[8.0.0] Fix permissions on directories while incrementally updating a…

… symlink tree. (#24292)

Compare with EnsureDirReadAndWritePerms in build-runfiles.cc.

PiperOrigin-RevId: 695254434
Change-Id: If8694ad4fdd666739419ca02373a35a2cf36f4ac

src/main/java/com/google/devtools/build/lib/exec/SymlinkTreeHelper.java

@@ -281,13 +281,15 @@ void syncTreeRecursively(Path at) throws IOException {
       } else if (!stat.isDirectory()) {
         at.deleteTree();
         at.createDirectoryAndParents();
+      } else {
+        // If the directory already exists, ensure it has appropriate permissions.
+        int perms = stat.getPermissions();
+        if (perms == -1) {
+          at.chmod(0755);
+        } else if ((perms & 0700) != 0700) {
+          at.chmod(stat.getPermissions() | 0700);
+        }
       }
-      // TODO(ulfjack): provide the mode bits from FileStatus and use that to construct the correct
-      //  chmod call here. Note that we do not have any tests for this right now. Something like
-      //  this:
-      // if (!stat.isExecutable() || !stat.isReadable()) {
-      //   at.chmod(stat.getMods() | 0700);
-      // }
       for (Dirent dirent : at.readdir(Symlinks.NOFOLLOW)) {
         String basename = dirent.getName();
         Path next = at.getChild(basename);

src/test/java/com/google/devtools/build/lib/exec/SymlinkTreeHelperTest.java

@@ -153,6 +153,7 @@ public void createSymlinksDirectly(@TestParameter boolean replace) throws Except
       treeFile.createDirectoryAndParents();
       treeSymlink.createDirectoryAndParents();
       treeMissing.createDirectoryAndParents();
+      treeWorkspace.chmod(000);
     }
 
     helper.createSymlinksDirectly(symlinkMap);