Fix blatant bug with Skyframe globbing where we incorrectly allow dangling symlinks to match a glob pattern.

This bug has/had two consequences:

(1) Change pruning will incorrectly cut off changes to GlobValues that ought to now match more files (say, if a dangling symlink comes into existence), causing a package to be incorrectly incrementally not re-loaded.

(2) After a recent change to PackageFunction where we use a fancy hybrid globbing approach, we use skyframe globbing on incremental package loading. So if a re-loaded package has the same glob pattern but this glob pattern incorrectly matches a dangling symlink, the re-loaded package will incorrectly have a target for the dangling symlink path.

--
MOS_MIGRATED_REVID=115274842

1 files changed, 3 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/GlobFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/GlobFunction.java
index 50b7c294c7..e1c877f455 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/GlobFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/GlobFunction.java
@@ -146,6 +146,9 @@ public final class GlobFunction implements SkyFunction {
                 "readdir and stat disagree about whether " + symlinkRootedPath.asPath()
                     + " is a symlink."), Transience.TRANSIENT);
           }
+          if (!symlinkFileValue.exists()) {
+            continue;
+          }
           isDirectory = symlinkFileValue.isDirectory();
         }