Use fetchToStore() instead of computeStorePath()

This enables caching of repeated hashing of the same path.
edolstra · May 14, 2024 · a33aad3 · a33aad3
1 parent e255be6
commit a33aad3
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Showing 4 changed files with 25 additions and 16 deletions.
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
@@ -2431,16 +2431,7 @@ StorePath EvalState::copyPathToStore(NixStringContext & context, const SourcePat
                 *store,
                 path.resolveSymlinks(),
                 settings.readOnlyMode ? FetchMode::DryRun : FetchMode::Copy,
-                /* For backwards compatibility, if the path is the
-                   root of a tree, we need to construct a
-                   "double-copied" store path like
-                   /nix/store/<hash1>-<hash2>-source. We don't need to
-                   materialize /nix/store/<hash2>-source
-                   though. Still, this requires reading/hashing the
-                   path twice. */
-                path.path.isRoot()
-                ? store->computeStorePath("source", path).first.to_string()
-                : path.baseName(),
+                computeBaseName(path),
                 FileIngestionMethod::Recursive,
                 nullptr,
                 repair);
@@ -2457,6 +2448,15 @@ StorePath EvalState::copyPathToStore(NixStringContext & context, const SourcePat
 }
 
 
+std::string EvalState::computeBaseName(const SourcePath & path)
+{
+    return std::string(
+        path.path.isRoot()
+        ? fetchToStore(*store, path, FetchMode::DryRun).to_string()
+        : path.baseName());
+}
+
+
 SourcePath EvalState::coerceToPath(const PosIdx pos, Value & v, NixStringContext & context, std::string_view errorCtx)
 {
     try {

diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
@@ -539,6 +539,18 @@ public:
 
     StorePath copyPathToStore(NixStringContext & context, const SourcePath & path);
 
+    /**
+     * Compute the base name for a `SourcePath`. For non-root paths,
+     * this is just `SourcePath::baseName()`. But for root paths, for
+     * backwards compatibility, it needs to be `<hash>-source`,
+     * i.e. as if the path were copied to the Nix store. This results
+     * in a "double-copied" store path like
+     * `/nix/store/<hash1>-<hash2>-source`. We don't need to
+     * materialize /nix/store/<hash2>-source though. Still, this
+     * requires reading/hashing the path twice.
+     */
+    std::string computeBaseName(const SourcePath & path);
+
     /**
      * Path coercion.
      *

diff --git a/src/libexpr/paths.cc b/src/libexpr/paths.cc
@@ -1,6 +1,6 @@
 #include "eval.hh"
 #include "util.hh"
-#include "store-api.hh"
+#include "fetch-to-store.hh"
 
 namespace nix {
 
@@ -123,8 +123,7 @@ std::string EvalState::rewriteVirtualPaths(std::string_view s, std::string_view
                 std::string(warning), // FIXME: should accept a string_view
                 positions[pos], accessor->second->showPath(CanonPath::root));
 
-            // FIXME: cache this.
-            res.append(store->computeStorePath("source", {accessor->second}).first.hashPart());
+            res.append(fetchToStore(*store, {accessor->second}, FetchMode::DryRun).hashPart());
         } catch (...) {
             ignoreException();
             res.append(s.substr(m, end - m));

diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
@@ -2395,9 +2395,7 @@ static void prim_filterSource(EvalState & state, const PosIdx pos, Value * * arg
     addPath(
         state,
         pos,
-        path.path.isRoot()
-        ? state.store->computeStorePath("source", path).first.to_string()
-        : path.baseName(),
+        state.computeBaseName(path),
         path,
         args[0],
         FileIngestionMethod::Recursive,