libstore/gc: restore deletion of referrers

Fixes: 8614cf1334
Fixes #495

Change-Id: I4d8d655c6254786ba1222a5b37551c68d9e370ee

doc/manual/rl-next/delete-referrers.md

@@ -0,0 +1,13 @@
+---
+synopsis: "Fix nix-store --delete on paths with remaining referrers"
+cls: [2783]
+category: "Fixes"
+credits: lheckemann
+---
+
+Nix 2.5 introduced a regression whereby `nix-store --delete` and `nix
+store delete` started to fail when trying to delete a path that was
+still referenced by other paths, even if the referrers were not
+reachable from any GC roots. The old behaviour, where attempting to
+delete a store path would also delete its referrer closure, is now
+restored.

lix/libstore/gc.cc

@@ -749,10 +749,6 @@ try {
                     co_return result::success();
                 }
 
-                if (options.action == GCOptions::gcDeleteSpecific
-                    && !options.pathsToDelete.count(*path))
-                    co_return result::success();
-
                 if (!gcServer.markPendingIfPresent(std::string(path->hashPart()))) {
                     debug("cannot delete '%s' because it's a temporary root", printStorePath(*path));
                     TRY_AWAIT(markAlive());

tests/functional/gc.sh

@@ -2,12 +2,16 @@ source common.sh
 
 clearStore
 
-drvPath=$(nix-instantiate dependencies.nix)
-outPath=$(nix-store -rvv "$drvPath")
+createAndRootPaths() {
+  drvPath=$(nix-instantiate dependencies.nix)
+  outPath=$(nix-store -rvv "$drvPath")
 
-# Set a GC root.
-rm -f "$NIX_STATE_DIR"/gcroots/foo
-ln -sf $outPath "$NIX_STATE_DIR"/gcroots/foo
+  # Set a GC root.
+  rm -f "$NIX_STATE_DIR"/gcroots/foo
+  ln -sf $outPath "$NIX_STATE_DIR"/gcroots/foo
+}
+
+createAndRootPaths
 
 [ "$(nix-store -q --roots $outPath)" = "$NIX_STATE_DIR/gcroots/foo -> $outPath" ]
 
@@ -18,9 +22,9 @@ if nix-store --gc --print-dead | grep -E $outPath$; then false; fi
 
 nix-store --gc --print-dead
 
-inUse=$(readLink $outPath/reference-to-input-2)
-if nix-store --delete $inUse; then false; fi
-test -e $inUse
+input2=$(readLink $outPath/reference-to-input-2)
+if nix-store --delete $input2; then false; fi
+test -e $input2
 
 if nix-store --delete $outPath; then false; fi
 test -e $outPath
@@ -42,10 +46,14 @@ if test -e $drvPath; then false; fi
 
 rm "$NIX_STATE_DIR"/gcroots/foo
 
-nix-collect-garbage
+# Deleting the dependency should now be possible, and delete the referrer as well
+nix-store --delete $input2
+! test -e $outPath
+! test -e $input2
 
-# Check that the output has been GC'd.
-if test -e $outPath/foobar; then false; fi
+createAndRootPaths
+rm "$NIX_STATE_DIR"/gcroots/foo
+nix-collect-garbage
 
 # Check that the store is empty.
 rmdir $NIX_STORE_DIR/.links