Address review comments

Author: fmeum

src/main/java/com/google/devtools/build/lib/bazel/BazelRepositoryModule.java

@@ -376,17 +376,29 @@ public void beforeCommand(CommandEnvironment env) throws AbruptExitException {
         repositoryCache.getRepoContentsCache().setPath(toPath(repoOptions.repoContentsCache, env));
       }
       Path repoContentsCachePath = repositoryCache.getRepoContentsCache().getPath();
-      if (repoContentsCachePath != null && env.getOutputBase().startsWith(repoContentsCachePath)) {
-        // This is dangerous as the repo contents cache GC may delete files in the output base.
-        throw new AbruptExitException(
-            detailedExitCode(
-                """
-                The repo contents cache [%s] is inside the output base [%s]. This can cause \
-                spurious failures. Disable the repo contents cache with `--repo_contents_cache=`, \
-                or specify `--repo_contents_cache=<path outside the output base>`.
-                """
-                    .formatted(repoContentsCachePath, env.getOutputBase()),
-                Code.BAD_REPO_CONTENTS_CACHE));
+      if (repoContentsCachePath != null) {
+        try {
+          Path resolvedRepoContentsCache = repoContentsCachePath.resolveSymbolicLinks();
+          Path resolvedOutputBase = env.getOutputBase().resolveSymbolicLinks();
+          if (resolvedOutputBase.startsWith(resolvedOutputBase)) {
+            // This is dangerous as the repo contents cache GC may delete files in the output base.
+            throw new AbruptExitException(
+                detailedExitCode(
+                    """
+                  The output base [%s] is inside the repo contents cache [%s]. This can cause \
+                  spurious failures. Disable the repo contents cache with `--repo_contents_cache=`, \
+                  or specify `--repo_contents_cache=<path that doesn't contain the output base>`.
+                  """
+                        .formatted(resolvedOutputBase, resolvedRepoContentsCache),
+                    Code.BAD_REPO_CONTENTS_CACHE));
+          }
+        } catch (IOException e) {
+          throw new AbruptExitException(
+              detailedExitCode(
+                  "could not resolve repo contents cache path: %s".formatted(e.getMessage()),
+                  Code.BAD_REPO_CONTENTS_CACHE),
+              e);
+        }
       }
       if (repoContentsCachePath != null
           && env.getWorkspace() != null

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

@@ -344,10 +344,20 @@ public void beforeCommand(CommandEnvironment env) throws AbruptExitException {
     boolean enableRemoteDownloader = shouldEnableRemoteDownloader(remoteOptions);
 
     if (enableDiskCache) {
-      if (env.getOutputBase().startsWith(remoteOptions.diskCache)) {
-        // This is dangerous as the disk cache GC may delete files in the output base.
+      try {
+        Path resolvedOutputBase = env.getOutputBase().resolveSymbolicLinks();
+        Path resolvedDiskCache =
+            env.getWorkingDirectory().getRelative(remoteOptions.diskCache).resolveSymbolicLinks();
+        if (resolvedOutputBase.startsWith(resolvedDiskCache)) {
+          // This is dangerous as the disk cache GC may delete files in the output base.
+          throw createOptionsExitException(
+              "The output base [%s] cannot be a subdirectory of the --disk_cache directory [%s]"
+                  .formatted(resolvedOutputBase, resolvedDiskCache),
+              FailureDetails.RemoteOptions.Code.EXECUTION_WITH_INVALID_CACHE);
+        }
+      } catch (IOException e) {
         throw createOptionsExitException(
-            "The --disk_cache directory cannot be a subdirectory of the output base",
+            "Failed to resolve disk cache directory: %s".formatted(e.getMessage()),
             FailureDetails.RemoteOptions.Code.EXECUTION_WITH_INVALID_CACHE);
       }
       var gcIdleTask =
@@ -1229,5 +1239,4 @@ static Credentials createCredentials(
   Downloader getRemoteDownloader() {
     return remoteDownloader;
   }
-
 }