From ed57f02bd671e9102cb58b621a21134b7a1115e9 Mon Sep 17 00:00:00 2001
From: Alex Szabo <alex.szabo@elastic.co>
Date: Thu, 1 Feb 2024 10:43:24 +0100
Subject: [PATCH] [Ops] Add debug logging to certain jest error cases (#175988)

## Summary
We see quite frequently this kind of error in Jest unit tests:
```
Error: The `document` global was defined when React was initialized, but is not defined anymore. This can happen in a test environment if a component schedules an update from an asynchronous callback, but the test has already finished running. To solve this, you can either unmount the component at the end of your test (and ensure that any asynchronous operations get canceled in `componentWillUnmount`), or you can change the test itself to be asynchronous.
```

As the test execution stops due to this runtime error, and the console
logging is disabled in CI, we don't see a lot of the context of the
error.

This PR adds minimal extra logging when the case of this error happens.
---
 packages/kbn-test/jest-preset.js              |  3 ++
 .../logging_result_processor.js               | 36 +++++++++++++++++++
 2 files changed, 39 insertions(+)
 create mode 100644 packages/kbn-test/src/jest/result_processors/logging_result_processor.js

diff --git a/packages/kbn-test/jest-preset.js b/packages/kbn-test/jest-preset.js
index d3795c775ea21..df9ed4cab4f51 100644
--- a/packages/kbn-test/jest-preset.js
+++ b/packages/kbn-test/jest-preset.js
@@ -130,4 +130,7 @@ module.exports = {
   globals: {
     structuredClone: {},
   },
+
+  testResultsProcessor:
+    '<rootDir>/packages/kbn-test/src/jest/result_processors/logging_result_processor.js',
 };
diff --git a/packages/kbn-test/src/jest/result_processors/logging_result_processor.js b/packages/kbn-test/src/jest/result_processors/logging_result_processor.js
new file mode 100644
index 0000000000000..b9b00dc8ee765
--- /dev/null
+++ b/packages/kbn-test/src/jest/result_processors/logging_result_processor.js
@@ -0,0 +1,36 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+const FAILURE_MESSAGE_TRIGGERS = ['but is not defined anymore'];
+const log = (...args) => {
+  const loggable = args.map((arg) =>
+    typeof arg === 'string' ? arg : JSON.stringify(arg, null, 2)
+  );
+  process.stdout.write(`${loggable.join(' ')}\n`, 'utf8');
+};
+/**
+ * This processor looks for specific errors, and logs the result context of test suites where they occur.
+ * @param results
+ * @returns {*}
+ */
+module.exports = (results) => {
+  const resultsThatMatchTriggers = results.testResults.filter(
+    (e) =>
+      e.failureMessage &&
+      FAILURE_MESSAGE_TRIGGERS.some((trigger) => e.failureMessage.includes(trigger))
+  );
+
+  if (resultsThatMatchTriggers.length !== 0) {
+    log('The following test suites failed, with notable errors:');
+    resultsThatMatchTriggers.forEach((e) => {
+      log(` -> ${e.testFilePath}`, 'Details: ', e, '\n');
+    });
+  }
+
+  return results;
+};