Make nix path-info --json return an object not array

Before it returned a list of JSON objects with store object information,
including the path in each object. Now, it maps the paths to JSON
objects with the metadata sans path.

This matches how `nix derivation show` works.

Quite hillariously, none of our existing functional tests caught this
change to `path-info --json` though they did use it. So just new
functional tests need to be added.

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

@@ -28,5 +28,39 @@
 
   - The flake-specific flags `--recreate-lock-file` and `--update-input` have been removed from all commands operating on installables.
     They are superceded by `nix flake update`.
-  
+
 - Commit signature verification for the [`builtins.fetchGit`](@docroot@/language/builtins.md#builtins-fetchGit) is added as the new [`verified-fetches` experimental feature](@docroot@/contributing/experimental-features.md#xp-feature-verified-fetches).
+
+- [`nix path-info --json`](@docroot@/command-ref/new-cli/nix3-path-info.md)
+  (experimental) now returns a JSON map rather than JSON list.
+  The `path` field of each object has instead become the key in th outer map, since it is unique.
+  The `valid` field also goes away because we just use null instead.
+
+  - Old way:
+
+    ```json5
+    [
+      {
+        "path": "/nix/store/8fv91097mbh5049i9rglc73dx6kjg3qk-bash-5.2-p15",
+        "valid": true,
+        // ...
+      },
+      {
+        "path": "/nix/store/wffw7l0alvs3iw94cbgi1gmmbmw99sqb-home-manager-path",
+        "valid": false
+      }
+    ]
+    ```
+
+  - New way
+
+    ```json5
+    {
+      "/nix/store/8fv91097mbh5049i9rglc73dx6kjg3qk-bash-5.2-p15": {
+        // ...
+      },
+      "/nix/store/wffw7l0alvs3iw94cbgi1gmmbmw99sqb-home-manager-path": null,
+    }
+    ```
+
+  This makes it match `nix derivation show`, which also maps store paths to information.

src/libstore/nar-info.cc

@@ -164,8 +164,12 @@ NarInfo NarInfo::fromJSON(
 {
     using nlohmann::detail::value_t;
 
-    NarInfo res { ValidPathInfo::fromJSON(store, json) };
+    NarInfo res {
-    res.path = path;
+        ValidPathInfo {
+            path,
+            UnkeyedValidPathInfo::fromJSON(store, json),
+        }
+    };
 
     if (json.contains("url"))
         res.url = ensureType(valueAt(json, "url"), value_t::string);

src/libstore/parsed-derivations.cc

@@ -148,6 +148,11 @@ static nlohmann::json pathInfoToJSON(
         auto & jsonPath = jsonList.emplace_back(
             info->toJSON(store, false, HashFormat::Base32));
 
+        // Add the path to the object whose metadata we are including.
+        jsonPath["path"] = store.printStorePath(storePath);
+
+        jsonPath["valid"] = true;
+
         jsonPath["closureSize"] = ({
             uint64_t totalNarSize = 0;
             StorePathSet closure;

src/libstore/path-info.cc

@@ -148,7 +148,7 @@ ValidPathInfo::ValidPathInfo(
 }
 
 
-nlohmann::json ValidPathInfo::toJSON(
+nlohmann::json UnkeyedValidPathInfo::toJSON(
     const Store & store,
     bool includeImpureInfo,
     HashFormat hashFormat) const
@@ -157,8 +157,6 @@ nlohmann::json ValidPathInfo::toJSON(
 
     auto jsonObject = json::object();
 
-    jsonObject["path"] = store.printStorePath(path);
-    jsonObject["valid"] = true;
     jsonObject["narHash"] = narHash.to_string(hashFormat, true);
     jsonObject["narSize"] = narSize;
 
@@ -190,21 +188,17 @@ nlohmann::json ValidPathInfo::toJSON(
     return jsonObject;
 }
 
-ValidPathInfo ValidPathInfo::fromJSON(
+UnkeyedValidPathInfo UnkeyedValidPathInfo::fromJSON(
     const Store & store,
     const nlohmann::json & json)
 {
     using nlohmann::detail::value_t;
 
-    ValidPathInfo res {
+    UnkeyedValidPathInfo res {
-        StorePath(StorePath::dummy),
         Hash(Hash::dummy),
     };
 
     ensureType(json, value_t::object);
-    res.path = store.parseStorePath(
-        static_cast<const std::string &>(
-            ensureType(valueAt(json, "path"), value_t::string)));
     res.narHash = Hash::parseAny(
         static_cast<const std::string &>(
             ensureType(valueAt(json, "narHash"), value_t::string)),

src/libstore/path-info.hh

@@ -78,6 +78,18 @@ struct UnkeyedValidPathInfo
     DECLARE_CMP(UnkeyedValidPathInfo);
 
     virtual ~UnkeyedValidPathInfo() { }
+
+    /**
+     * @param includeImpureInfo If true, variable elements such as the
+     * registration time are included.
+     */
+    virtual nlohmann::json toJSON(
+        const Store & store,
+        bool includeImpureInfo,
+        HashFormat hashFormat) const;
+    static UnkeyedValidPathInfo fromJSON(
+        const Store & store,
+        const nlohmann::json & json);
 };
 
 struct ValidPathInfo : UnkeyedValidPathInfo {
@@ -125,18 +137,6 @@ struct ValidPathInfo : UnkeyedValidPathInfo {
 
     Strings shortRefs() const;
 
-    /**
-     * @param includeImpureInfo If true, variable elements such as the
-     * registration time are included.
-     */
-    virtual nlohmann::json toJSON(
-        const Store & store,
-        bool includeImpureInfo,
-        HashFormat hashFormat) const;
-    static ValidPathInfo fromJSON(
-        const Store & store,
-        const nlohmann::json & json);
-
     ValidPathInfo(const ValidPathInfo & other) = default;
 
     ValidPathInfo(StorePath && path, UnkeyedValidPathInfo info) : UnkeyedValidPathInfo(info), path(std::move(path)) { };

src/libstore/tests/path-info.cc

@@ -19,8 +19,8 @@ class PathInfoTest : public CharacterizationTest, public LibStoreTest
     }
 };
 
-static ValidPathInfo makePathInfo(const Store & store, bool includeImpureInfo) {
+static UnkeyedValidPathInfo makePathInfo(const Store & store, bool includeImpureInfo) {
-    ValidPathInfo info {
+    UnkeyedValidPathInfo info = ValidPathInfo {
         store,
         "foo",
         FixedOutputInfo {
@@ -54,7 +54,7 @@ static ValidPathInfo makePathInfo(const Store & store, bool includeImpureInfo) {
     TEST_F(PathInfoTest, PathInfo_ ## STEM ## _from_json) {               \
         readTest(#STEM, [&](const auto & encoded_) {                      \
             auto encoded = json::parse(encoded_);                         \
-            ValidPathInfo got = ValidPathInfo::fromJSON(                  \
+            UnkeyedValidPathInfo got = UnkeyedValidPathInfo::fromJSON(    \
                 *store,                                                   \
                 encoded);                                                 \
             auto expected = makePathInfo(*store, PURE);                   \

src/nix/path-info.cc

@@ -38,20 +38,21 @@ static json pathInfoToJSON(
     const StorePathSet & storePaths,
     bool showClosureSize)
 {
-    json::array_t jsonList = json::array();
+    json::object_t jsonAllObjects = json::object();
 
     for (auto & storePath : storePaths) {
+        json jsonObject;
+
         try {
             auto info = store.queryPathInfo(storePath);
 
-            auto & jsonPath = jsonList.emplace_back(
+            jsonObject = info->toJSON(store, true, HashFormat::SRI);
-                info->toJSON(store, true, HashFormat::SRI));
 
             if (showClosureSize) {
                 StorePathSet closure;
                 store.computeFSClosure(storePath, closure, false, false);
 
-                jsonPath["closureSize"] = getStoreObjectsTotalSize(store, closure);
+                jsonObject["closureSize"] = getStoreObjectsTotalSize(store, closure);
 
                 if (auto * narInfo = dynamic_cast<const NarInfo *>(&*info)) {
                     uint64_t totalDownloadSize = 0;
@@ -64,17 +65,17 @@ static json pathInfoToJSON(
                                 store.printStorePath(p),
                                 store.printStorePath(storePath));
                     }
-                    jsonPath["closureDownloadSize"] = totalDownloadSize;
+                    jsonObject["closureDownloadSize"] = totalDownloadSize;
                 }
             }
 
         } catch (InvalidPath &) {
-            auto & jsonPath = jsonList.emplace_back(json::object());
+            jsonObject = nullptr;
-            jsonPath["path"] = store.printStorePath(storePath);
-            jsonPath["valid"] = false;
         }
+
+        jsonAllObjects[store.printStorePath(storePath)] = std::move(jsonObject);
     }
-    return jsonList;
+    return jsonAllObjects;
 }
 
 

src/nix/path-info.md

@@ -43,7 +43,7 @@ R""(
   command):
 
   ```console
-  # nix path-info --json --all | jq -r 'sort_by(.registrationTime)[-11:-1][].path'
+  # nix path-info --json --all | jq -r 'to_entries | sort_by(.value.registrationTime) | .[-11:-1][] | .key'
   ```
 
 * Show the size of the entire Nix store:
@@ -58,13 +58,13 @@ R""(
 
   ```console
   # nix path-info --json --all --closure-size \
-    | jq 'map(select(.closureSize > 1e9)) | sort_by(.closureSize) | map([.path, .closureSize])'
+    | jq 'map_values(.closureSize | select(. < 1e9)) | to_entries | sort_by(.value)'
   [
     …,
-    [
+    {
-      "/nix/store/zqamz3cz4dbzfihki2mk7a63mbkxz9xq-nixos-system-machine-20.09.20201112.3090c65",
+      .key = "/nix/store/zqamz3cz4dbzfihki2mk7a63mbkxz9xq-nixos-system-machine-20.09.20201112.3090c65",
-      5887562256
+      .value = 5887562256,
-    ]
+    }
   ]
   ```
 

tests/functional/local.mk

@@ -120,6 +120,7 @@ nix_tests = \
   flakes/show.sh \
   impure-derivations.sh \
   path-from-hash-part.sh \
+  path-info.sh \
   toString-path.sh \
   read-only-store.sh \
   nested-sandboxing.sh \

tests/functional/path-info.sh

@@ -0,0 +1,23 @@
+source common.sh
+
+echo foo > $TEST_ROOT/foo
+foo=$(nix store add-file $TEST_ROOT/foo)
+
+echo bar > $TEST_ROOT/bar
+bar=$(nix store add-file $TEST_ROOT/bar)
+
+echo baz > $TEST_ROOT/baz
+baz=$(nix store add-file $TEST_ROOT/baz)
+nix-store --delete "$baz"
+
+diff --unified --color=always \
+    <(nix path-info --json "$foo" "$bar" "$baz" |
+        jq --sort-keys 'map_values(.narHash)') \
+    <(jq --sort-keys <<-EOF
+        {
+          "$foo": "sha256-QvtAMbUl/uvi+LCObmqOhvNOapHdA2raiI4xG5zI5pA=",
+          "$bar": "sha256-9fhYGu9fqxcQC2Kc81qh2RMo1QcLBUBo8U+pPn+jthQ=",
+          "$baz": null
+        }
+EOF
+    )

unit-test-data/libstore/nar-info/impure.json

@@ -6,7 +6,6 @@
   "downloadSize": 4029176,
   "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
-  "path": "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo",
   "references": [
     "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo"
@@ -17,6 +16,5 @@
     "qwer"
   ],
   "ultimate": true,
-  "url": "nar/1w1fff338fvdw53sqgamddn1b2xgds473pv6y13gizdbqjv4i5p3.nar.xz",
+  "url": "nar/1w1fff338fvdw53sqgamddn1b2xgds473pv6y13gizdbqjv4i5p3.nar.xz"
-  "valid": true
 }

unit-test-data/libstore/nar-info/pure.json

@@ -2,10 +2,8 @@
   "ca": "fixed:r:sha256:1lr187v6dck1rjh2j6svpikcfz53wyl3qrlcbb405zlh13x0khhh",
   "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
-  "path": "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo",
   "references": [
     "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo"
-  ],
+  ]
-  "valid": true
 }

unit-test-data/libstore/path-info/impure.json

@@ -3,7 +3,6 @@
   "deriver": "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar.drv",
   "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
-  "path": "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo",
   "references": [
     "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo"
@@ -13,6 +12,5 @@
     "asdf",
     "qwer"
   ],
-  "ultimate": true,
+  "ultimate": true
-  "valid": true
 }

unit-test-data/libstore/path-info/pure.json

@@ -2,10 +2,8 @@
   "ca": "fixed:r:sha256:1lr187v6dck1rjh2j6svpikcfz53wyl3qrlcbb405zlh13x0khhh",
   "narHash": "sha256-FePFYIlMuycIXPZbWi7LGEiMmZSX9FMbaQenWBzm1Sc=",
   "narSize": 34878,
-  "path": "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo",
   "references": [
     "/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-bar",
     "/nix/store/n5wkd9frr45pa74if5gpz9j7mifg27fh-foo"
-  ],
+  ]
-  "valid": true
 }