[8.1.0] Reduce retained memory of UnresolvedSymlinkAction (#24873)

The required conversion to `PathFragment` can be performed during
execution, which avoids retaining a new `PathFragment` instance per
action.

Closes #24831.

PiperOrigin-RevId: 713577830
Change-Id: I2781ea979a3c97abf5a519acd5d3d6a668dd1f77

Commit
293be8a

Co-authored-by: Fabian Meumertzheim <[email protected]>
Co-authored-by: Ian (Hee) Cha <[email protected]>

src/main/java/com/google/devtools/build/lib/analysis/starlark/UnresolvedSymlinkAction.java

@@ -46,16 +46,13 @@
 public final class UnresolvedSymlinkAction extends AbstractAction {
   private static final String GUID = "0f302651-602c-404b-881c-58913193cfe7";
 
-  private final PathFragment target;
+  private final String target;
   private final String progressMessage;
 
   private UnresolvedSymlinkAction(
       ActionOwner owner, Artifact primaryOutput, String target, String progressMessage) {
     super(owner, NestedSetBuilder.emptySet(Order.STABLE_ORDER), ImmutableSet.of(primaryOutput));
-    // TODO: PathFragment#create normalizes the symlink target, which may change how it resolves
-    //  when combined with directory symlinks. Ideally, Bazel's file system abstraction would
-    //  offer a way to create symlinks without any preprocessing of the target.
-    this.target = PathFragment.create(target);
+    this.target = target;
     this.progressMessage = progressMessage;
   }
 
@@ -71,7 +68,7 @@ public ActionResult execute(ActionExecutionContext actionExecutionContext)
 
     Path outputPath = actionExecutionContext.getInputPath(getPrimaryOutput());
     try {
-      outputPath.createSymbolicLink(target);
+      outputPath.createSymbolicLink(getTargetPathFragment());
     } catch (IOException e) {
       String message =
           String.format(
@@ -90,7 +87,7 @@ protected void computeKey(
       @Nullable ArtifactExpander artifactExpander,
       Fingerprint fp) {
     fp.addString(GUID);
-    fp.addPath(target);
+    fp.addString(target);
   }
 
   @Override
@@ -108,8 +105,15 @@ protected String getRawProgressMessage() {
     return progressMessage;
   }
 
-  public PathFragment getTarget() {
-    return target;
+  public String getTarget() {
+    return getTargetPathFragment().getPathString();
+  }
+
+  private PathFragment getTargetPathFragment() {
+    // TODO: PathFragment#create normalizes the symlink target, which may change how it resolves
+    //  when combined with directory symlinks. Ideally, Bazel's file system abstraction would
+    //  offer a way to create symlinks without any preprocessing of the target.
+    return PathFragment.create(target);
   }
 
   private static DetailedExitCode createDetailedExitCode(String message, Code detailedCode) {

src/main/java/com/google/devtools/build/lib/skyframe/actiongraph/v2/ActionGraphDump.java

@@ -212,8 +212,7 @@ private void dumpSingleAction(ConfiguredTarget configuredTarget, ActionAnalysisM
 
 
     if (action instanceof UnresolvedSymlinkAction) {
-      actionBuilder.setUnresolvedSymlinkTarget(
-          ((UnresolvedSymlinkAction) action).getTarget().toString());
+      actionBuilder.setUnresolvedSymlinkTarget(((UnresolvedSymlinkAction) action).getTarget());
     }
 
     // Include the content of param files in output.