Backport SourcePath from the lazy-trees branch

This introduces the SourcePath type from lazy-trees as an abstraction
for accessing files from inputs that may not be materialized in the
real filesystem (e.g. Git repositories). Currently, however, it's just
a wrapper around CanonPath, so it shouldn't change any behaviour. (On
lazy-trees, SourcePath is a <InputAccessor, CanonPath> tuple.)

1 files changed, 8 insertions, 3 deletions

diff --git a/src/nix/prefetch.cc b/src/nix/prefetch.cc
index 51c8a3319..039608d48 100644
--- a/src/nix/prefetch.cc
+++ b/src/nix/prefetch.cc
@@ -27,7 +27,10 @@ std::string resolveMirrorUrl(EvalState & state, const std::string & url)
 
     Value vMirrors;
     // FIXME: use nixpkgs flake
-    state.eval(state.parseExprFromString("import <nixpkgs/pkgs/build-support/fetchurl/mirrors.nix>", "."), vMirrors);
+    state.eval(state.parseExprFromString(
+            "import <nixpkgs/pkgs/build-support/fetchurl/mirrors.nix>",
+            state.rootPath(CanonPath::root)),
+        vMirrors);
     state.forceAttrs(vMirrors, noPos, "while evaluating the set of all mirrors");
 
     auto mirrorList = vMirrors.attrs->find(state.symbols.create(mirrorName));
@@ -192,9 +195,11 @@ static int main_nix_prefetch_url(int argc, char * * argv)
                 throw UsageError("you must specify a URL");
             url = args[0];
         } else {
-            Path path = resolveExprPath(lookupFileArg(*state, args.empty() ? "." : args[0]));
             Value vRoot;
-            state->evalFile(path, vRoot);
+            state->evalFile(
+                resolveExprPath(
+                    lookupFileArg(*state, args.empty() ? "." : args[0])),
+                vRoot);
             Value & v(*findAlongAttrPath(*state, attrPath, autoArgs, vRoot).first);
             state->forceAttrs(v, noPos, "while evaluating the source attribute to prefetch");