cargoTomlContents: ignore context of Cargo.toml file (#762)

CHANGELOG.md

@@ -19,6 +19,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 * `mkDummySrc` will deduplicate discovered and declared binary targets when
   dummifying sources
+* `crateNameFromCargoToml` will ignore store contexts when parsing a Cargo.toml
+  file (avoiding errors like `the string ... is not allowed to refer to a store
+  path`).
 
 ### Meta
 * Dropped support for publishing releases to https://flakestry.dev/

checks/default.nix

@@ -274,6 +274,15 @@ in
     };
   };
 
+  customDummyWithMkDummySrcNoPname = myLib.buildDepsOnly {
+    dummySrc = myLib.mkDummySrc {
+      src = myLib.cleanCargoSource ./simple;
+      postInstall = ''
+        touch $out/blah.txt
+      '';
+    };
+  };
+
   # https://github.com/ipetkov/crane/pull/234
   nonJsonCargoBuildLog =
     let

lib/crateNameFromCargoToml.nix

@@ -25,7 +25,12 @@ let
     else throwMsg
   );
 
-  toml = builtins.fromTOML cargoTomlContents;
+  # NB: if `src` is derived via `mkDummySrc` the Cargo.toml will contain store paths
+  # (e.g. build script stubs), which the fromTOML does not like since the context isn't
+  # threaded through (error is `the string ... is not allowed to refer to a store path`).
+  # We can work around this by discarding the context before parsing the TOML since we don't
+  # actually care about any dependency derivations, we just want to parse the name and version
+  toml = builtins.fromTOML (builtins.unsafeDiscardStringContext cargoTomlContents);
 
   debugPath =
     if args ? cargoTomlContents