Follow symlinks for setLastModifiedTime.

The method is documented as such in FileSystem.

PiperOrigin-RevId: 585581298
Change-Id: I9838d97747f820784db2f9fd68425d4d27b8b857

src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java

@@ -335,6 +335,8 @@ protected SeekableByteChannel createReadWriteByteChannel(PathFragment path) thro
 
   @Override
   public void setLastModifiedTime(PathFragment path, long newTime) throws IOException {
+    path = resolveSymbolicLinks(path).asFragment();
+
     FileNotFoundException remoteException = null;
     try {
       // We can't set mtime for a remote file, set mtime of in-memory file node instead.

src/test/java/com/google/devtools/build/lib/remote/RemoteActionFileSystemTest.java

@@ -460,6 +460,51 @@ public void statAndExists_notFound() throws Exception {
         FileNotFoundException.class, () -> actionFs.stat(path, /* followSymlinks= */ true));
   }
 
+  @Test
+  public void setLastModifiedTime_forRemoteOutputTree() throws Exception {
+    RemoteActionFileSystem actionFs = (RemoteActionFileSystem) createActionFileSystem();
+    Artifact artifact = ActionsTestUtil.createArtifact(outputRoot, "out");
+    PathFragment path = artifact.getPath().asFragment();
+    injectRemoteFile(actionFs, artifact.getPath().asFragment(), "remote contents");
+
+    actionFs.getPath(path).setLastModifiedTime(1234567890);
+    assertThat(actionFs.getPath(path).getLastModifiedTime()).isEqualTo(1234567890);
+  }
+
+  @Test
+  public void setLastModifiedTime_forLocalFilesystem() throws Exception {
+    RemoteActionFileSystem actionFs = (RemoteActionFileSystem) createActionFileSystem();
+    Artifact artifact = ActionsTestUtil.createArtifact(outputRoot, "out");
+    PathFragment path = artifact.getPath().asFragment();
+    writeLocalFile(actionFs, artifact.getPath().asFragment(), "local contents");
+
+    actionFs.getPath(path).setLastModifiedTime(1234567890);
+    assertThat(actionFs.getPath(path).getLastModifiedTime()).isEqualTo(1234567890);
+  }
+
+  @Test
+  public void setLastModifiedTime_followSymlinks(
+      @TestParameter FilesystemTestParam from, @TestParameter FilesystemTestParam to)
+      throws Exception {
+    RemoteActionFileSystem actionFs = (RemoteActionFileSystem) createActionFileSystem();
+    FileSystem fromFs = from.getFilesystem(actionFs);
+    FileSystem toFs = to.getFilesystem(actionFs);
+
+    PathFragment linkPath = getOutputPath("sym");
+    PathFragment targetPath = getOutputPath("target");
+    fromFs.getPath(linkPath).createSymbolicLink(execRoot.getRelative(targetPath).asFragment());
+
+    if (toFs.equals(actionFs.getLocalFileSystem())) {
+      writeLocalFile(actionFs, targetPath, "content");
+    } else {
+      injectRemoteFile(actionFs, targetPath, "content");
+    }
+
+    actionFs.getPath(linkPath).setLastModifiedTime(1234567890);
+    assertThat(actionFs.getPath(linkPath).getLastModifiedTime()).isEqualTo(1234567890);
+    assertThat(actionFs.getPath(targetPath).getLastModifiedTime()).isEqualTo(1234567890);
+  }
+
   @Test
   public void getDigest_fromInputArtifactData_forLocalArtifact() throws Exception {
     ActionInputMap inputs = new ActionInputMap(1);