[CI] Add debug logging for premerge advisor explanations

premerge/advisor/advisor_lib.py

@@ -3,6 +3,8 @@
 import sqlite3
 import logging
 import re
+import json
+import os
 
 import git_utils
 
@@ -200,17 +202,50 @@ def _try_explain_flaky_failure(
     return None
 
 
+def _log_explanation_request(
+    explanation_request: TestExplanationRequest,
+    base_commit_index: int,
+    db_connection: sqlite3.Connection,
+    explanations: list[FailureExplanation],
+    debug_folder: str,
+):
+    explanation_log = {
+        "request": explanation_request,
+        "explanations": explanations,
+        "base_commit_index": base_commit_index,
+        "relevant_previous_failures": [],
+    }
+    for failure in explanation_request["failures"]:
+        test_name_matches = db_connection.execute(
+            "SELECT failure_message, commit_index, test_file "
+            "FROM failures WHERE source_type='postcommit' AND platform=? AND test_file=?",
+            (
+                explanation_request["platform"],
+                failure["name"],
+            ),
+        ).fetchall()
+        explanation_log["relevant_previous_failures"].extend(test_name_matches)
+    with open(
+        os.path.join(
+            debug_folder, str(base_commit_index) + "-" + str(int(time.time())) + ".txt"
+        ),
+        "w",
+    ) as output_file:
+        json.dump(explanation_log, output_file)
+
+
 def explain_failures(
     explanation_request: TestExplanationRequest,
     repository_path: str,
     db_connection: sqlite3.Connection,
+    debug_folder: str | None = None,
 ) -> list[FailureExplanation]:
     _canonicalize_failures(explanation_request["failures"])
     explanations = []
+    commit_index = git_utils.get_commit_index(
+        explanation_request["base_commit_sha"], repository_path, db_connection
+    )
     for test_failure in explanation_request["failures"]:
-        commit_index = git_utils.get_commit_index(
-            explanation_request["base_commit_sha"], repository_path, db_connection
-        )
         # We want to try and explain flaky failures first. Otherwise we might
         # explain a flaky failure as a failure at head if there is a recent
         # failure in the last couple of commits.
@@ -235,6 +270,10 @@ def explain_failures(
         explanations.append(
             {"name": test_failure["name"], "explained": False, "reason": None}
         )
+    if debug_folder:
+        _log_explanation_request(
+            explanation_request, commit_index, db_connection, explanations, debug_folder
+        )
     return explanations
 
 

premerge/advisor/advisor_lib_test.py

@@ -1,6 +1,7 @@
 import unittest
 import tempfile
 import sqlite3
+import json
 import os
 
 import advisor_lib
@@ -165,6 +166,7 @@ def _get_explained_failures(
         prev_failure_failure_name="a.ll",
         prev_failure_failure_message="failed in way 1",
         prev_failure_platform="linux-x86_64",
+        debug_folder=None,
     ) -> list[advisor_lib.FailureExplanation]:
         """Constructs explanations.
 
@@ -192,7 +194,7 @@ def _get_explained_failures(
             "platform": platform,
         }
         return advisor_lib.explain_failures(
-            explanation_request, self.repository_path, self.db_connection
+            explanation_request, self.repository_path, self.db_connection, debug_folder
         )
 
     # Test that we can explain away a failure at head, assuming all of the
@@ -313,6 +315,35 @@ def test_no_explain_different_test_file(self):
             ],
         )
 
+    def test_explain_failures_debug_logging(self):
+        with tempfile.TemporaryDirectory() as debug_folder:
+            self._get_explained_failures(debug_folder=debug_folder)
+            debug_outputs = os.listdir(debug_folder)
+            self.assertEqual(len(debug_outputs), 1)
+            with open(os.path.join(debug_folder, debug_outputs[0])) as debug_file:
+                explanation_log = json.load(debug_file)
+                self.assertDictEqual(
+                    explanation_log,
+                    {
+                        "request": {
+                            "failures": [
+                                {"name": "a.ll", "message": "failed in way 1"}
+                            ],
+                            "base_commit_sha": "8d29a3bb6f3d92d65bf5811b53bf42bf63685359",
+                            "platform": "linux-x86_64",
+                        },
+                        "explanations": [
+                            {
+                                "name": "a.ll",
+                                "explained": True,
+                                "reason": "This test is already failing at the base commit.",
+                            }
+                        ],
+                        "base_commit_index": 1,
+                        "relevant_previous_failures": [["failed in way 1", 1, "a.ll"]],
+                    },
+                )
+
     def _setup_flaky_test_info(
         self,
         source_type="postcommit",