From a218dd80d6907246dc56b248f6941d29743c304c Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 16 Aug 2022 16:05:43 +0200
Subject: [PATCH] Support locking path inputs

---
 src/libfetchers/fetchers.cc  |  5 -----
 src/libfetchers/path.cc      | 38 +++++++++++++++++++++++++++++++++---
 tests/flakes/flakes.sh       | 11 +++++------
 tests/flakes/follow-paths.sh | 10 +++-------
 4 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/src/libfetchers/fetchers.cc b/src/libfetchers/fetchers.cc
index 9347da86e..33a36338c 100644
--- a/src/libfetchers/fetchers.cc
+++ b/src/libfetchers/fetchers.cc
@@ -134,11 +134,6 @@ std::pair<StorePath, Input> Input::fetchToStore(ref<Store> store) const
 
 void Input::checkLocks(Input & input) const
 {
-    #if 0
-    auto narHash = store.queryPathInfo(storePath)->narHash;
-    input.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
-    #endif
-
     if (auto prevNarHash = getNarHash()) {
         if (input.getNarHash() != prevNarHash)
             throw Error((unsigned int) 102, "NAR hash mismatch in input '%s', expected '%s'",
diff --git a/src/libfetchers/path.cc b/src/libfetchers/path.cc
index 3cb4dad02..72596841f 100644
--- a/src/libfetchers/path.cc
+++ b/src/libfetchers/path.cc
@@ -27,6 +27,8 @@ struct PathInputScheme : InputScheme
                 else
                     throw Error("path URL '%s' has invalid parameter '%s'", url.to_string(), name);
             }
+            else if (name == "lock")
+                input.attrs.emplace(name, Explicit<bool> { value == "1" });
             else
                 throw Error("path URL '%s' has unsupported parameter '%s'", url.to_string(), name);
 
@@ -38,6 +40,7 @@ struct PathInputScheme : InputScheme
         if (maybeGetStrAttr(attrs, "type") != "path") return {};
 
         getStrAttr(attrs, "path");
+        maybeGetBoolAttr(attrs, "lock");
 
         for (auto & [name, value] : attrs)
             /* Allow the user to pass in "fake" tree info
@@ -47,8 +50,8 @@ struct PathInputScheme : InputScheme
                FIXME: remove this hack once we have a prepopulated
                flake input cache mechanism.
             */
-            if (name == "type" || name == "rev" || name == "revCount" || name == "lastModified" || name == "narHash" || name == "path")
-                // checked in Input::fromAttrs
+            if (name == "type" || name == "rev" || name == "revCount" || name == "lastModified" || name == "narHash" || name == "path" || name == "lock")
+                // checked elsewhere
                 ;
             else
                 throw Error("unsupported path input attribute '%s'", name);
@@ -58,6 +61,11 @@ struct PathInputScheme : InputScheme
         return input;
     }
 
+    bool getLockAttr(const Input & input) const
+    {
+        return maybeGetBoolAttr(input.attrs, "lock").value_or(false);
+    }
+
     ParsedURL toURL(const Input & input) const override
     {
         auto query = attrsToQuery(input.attrs);
@@ -112,7 +120,31 @@ struct PathInputScheme : InputScheme
         auto absPath = getAbsPath(input);
         auto input2(input);
         input2.attrs.emplace("path", (std::string) absPath.abs());
-        return {makeFSInputAccessor(absPath), std::move(input2)};
+
+        if (getLockAttr(input2)) {
+
+            auto storePath = store->maybeParseStorePath(absPath.abs());
+
+            if (!storePath || storePath->name() != input.getName() || !store->isValidPath(*storePath)) {
+                Activity act(*logger, lvlChatty, actUnknown, fmt("copying '%s' to the store", absPath));
+                storePath = store->addToStore(input.getName(), absPath.abs());
+                auto narHash = store->queryPathInfo(*storePath)->narHash;
+                input2.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
+            } else
+                input2.attrs.erase("narHash");
+
+            input2.attrs.erase("lastModified");
+
+            auto makeNotAllowedError = [absPath](const CanonPath & path) -> RestrictedPathError
+            {
+                return RestrictedPathError("path '%s' does not exist'", absPath + path);
+            };
+
+            return {makeStorePathAccessor(store, *storePath, std::move(makeNotAllowedError)), std::move(input2)};
+
+        } else {
+            return {makeFSInputAccessor(absPath), std::move(input2)};
+        }
     }
 
     std::optional<std::string> getFingerprint(ref<Store> store, const Input & input) const override
diff --git a/tests/flakes/flakes.sh b/tests/flakes/flakes.sh
index 8cdb26231..f998dab19 100644
--- a/tests/flakes/flakes.sh
+++ b/tests/flakes/flakes.sh
@@ -221,11 +221,10 @@ cat > $flake3Dir/flake.nix <<EOF
       url = git+file://$nonFlakeDir;
       flake = false;
     };
-    # FIXME: we can't lock path:// inputs at the moment.
-    #nonFlakeFile = {
-    #  url = path://$nonFlakeDir/README.md;
-    #  flake = false;
-    #};
+    nonFlakeFile = {
+      url = path://$nonFlakeDir/README.md?lock=1;
+      flake = false;
+    };
     #nonFlakeFile2 = {
     #  url = "$nonFlakeDir/README.md";
     #  flake = false;
@@ -246,8 +245,8 @@ cat > $flake3Dir/flake.nix <<EOF
         dummy2 = builtins.readFile (builtins.path { name = "source"; path = inputs.flake1; filter = path: type: baseNameOf path == "simple.nix"; } + "/simple.nix");
         buildCommand = ''
           cat \${inputs.nonFlake}/README.md > \$out
+          [[ \$(cat \${inputs.nonFlake}/README.md) = \$(cat \${inputs.nonFlakeFile}) ]]
         '';
-        #  [[ \$(cat \${inputs.nonFlake}/README.md) = \$(cat \${inputs.nonFlakeFile}) ]]
         #  [[ \${inputs.nonFlakeFile} = \${inputs.nonFlakeFile2} ]]
       };
   };
diff --git a/tests/flakes/follow-paths.sh b/tests/flakes/follow-paths.sh
index 6b0cb6cba..737ba30a4 100644
--- a/tests/flakes/follow-paths.sh
+++ b/tests/flakes/follow-paths.sh
@@ -27,9 +27,7 @@ cat > $flakeFollowsA/flake.nix <<EOF
             inputs.foobar.follows = "foobar";
         };
 
-        # FIXME: currently absolute path: flakes cannot be locked.
-        #foobar.url = "path:$flakeFollowsA/flakeE";
-        foobar.url = "git+file://$flake1Dir";
+        foobar.url = "path:$flakeFollowsA/flakeE?lock=1";
     };
     outputs = { ... }: {};
 }
@@ -39,8 +37,7 @@ cat > $flakeFollowsB/flake.nix <<EOF
 {
     description = "Flake B";
     inputs = {
-        #foobar.url = "path:$flakeFollowsA/flakeE";
-        foobar.url = "git+file://$flake1Dir";
+        foobar.url = "path:$flakeFollowsA/flakeE?lock=1";
         goodoo.follows = "C/goodoo";
         C = {
             url = "path:./flakeC";
@@ -55,8 +52,7 @@ cat > $flakeFollowsC/flake.nix <<EOF
 {
     description = "Flake C";
     inputs = {
-        #foobar.url = "path:$flakeFollowsA/flakeE";
-        foobar.url = "git+file://$flake1Dir";
+        foobar.url = "path:$flakeFollowsA/flakeE?lock=1";
         goodoo.follows = "foobar";
     };
     outputs = { ... }: {};