Add resolvePath, filesetToSource indirections for Nixpkgs

packaging/dependencies.nix

@@ -14,9 +14,16 @@
 let
   inherit (pkgs) lib;
 
+  root = ../.;
+
+  # Nixpkgs implements this by returning a subpath into the fetched Nix sources.
+  resolvePath = p: p;
+
+  # Indirection for Nixpkgs to override when package.nix files are vendored
+  filesetToSource = lib.fileset.toSource;
+
   localSourceLayer = finalAttrs: prevAttrs:
     let
-      root = ../.;
       workDirPath =
         # Ideally we'd pick finalAttrs.workDir, but for now `mkDerivation` has
         # the requirement that everything except passthru and meta must be
@@ -104,5 +111,7 @@ scope: {
     meta.platforms = lib.platforms.all;
   });
 
+  inherit resolvePath filesetToSource;
+
   mkMesonDerivation = f: stdenv.mkDerivation (lib.extends localSourceLayer f);
 }

tests/unit/libexpr/package.nix

@@ -18,6 +18,7 @@
 # Configuration Options
 
 , version
+, resolvePath
 }:
 
 let
@@ -84,7 +85,7 @@ mkMesonDerivation (finalAttrs: {
       run = runCommand "${finalAttrs.pname}-run" {
       } ''
         PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
-        export _NIX_TEST_UNIT_DATA=${./data}
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
         nix-expr-tests
         touch $out
       '';

tests/unit/libfetchers/package.nix

@@ -17,6 +17,7 @@
 # Configuration Options
 
 , version
+, resolvePath
 }:
 
 let
@@ -82,7 +83,7 @@ mkMesonDerivation (finalAttrs: {
       run = runCommand "${finalAttrs.pname}-run" {
       } ''
         PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
-        export _NIX_TEST_UNIT_DATA=${./data}
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
         nix-fetchers-tests
         touch $out
       '';

tests/unit/libflake/package.nix

@@ -17,6 +17,7 @@
 # Configuration Options
 
 , version
+, resolvePath
 }:
 
 let
@@ -82,7 +83,7 @@ mkMesonDerivation (finalAttrs: {
       run = runCommand "${finalAttrs.pname}-run" {
       } ''
         PATH="${lib.makeBinPath [ finalAttrs.finalPackage ]}:$PATH"
-        export _NIX_TEST_UNIT_DATA=${./data}
+        export _NIX_TEST_UNIT_DATA=${resolvePath ./data}
         nix-flake-tests
         touch $out
       '';

tests/unit/libstore/package.nix

@@ -19,6 +19,7 @@
 # Configuration Options
 
 , version
+, filesetToSource
 }:
 
 let
@@ -86,7 +87,7 @@ mkMesonDerivation (finalAttrs: {
       run = let
         # Some data is shared with the functional tests: they create it,
         # we consume it.
-        data = lib.fileset.toSource {
+        data = filesetToSource {
           root = ../..;
           fileset = lib.fileset.unions [
             ./data