Normalize the hash-rewriting process when building derivations

NixOS · Mar 17, 2023 · a5c970a · a5c970a
1 parent c9d77b0
commit a5c970a
Showing 1 changed file with 13 additions and 15 deletions.
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
@@ -2361,14 +2361,14 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
             continue;
         auto references = *referencesOpt;
 
-        auto rewriteOutput = [&]() {
+        auto rewriteOutput = [&](const StringMap & rewrites) {
             /* Apply hash rewriting if necessary. */
-            if (!outputRewrites.empty()) {
+            if (!rewrites.empty()) {
                 debug("rewriting hashes in '%1%'; cross fingers", actualPath);
 
                 /* FIXME: Is this actually streaming? */
                 auto source = sinkToSource([&](Sink & nextSink) {
-                    RewritingSink rsink(outputRewrites, nextSink);
+                    RewritingSink rsink(rewrites, nextSink);
                     dumpPath(actualPath, rsink);
                     rsink.flush();
                 });
@@ -2423,7 +2423,7 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
                         "since recursive hashing is not enabled (outputHashMode=flat)",
                         actualPath);
             }
-            rewriteOutput();
+            rewriteOutput(outputRewrites);
             /* FIXME optimize and deduplicate with addToStore */
             std::string oldHashPart { scratchPath->hashPart() };
             HashModuloSink caSink { outputHash.hashType, oldHashPart };
@@ -2445,16 +2445,14 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
                     refs.second,
                     refs.first);
             if (*scratchPath != finalPath) {
-                // Also rewrite the output path
-                auto source = sinkToSource([&](Sink & nextSink) {
-                    RewritingSink rsink2(oldHashPart, std::string(finalPath.hashPart()), nextSink);
-                    dumpPath(actualPath, rsink2);
-                    rsink2.flush();
-                });
-                Path tmpPath = actualPath + ".tmp";
-                restorePath(tmpPath, *source);
-                deletePath(actualPath);
-                movePath(tmpPath, actualPath);
+                // If the path has some self-references, we need to rewrite
+                // them.
+                // (note that this doesn't invalidate the ca hash we calculated
+                // above because it's computed *modulo the self-references*, so
+                // it already takes this rewrite into account).
+                rewriteOutput(
+                    StringMap{{oldHashPart,
+                               std::string(finalPath.hashPart())}});
             }
 
             HashResult narHashAndSize = hashPath(htSHA256, actualPath);
@@ -2487,7 +2485,7 @@ DrvOutputs LocalDerivationGoal::registerOutputs()
                     outputRewrites.insert_or_assign(
                         std::string { scratchPath->hashPart() },
                         std::string { requiredFinalPath.hashPart() });
-                rewriteOutput();
+                rewriteOutput(outputRewrites);
                 auto narHashAndSize = hashPath(htSHA256, actualPath);
                 ValidPathInfo newInfo0 { requiredFinalPath, narHashAndSize.first };
                 newInfo0.narSize = narHashAndSize.second;