[llvm] e5418e8 - [lit] Fix builtin diff importing system lit.util in subprocess mode (#206723)

[via llvm-commits]

Author: Prasoon Kumar
Date: 2026-06-30T13:13:33Z
New Revision: e5418e84fd8592c4dcaf412c064ac896aaa1f24c

URL: https://github.com/llvm/llvm-project/commit/e5418e84fd8592c4dcaf412c064ac896aaa1f24c
DIFF: https://github.com/llvm/llvm-project/commit/e5418e84fd8592c4dcaf412c064ac896aaa1f24c.diff

LOG: [lit] Fix builtin diff importing system lit.util in subprocess mode (#206723)

'import lit.util' silently picks up a system-installed lit package
instead of the local one, which may lack abs_path_preserve_drive.

Switch to 'from .. import util': in subprocess mode __package__ is None,
so the relative import raises ImportError and the fallback correctly
picks up the local util.py via PYTHONPATH

Signed-off-by: Prasoon Kumar <prasoonkumar054 at gmail.com>

Added: 
    

Modified: 
    llvm/utils/lit/lit/builtin_commands/diff.py

Removed: 
    


################################################################################
diff  --git a/llvm/utils/lit/lit/builtin_commands/
diff .py b/llvm/utils/lit/lit/builtin_commands/
diff .py
index 579a2649bc0af..9d1a398106664 100644
--- a/llvm/utils/lit/lit/builtin_commands/
diff .py
+++ b/llvm/utils/lit/lit/builtin_commands/
diff .py
@@ -7,18 +7,17 @@
 import sys
 
 # 
diff .py runs in two modes during the in-process migration:
-#   - In-process (default): imported as 'lit.builtin_commands.
diff ', so the
-#     'lit' package is already resolvable => lit.util works
-#   - Spawned fallback: run standalone via 'sys.executable 
diff .py', with
-#     PYTHONPATH set to the 'lit/' directory itself, not its parent. No entry
-#     on sys.path is the parent of 'lit/', so 'lit' can't be imported as package =>
-#     'lit.util' raises ImportError. util.py sits directly in that PYTHONPATH
-#     dir, so bare 'import util' resolves instead.
-# Both paths load the same module; the fallback handles the path 
diff erence.
-# TODO: Collapse to a standard 'import lit.util' once standalone spawning is removed.
+#   - In-process: imported as 'lit.builtin_commands.
diff ', so __package__ is
+#     set and the relative import resolves to lit.util from the source tree.
+#   - Spawned fallback: run as __main__ with __package__=None, so the relative
+#     import raises ImportError and the fallback picks up util.py via PYTHONPATH
+#     pointing at the lit/ directory.
+# A relative import is used (not 'import lit.util') to avoid accidentally
+# importing a system-installed lit package that may lack abs_path_preserve_drive.
+# TODO: Collapse to 'from .. import util' once standalone spawning is removed.
 
 try:
-    import lit.util as util
+    from .. import util
 except ImportError:
     import util