nullopt;
 
     return std::visit(overloaded {
-        [&](const TextHash & th) -> ContentAddressWithReferences {
+        [&](const TextIngestionMethod &) -> ContentAddressWithReferences {
             assert(references.count(path) == 0);
             return TextInfo {
-                .hash = th,
+                .hash = ca->hash,
                 .references = references,
             };
         },
-        [&](const FixedOutputHash & foh) -> ContentAddressWithReferences {
+        [&](const FileIngestionMethod & m2) -> ContentAddressWithReferences {
             auto refs = references;
             bool hasSelfReference = false;
             if (refs.count(path)) {
@@ -44,14 +44,15 @@ std::optional<ContentAddressWithReferences> ValidPathInfo::contentAddressWithRef
                 refs.erase(path);
             }
             return FixedOutputInfo {
-                .hash = foh,
+                .method = m2,
+                .hash = ca->hash,
                 .references = {
                     .others = std::move(refs),
                     .self = hasSelfReference,
                 },
             };
         },
-    }, ca->raw);
+    }, ca->method.raw);
 }
 
 bool ValidPathInfo::isContentAddressed(const Store & store) const
@@ -110,13 +111,19 @@ ValidPathInfo::ValidPathInfo(
     std::visit(overloaded {
         [this](TextInfo && ti) {
             this->references = std::move(ti.references);
-            this->ca = std::move((TextHash &&) ti);
+            this->ca = ContentAddress {
+                .method = TextIngestionMethod {},
+                .hash = std::move(ti.hash),
+            };
         },
         [this](FixedOutputInfo && foi) {
             this->references = std::move(foi.references.others);
             if (foi.references.self)
                 this->references.insert(path);
-            this->ca = std::move((FixedOutputHash &&) foi);
+            this->ca = ContentAddress {
+                .method = std::move(foi.method),
+                .hash = std::move(foi.hash),
+            };
         },
     }, std::move(ca).raw);
 }

src/libstore/realisation.hh

@@ -5,6 +5,7 @@
 
 #include "hash.hh"
 #include "path.hh"
+#include "derived-path.hh"
 #include <nlohmann/json_fwd.hpp>
 #include "comparator.hh"
 #include "crypto.hh"
@@ -143,9 +144,13 @@ class MissingRealisation : public Error
 {
 public:
     MissingRealisation(DrvOutput & outputId)
-        : Error( "cannot operate on an output of the "
+        : MissingRealisation(outputId.outputName, outputId.strHash())
+    {}
+    MissingRealisation(std::string_view drv, std::string outputName)
+        : Error( "cannot operate on output '%s' of the "
                 "unbuilt derivation '%s'",
-                outputId.to_string())
+                outputName,
+                drv)
     {}
 };
 

src/libstore/remote-store-connection.hh

@@ -1,5 +1,6 @@
 #include "remote-store.hh"
 #include "worker-protocol.hh"
+#include "pool.hh"
 
 namespace nix {
 
@@ -94,4 +95,34 @@ struct RemoteStore::Connection
     std::exception_ptr processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
 };
 
+/**
+ * A wrapper around Pool<RemoteStore::Connection>::Handle that marks
+ * the connection as bad (causing it to be closed) if a non-daemon
+ * exception is thrown before the handle is closed. Such an exception
+ * causes a deviation from the expected protocol and therefore a
+ * desynchronization between the client and daemon.
+ */
+struct RemoteStore::ConnectionHandle
+{
+    Pool<RemoteStore::Connection>::Handle handle;
+    bool daemonException = false;
+
+    ConnectionHandle(Pool<RemoteStore::Connection>::Handle && handle)
+        : handle(std::move(handle))
+    { }
+
+    ConnectionHandle(ConnectionHandle && h)
+        : handle(std::move(h.handle))
+    { }
+
+    ~ConnectionHandle();
+
+    RemoteStore::Connection & operator * () { return *handle; }
+    RemoteStore::Connection * operator -> () { return &*handle; }
+
+    void processStderr(Sink * sink = 0, Source * source = 0, bool flush = true);
+
+    void withFramedSink(std::function<void(Sink & sink)> fun);
+};
+
 }

src/libstore/remote-store.cc

@@ -159,49 +159,25 @@ void RemoteStore::setOptions(Connection & conn)
 }
 
 
-/* A wrapper around Pool<RemoteStore::Connection>::Handle that marks
+RemoteStore::ConnectionHandle::~ConnectionHandle()
-   the connection as bad (causing it to be closed) if a non-daemon
-   exception is thrown before the handle is closed. Such an exception
-   causes a deviation from the expected protocol and therefore a
-   desynchronization between the client and daemon. */
-struct ConnectionHandle
 {
-    Pool<RemoteStore::Connection>::Handle handle;
-    bool daemonException = false;
-
-    ConnectionHandle(Pool<RemoteStore::Connection>::Handle && handle)
-        : handle(std::move(handle))
-    { }
-
-    ConnectionHandle(ConnectionHandle && h)
-        : handle(std::move(h.handle))
-    { }
-
-    ~ConnectionHandle()
-    {
     if (!daemonException && std::uncaught_exceptions()) {
         handle.markBad();
         debug("closing daemon connection because of an exception");
     }
-    }
+}
 
-    RemoteStore::Connection * operator -> () { return &*handle; }
+void RemoteStore::ConnectionHandle::processStderr(Sink * sink, Source * source, bool flush)
-    RemoteStore::Connection & operator * () { return *handle; }
+{
-
-    void processStderr(Sink * sink = 0, Source * source = 0, bool flush = true)
-    {
     auto ex = handle->processStderr(sink, source, flush);
     if (ex) {
         daemonException = true;
         std::rethrow_exception(ex);
     }
-    }
+}
-
-    void withFramedSink(std::function<void(Sink & sink)> fun);
-};
 
 
-ConnectionHandle RemoteStore::getConnection()
+RemoteStore::ConnectionHandle RemoteStore::getConnection()
 {
     return ConnectionHandle(connections->get());
 }
@@ -378,27 +354,36 @@ StorePathSet RemoteStore::queryDerivationOutputs(const StorePath & path)
 }
 
 
-std::map<std::string, std::optional<StorePath>> RemoteStore::queryPartialDerivationOutputMap(const StorePath & path)
+std::map<std::string, std::optional<StorePath>> RemoteStore::queryPartialDerivationOutputMap(const StorePath & path, Store * evalStore_)
 {
     if (GET_PROTOCOL_MINOR(getProtocol()) >= 0x16) {
+        if (!evalStore_) {
             auto conn(getConnection());
             conn->to << WorkerProto::Op::QueryDerivationOutputMap << printStorePath(path);
             conn.processStderr();
             return WorkerProto::Serialise<std::map<std::string, std::optional<StorePath>>>::read(*this, *conn);
         } else {
+            auto & evalStore = *evalStore_;
+            auto outputs = evalStore.queryStaticPartialDerivationOutputMap(path);
+            // union with the first branch overriding the statically-known ones
+            // when non-`std::nullopt`.
+            for (auto && [outputName, optPath] : queryPartialDerivationOutputMap(path, nullptr)) {
+                if (optPath)
+                    outputs.insert_or_assign(std::move(outputName), std::move(optPath));
+                else
+                    outputs.insert({std::move(outputName), std::nullopt});
+            }
+            return outputs;
+        }
+    } else {
+        auto & evalStore = evalStore_ ? *evalStore_ : *this;
         // Fallback for old daemon versions.
         // For floating-CA derivations (and their co-dependencies) this is an
         // under-approximation as it only returns the paths that can be inferred
         // from the derivation itself (and not the ones that are known because
         // the have been built), but as old stores don't handle floating-CA
         // derivations this shouldn't matter
-        auto derivation = readDerivation(path);
+        return evalStore.queryStaticPartialDerivationOutputMap(path);
-        auto outputsWithOptPaths = derivation.outputsAndOptPaths(*this);
-        std::map<std::string, std::optional<StorePath>> ret;
-        for (auto & [outputName, outputAndPath] : outputsWithOptPaths) {
-            ret.emplace(outputName, outputAndPath.second);
-        }
-        return ret;
     }
 }
 
@@ -837,15 +822,6 @@ void RemoteStore::addTempRoot(const StorePath & path)
 }
 
 
-void RemoteStore::addIndirectRoot(const Path & path)
-{
-    auto conn(getConnection());
-    conn->to << WorkerProto::Op::AddIndirectRoot << path;
-    conn.processStderr();
-    readInt(conn->from);
-}
-
-
 Roots RemoteStore::findRoots(bool censor)
 {
     auto conn(getConnection());
@@ -1090,7 +1066,7 @@ std::exception_ptr RemoteStore::Connection::processStderr(Sink * sink, Source *
     return nullptr;
 }
 
-void ConnectionHandle::withFramedSink(std::function<void(Sink & sink)> fun)
+void RemoteStore::ConnectionHandle::withFramedSink(std::function<void(Sink & sink)> fun)
 {
     (*this)->to.flush();
 

src/libstore/remote-store.hh

@@ -17,7 +17,6 @@ class Pid;
 struct FdSink;
 struct FdSource;
 template<typename T> class Pool;
-struct ConnectionHandle;
 
 struct RemoteStoreConfig : virtual StoreConfig
 {
@@ -63,7 +62,7 @@ public:
 
     StorePathSet queryDerivationOutputs(const StorePath & path) override;
 
-    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path) override;
+    std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path, Store * evalStore = nullptr) override;
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override;
 
     StorePathSet querySubstitutablePaths(const StorePathSet & paths) override;
@@ -127,8 +126,6 @@ public:
 
     void addTempRoot(const StorePath & path) override;
 
-    void addIndirectRoot(const Path & path) override;
-
     Roots findRoots(bool censor) override;
 
     void collectGarbage(const GCOptions & options, GCResults & results) override;
@@ -182,6 +179,8 @@ protected:
 
     void setOptions() override;
 
+    struct ConnectionHandle;
+
     ConnectionHandle getConnection();
 
     friend struct ConnectionHandle;
@@ -199,5 +198,4 @@ private:
         std::shared_ptr<Store> evalStore);
 };
 
-
 }

src/libstore/ssh-store.cc

@@ -1,5 +1,6 @@
 #include "ssh-store-config.hh"
 #include "store-api.hh"
+#include "local-fs-store.hh"
 #include "remote-store.hh"
 #include "remote-store-connection.hh"
 #include "remote-fs-accessor.hh"
@@ -61,7 +62,7 @@ public:
     std::optional<std::string> getBuildLogExact(const StorePath & path) override
     { unsupported("getBuildLogExact"); }
 
-private:
+protected:
 
     struct Connection : RemoteStore::Connection
     {
@@ -93,9 +94,12 @@ private:
 ref<RemoteStore::Connection> SSHStore::openConnection()
 {
     auto conn = make_ref<Connection>();
-    conn->sshConn = master.startCommand(
+
-        fmt("%s --stdio", remoteProgram)
+    std::string command = remoteProgram + " --stdio";
-        + (remoteStore.get() == "" ? "" : " --store " + shellEscape(remoteStore.get())));
+    if (remoteStore.get() != "")
+        command += " --store " + shellEscape(remoteStore.get());
+
+    conn->sshConn = master.startCommand(command);
     conn->to = FdSink(conn->sshConn->in.get());
     conn->from = FdSource(conn->sshConn->out.get());
     return conn;

src/libstore/store-api.cc

@@ -185,15 +185,15 @@ static std::string makeType(
 
 StorePath Store::makeFixedOutputPath(std::string_view name, const FixedOutputInfo & info) const
 {
-    if (info.hash.hash.type == htSHA256 && info.hash.method == FileIngestionMethod::Recursive) {
+    if (info.hash.type == htSHA256 && info.method == FileIngestionMethod::Recursive) {
-        return makeStorePath(makeType(*this, "source", info.references), info.hash.hash, name);
+        return makeStorePath(makeType(*this, "source", info.references), info.hash, name);
     } else {
         assert(info.references.size() == 0);
         return makeStorePath("output:out",
             hashString(htSHA256,
                 "fixed:out:"
-                + makeFileIngestionPrefix(info.hash.method)
+                + makeFileIngestionPrefix(info.method)
-                + info.hash.hash.to_string(Base16, true) + ":"),
+                + info.hash.to_string(Base16, true) + ":"),
             name);
     }
 }
@@ -201,13 +201,13 @@ StorePath Store::makeFixedOutputPath(std::string_view name, const FixedOutputInf
 
 StorePath Store::makeTextPath(std::string_view name, const TextInfo & info) const
 {
-    assert(info.hash.hash.type == htSHA256);
+    assert(info.hash.type == htSHA256);
     return makeStorePath(
         makeType(*this, "text", StoreReferences {
             .others = info.references,
             .self = false,
         }),
-        info.hash.hash,
+        info.hash,
         name);
 }
 
@@ -233,10 +233,8 @@ std::pair<StorePath, Hash> Store::computeStorePathForPath(std::string_view name,
         ? hashPath(hashAlgo, srcPath, filter).first
         : hashFile(hashAlgo, srcPath);
     FixedOutputInfo caInfo {
-        .hash = {
         .method = method,
         .hash = h,
-        },
         .references = {},
     };
     return std::make_pair(makeFixedOutputPath(name, caInfo), h);
@@ -249,8 +247,8 @@ StorePath Store::computeStorePathForText(
     const StorePathSet & references) const
 {
     return makeTextPath(name, TextInfo {
-        { .hash = hashString(htSHA256, s) },
+        .hash = hashString(htSHA256, s),
-        references,
+        .references = references,
     });
 }
 
@@ -442,10 +440,8 @@ ValidPathInfo Store::addToStoreSlow(std::string_view name, const Path & srcPath,
         *this,
         name,
         FixedOutputInfo {
-            .hash = {
             .method = method,
             .hash = hash,
-            },
             .references = {},
         },
         narHash,
@@ -497,22 +493,50 @@ bool Store::PathInfoCacheValue::isKnownNow()
     return std::chrono::steady_clock::now() < time_point + ttl;
 }
 
-std::map<std::string, std::optional<StorePath>> Store::queryPartialDerivationOutputMap(const StorePath & path)
+std::map<std::string, std::optional<StorePath>> Store::queryStaticPartialDerivationOutputMap(const StorePath & path)
 {
     std::map<std::string, std::optional<StorePath>> outputs;
     auto drv = readInvalidDerivation(path);
-    for (auto& [outputName, output] : drv.outputsAndOptPaths(*this)) {
+    for (auto & [outputName, output] : drv.outputsAndOptPaths(*this)) {
         outputs.emplace(outputName, output.second);
     }
     return outputs;
 }
 
+std::map<std::string, std::optional<StorePath>> Store::queryPartialDerivationOutputMap(
+    const StorePath & path,
+    Store * evalStore_)
+{
+    auto & evalStore = evalStore_ ? *evalStore_ : *this;
+
+    auto outputs = evalStore.queryStaticPartialDerivationOutputMap(path);
+
+    if (!experimentalFeatureSettings.isEnabled(Xp::CaDerivations))
+        return outputs;
+
+    auto drv = evalStore.readInvalidDerivation(path);
+    auto drvHashes = staticOutputHashes(*this, drv);
+    for (auto & [outputName, hash] : drvHashes) {
+        auto realisation = queryRealisation(DrvOutput{hash, outputName});
+        if (realisation) {
+            outputs.insert_or_assign(outputName, realisation->outPath);
+        } else {
+            // queryStaticPartialDerivationOutputMap is not guaranteed
+            // to return std::nullopt for outputs which are not
+            // statically known.
+            outputs.insert({outputName, std::nullopt});
+        }
+    }
+
+    return outputs;
+}
+
 OutputPathMap Store::queryDerivationOutputMap(const StorePath & path) {
     auto resp = queryPartialDerivationOutputMap(path);
     OutputPathMap result;
     for (auto & [outName, optOutPath] : resp) {
         if (!optOutPath)
-            throw Error("output '%s' of derivation '%s' has no store path mapped to it", outName, printStorePath(path));
+            throw MissingRealisation(printStorePath(path), outName);
         result.insert_or_assign(outName, *optOutPath);
     }
     return result;

src/libstore/store-api.hh

@@ -99,6 +99,8 @@ typedef std::map<StorePath, std::optional<ContentAddress>> StorePathCAMap;
 
 struct StoreConfig : public Config
 {
+    typedef std::map<std::string, std::string> Params;
+
     using Config::Config;
 
     StoreConfig() = delete;
@@ -153,10 +155,6 @@ struct StoreConfig : public Config
 
 class Store : public std::enable_shared_from_this<Store>, public virtual StoreConfig
 {
-public:
-
-    typedef std::map<std::string, std::string> Params;
-
 protected:
 
     struct PathInfoCacheValue {
@@ -425,7 +423,20 @@ public:
      * derivation. All outputs are mentioned so ones mising the mapping
      * are mapped to `std::nullopt`.
      */
-    virtual std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(const StorePath & path);
+    virtual std::map<std::string, std::optional<StorePath>> queryPartialDerivationOutputMap(
+        const StorePath & path,
+        Store * evalStore = nullptr);
+
+    /**
+     * Like `queryPartialDerivationOutputMap` but only considers
+     * statically known output paths (i.e. those that can be gotten from
+     * the derivation itself.
+     *
+     * Just a helper function for implementing
+     * `queryPartialDerivationOutputMap`.
+     */
+    virtual std::map<std::string, std::optional<StorePath>> queryStaticPartialDerivationOutputMap(
+        const StorePath & path);
 
     /**
      * Query the mapping outputName=>outputPath for the given derivation.

src/libstore/tests/derivation.cc

@@ -81,7 +81,7 @@ TEST_JSON(DerivationTest, caFixedFlat,
         "path": "/nix/store/rhcg9h16sqvlbpsa6dqm57sbr2al6nzg-drv-name-output-name"
     })",
     (DerivationOutput::CAFixed {
-        .ca = FixedOutputHash {
+        .ca = {
             .method = FileIngestionMethod::Flat,
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
@@ -95,7 +95,7 @@ TEST_JSON(DerivationTest, caFixedNAR,
         "path": "/nix/store/c015dhfh5l0lp6wxyvdn7bmwhbbr6hr9-drv-name-output-name"
     })",
     (DerivationOutput::CAFixed {
-        .ca = FixedOutputHash {
+        .ca = {
             .method = FileIngestionMethod::Recursive,
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
@@ -109,7 +109,7 @@ TEST_JSON(DynDerivationTest, caFixedText,
         "path": "/nix/store/6s1zwabh956jvhv4w9xcdb5jiyanyxg1-drv-name-output-name"
     })",
     (DerivationOutput::CAFixed {
-        .ca = TextHash {
+        .ca = {
             .hash = Hash::parseAnyPrefixed("sha256-iUUXyRY8iW7DGirb0zwGgf1fRbLA7wimTJKgP7l/OQ8="),
         },
     }),

src/libstore/uds-remote-store.cc

@@ -1,4 +1,5 @@
 #include "uds-remote-store.hh"
+#include "worker-protocol.hh"
 
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -77,6 +78,15 @@ ref<RemoteStore::Connection> UDSRemoteStore::openConnection()
 }
 
 
+void UDSRemoteStore::addIndirectRoot(const Path & path)
+{
+    auto conn(getConnection());
+    conn->to << WorkerProto::Op::AddIndirectRoot << path;
+    conn.processStderr();
+    readInt(conn->from);
+}
+
+
 static RegisterStoreImplementation<UDSRemoteStore, UDSRemoteStoreConfig> regUDSRemoteStore;
 
 }

src/libstore/uds-remote-store.hh

@@ -3,13 +3,13 @@
 
 #include "remote-store.hh"
 #include "remote-store-connection.hh"
-#include "local-fs-store.hh"
+#include "indirect-root-store.hh"
 
 namespace nix {
 
 struct UDSRemoteStoreConfig : virtual LocalFSStoreConfig, virtual RemoteStoreConfig
 {
-    UDSRemoteStoreConfig(const Store::Params & params)
+    UDSRemoteStoreConfig(const Params & params)
         : StoreConfig(params)
         , LocalFSStoreConfig(params)
         , RemoteStoreConfig(params)
@@ -21,7 +21,9 @@ struct UDSRemoteStoreConfig : virtual LocalFSStoreConfig, virtual RemoteStoreCon
     std::string doc() override;
 };
 
-class UDSRemoteStore : public virtual UDSRemoteStoreConfig, public virtual LocalFSStore, public virtual RemoteStore
+class UDSRemoteStore : public virtual UDSRemoteStoreConfig
+    , public virtual IndirectRootStore
+    , public virtual RemoteStore
 {
 public:
 
@@ -39,6 +41,16 @@ public:
     void narFromPath(const StorePath & path, Sink & sink) override
     { LocalFSStore::narFromPath(path, sink); }
 
+    /**
+     * Implementation of `IndirectRootStore::addIndirectRoot()` which
+     * delegates to the remote store.
+     *
+     * The idea is that the client makes the direct symlink, so it is
+     * owned managed by the client's user account, and the server makes
+     * the indirect symlink.
+     */
+    void addIndirectRoot(const Path & path) override;
+
 private:
 
     struct Connection : RemoteStore::Connection

src/nix-store/nix-store.cc

@@ -220,10 +220,8 @@ static void opPrintFixedPath(Strings opFlags, Strings opArgs)
     std::string name = *i++;
 
     cout << fmt("%s\n", store->printStorePath(store->makeFixedOutputPath(name, FixedOutputInfo {
-        .hash = {
         .method = method,
         .hash = Hash::parseAny(hash, hashAlgo),
-        },
         .references = {},
     })));
 }

src/nix/add-to-store.cc

@@ -45,10 +45,8 @@ struct CmdAddToStore : MixDryRun, StoreCommand
             *store,
             std::move(*namePart),
             FixedOutputInfo {
-                .hash = {
                 .method = std::move(ingestionMethod),
                 .hash = std::move(hash),
-                },
                 .references = {},
             },
             narHash,

src/nix/prefetch.cc

@@ -71,10 +71,8 @@ std::tuple<StorePath, Hash> prefetchFile(
     if (expectedHash) {
         hashType = expectedHash->type;
         storePath = store->makeFixedOutputPath(*name, FixedOutputInfo {
-            .hash = {
             .method = ingestionMethod,
             .hash = *expectedHash,
-            },
             .references = {},
         });
         if (store->isValidPath(*storePath))
@@ -127,7 +125,7 @@ std::tuple<StorePath, Hash> prefetchFile(
         auto info = store->addToStoreSlow(*name, tmpFile, ingestionMethod, hashType, expectedHash);
         storePath = info.path;
         assert(info.ca);
-        hash = info.ca->getHash();
+        hash = info.ca->hash;
     }
 
     return {storePath.value(), hash.value()};

src/nix/profile.cc

@@ -222,10 +222,8 @@ struct ProfileManifest
             *store,
             "profile",
             FixedOutputInfo {
-                .hash = {
                 .method = FileIngestionMethod::Recursive,
                 .hash = narHash,
-                },
                 .references = {
                     .others = std::move(references),
                     // profiles never refer to themselves

tests/lang/eval-fail-dup-dynamic-attrs.err.exp

@@ -0,0 +1,8 @@
+error: dynamic attribute 'b' already defined at /pwd/lang/eval-fail-dup-dynamic-attrs.nix:2:11
+
+       at /pwd/lang/eval-fail-dup-dynamic-attrs.nix:3:11:
+
+            2|   set = { "${"" + "b"}" = 1; };
+            3|   set = { "${"b" + ""}" = 2; };
+             |           ^
+            4| }

tests/lang/eval-fail-dup-dynamic-attrs.nix

@@ -0,0 +1,4 @@
+{
+  set = { "${"" + "b"}" = 1; };
+  set = { "${"b" + ""}" = 2; };
+}

tests/lang/eval-okay-merge-dynamic-attrs.exp

@@ -0,0 +1 @@
+{ set1 = { a = 1; b = 2; }; set2 = { a = 1; b = 2; }; set3 = { a = 1; b = 2; }; set4 = { a = 1; b = 2; }; }

tests/lang/eval-okay-merge-dynamic-attrs.nix

@@ -0,0 +1,13 @@
+{
+  set1 = { a = 1; };
+  set1 = { "${"b" + ""}" = 2; };
+
+  set2 = { "${"b" + ""}" = 2; };
+  set2 = { a = 1; };
+
+  set3.a = 1;
+  set3."${"b" + ""}" = 2;
+
+  set4."${"b" + ""}" = 2;
+  set4.a = 1;
+}