From 03469cc788d7f4895bfea3ea202dd0f53393f2fb Mon Sep 17 00:00:00 2001
From: Googler <chiwang@google.com>
Date: Fri, 5 May 2023 02:02:59 -0700
Subject: [PATCH] Fix crash in BwoB when creating symlink to source files.

Fixes https://github.com/bazelbuild/bazel/issues/18321.

PiperOrigin-RevId: 529656152
Change-Id: I06c60282893ef57dea837864031da0fe522937b8
---
 .../lib/remote/RemoteActionFileSystem.java    |  5 +++-
 .../BuildWithoutTheBytesIntegrationTest.java  | 28 +++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java b/src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java
index 295c70ec7771f8..7e4096b7fb3e5d 100644
--- a/src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java
+++ b/src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java
@@ -185,7 +185,10 @@ private void maybeInjectMetadataForSymlinkOrDownload(PathFragment linkPath, Arti
         targetPath.isAbsolute(),
         "non-symlink artifact materialized as symlink must point to absolute path");
 
-    if (inputFetcher.getRemoteOutputChecker().shouldDownloadOutputDuringActionExecution(output)) {
+    if (isOutput(targetPath)
+        && inputFetcher
+            .getRemoteOutputChecker()
+            .shouldDownloadOutputDuringActionExecution(output)) {
       var targetActionInput = getInput(targetPath.relativeTo(execRoot).getPathString());
       if (targetActionInput != null) {
         if (output.isTreeArtifact()) {
diff --git a/src/test/java/com/google/devtools/build/lib/remote/BuildWithoutTheBytesIntegrationTest.java b/src/test/java/com/google/devtools/build/lib/remote/BuildWithoutTheBytesIntegrationTest.java
index a1aa27e5573579..ffecdfb109b082 100644
--- a/src/test/java/com/google/devtools/build/lib/remote/BuildWithoutTheBytesIntegrationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/remote/BuildWithoutTheBytesIntegrationTest.java
@@ -723,6 +723,34 @@ public void downloadToplevel_symlinkFile() throws Exception {
     assertValidOutputFile("foo-link", "foo\n");
   }
 
+  @Test
+  public void downloadToplevel_symlinkSourceFile() throws Exception {
+    // TODO(chiwang): Make metadata for downloaded symlink non-remote.
+    assumeFalse(OS.getCurrent() == OS.WINDOWS);
+
+    setDownloadToplevel();
+    writeSymlinkRule();
+    write(
+        "BUILD",
+        "load(':symlink.bzl', 'symlink')",
+        "symlink(",
+        "  name = 'foo-link',",
+        "  target = ':foo.txt'",
+        ")");
+    write("foo.txt", "foo");
+
+    buildTarget("//:foo-link");
+
+    assertOnlyOutputContent("//:foo-link", "foo-link", "foo" + lineSeparator());
+
+    // Delete link, re-plant symlink
+    getOutputPath("foo-link").delete();
+
+    buildTarget("//:foo-link");
+
+    assertOnlyOutputContent("//:foo-link", "foo-link", "foo" + lineSeparator());
+  }
+
   @Test
   public void downloadToplevel_symlinkTree() throws Exception {
     // TODO(chiwang): Make metadata for downloaded symlink non-remote.