[CI] Allow Explaining Failures Where LLVM Root Dir Differs

The postsubmit and premerge CI setups build LLVM inside different
directories due to how Github Actions sets things up. Use a regex to
eliminate the differences so we can explain away failures that only
differ due to the path. Most test cases seem to have the file path
printed in the failure message.

Reviewers: dschuff, lnihlen, cmtice, dwblaikie, gburgessiv, Keenuts

Reviewed By: Keenuts, dwblaikie

Pull Request: #645

Author: boomanaiden154

premerge/advisor/advisor_lib.py

@@ -2,6 +2,8 @@
 import time
 import sqlite3
 import logging
+import re
+
 import git_utils
 
 
@@ -70,9 +72,17 @@ def setup_db(db_path: str) -> sqlite3.Connection:
     return connection
 
 
+def _canonicalize_failures(failures: list[TestFailure]):
+    for failure in failures:
+        failure["message"] = re.sub(
+            r"\/home\/.*\/llvm-project", "llvm-project", failure["message"]
+        )
+
+
 def upload_failures(
     failure_info: FailureUpload, db_connection: sqlite3.Connection, repository_path: str
 ):
+    _canonicalize_failures(failure_info["failures"])
     failures = []
     for failure in failure_info["failures"]:
         failures.append(
@@ -181,6 +191,7 @@ def explain_failures(
     repository_path: str,
     db_connection: sqlite3.Connection,
 ) -> list[FailureExplanation]:
+    _canonicalize_failures(explanation_request["failures"])
     explanations = []
     for test_failure in explanation_request["failures"]:
         commit_index = git_utils.get_commit_index(

premerge/advisor/advisor_lib_test.py

@@ -242,6 +242,23 @@ def test_explain_head_within_range(self):
             ],
         )
 
+    # Test that we can explain test failures where the llvm-project root is
+    # located in a different path.
+    def test_explain_different_root_path(self):
+        self.assertListEqual(
+            self._get_explained_failures(
+                failure_message="/home/_w/llvm-project/test1/test1.ll failed",
+                prev_failure_failure_message="/home/gha/llvm-project/test1/test1.ll failed",
+            ),
+            [
+                {
+                    "name": "a.ll",
+                    "explained": True,
+                    "reason": "This test is already failing at the base commit.",
+                }
+            ],
+        )
+
     # Test that we do not explain away a failure at head if the only matching
     # failure information comes from a PR.
     def test_no_explain_different_source_type(self):