Remote: Don't delete downloaded files for remote build without bytes.

Before this change, when remote build without bytes is enabled, intermediate outputs which are also inputs to local actions will be downloaded for local execution. After build finished, these downloaded files are deleted to keep Bazel's view of the output base identical with the output base i.e. files that Bazel thinks exist only remotely actually do. However, these intermediate outputs maybe used later in which case Bazel need to download them again which is a performance issue. bazelbuild#12855

This change fix the issue by removing the code used to delete downloaded files. Bazel should be able to take the local file as the source of truth if it exists (otherwise, it is a bug).

This is also an essential step to implement separation of downloads. bazelbuild#12665

PiperOrigin-RevId: 363131672

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

@@ -747,14 +747,6 @@ public void afterCommand() throws AbruptExitException {
       logger.atWarning().withCause(e).log(failureMessage);
     }
 
-    try {
-      deleteDownloadedInputs();
-    } catch (IOException e) {
-      failure = e;
-      failureCode = Code.DOWNLOADED_INPUTS_DELETION_FAILURE;
-      failureMessage = "Failed to delete downloaded inputs";
-    }
-
     buildEventArtifactUploaderFactoryDelegate.reset();
     repositoryRemoteExecutorFactoryDelegate.reset();
     remoteDownloaderSupplier.set(null);
@@ -768,30 +760,6 @@ public void afterCommand() throws AbruptExitException {
     }
   }
 
-  /**
-   * Delete any input files that have been fetched from the remote cache during the build. This is
-   * so that Bazel's view of the output base is identical with the output base after a build i.e.
-   * files that Bazel thinks exist only remotely actually do.
-   */
-  private void deleteDownloadedInputs() throws IOException {
-    if (actionInputFetcher == null) {
-      return;
-    }
-    IOException deletionFailure = null;
-    for (Path file : actionInputFetcher.downloadedFiles()) {
-      try {
-        file.delete();
-      } catch (IOException e) {
-        logger.atSevere().withCause(e).log(
-            "Failed to delete remote output '%s' from the output base.", file);
-        deletionFailure = e;
-      }
-    }
-    if (deletionFailure != null) {
-      throw deletionFailure;
-    }
-  }
-
   private void closeRpcLogFile() throws IOException {
     if (rpcLogFile != null) {
       AsynchronousFileOutputStream oldLogFile = rpcLogFile;

src/test/shell/bazel/remote/remote_execution_test.sh

@@ -1011,8 +1011,8 @@ EOF
   [[ $(< ${localtxt}) == "remotelocal" ]] \
   || fail "Unexpected contents in " ${localtxt} ": " $(< ${localtxt})
 
-  (! [[ -f bazel-bin/a/remote.txt ]]) \
-  || fail "Expected bazel-bin/a/remote.txt to have been deleted again"
+  [[ -f bazel-bin/a/remote.txt ]] \
+  || fail "Expected bazel-bin/a/remote.txt to be downloaded"
 }
 
 function test_download_outputs_invalidation() {
@@ -1105,8 +1105,8 @@ EOF
   [[ $(< ${outtxt}) == "Hello buchgr!" ]] \
   || fail "Unexpected contents in "${outtxt}":" $(< ${outtxt})
 
-  (! [[ -f bazel-bin/a/template.txt ]]) \
-  || fail "Expected bazel-bin/a/template.txt to have been deleted again"
+  [[ -f bazel-bin/a/template.txt ]] \
+  || fail "Expected bazel-bin/a/template.txt to be downloaded"
 }
 
 function test_downloads_toplevel() {