From 26644cb2b7e7a1329ae4befed3b1bb46e9a743d1 Mon Sep 17 00:00:00 2001
From: David Foster <david@dafoster.net>
Date: Sun, 7 Jan 2024 17:31:04 -0500
Subject: [PATCH] Continuous Integration: Export warnings as warning
 annotations in GitHub Actions

---
 src/crystal/tests/index.py | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/crystal/tests/index.py b/src/crystal/tests/index.py
index f251be0d..e8f785a0 100644
--- a/src/crystal/tests/index.py
+++ b/src/crystal/tests/index.py
@@ -1,3 +1,4 @@
+from contextlib import contextmanager
 from crystal.tests import (
     test_addgroup,
     test_addrooturl,
@@ -34,7 +35,7 @@
 import sys
 import time
 import traceback
-from typing import Any, Callable, Coroutine, Dict, List, Optional, Tuple
+from typing import Any, Callable, Coroutine, Dict, List, Iterator, Optional, Tuple
 from unittest import SkipTest
 import warnings
 
@@ -232,3 +233,27 @@ def _run_tests(test_names: List[str]) -> bool:
         print()
     
     return is_ok
+
+
+@contextmanager
+def _warnings_sent_to_ci() -> Iterator[None]:
+    if not _running_in_ci():
+        yield
+        return
+    
+    super_showwarning = warnings.showwarning  # capture
+    
+    def showwarning(message, category, filename, lineno, file=None, line=None):
+        # Syntax: https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-setting-a-warning-message
+        print(f'::warning file={filename},line={lineno}::{message}')
+        return super_showwarning(message, category, filename, lineno, file, line)
+    
+    warnings.showwarning = showwarning
+    try:
+        yield
+    finally:
+        warnings.showwarning = super_showwarning
+
+
+def _running_in_ci() -> bool:
+    return os.environ.get('GITHUB_ACTIONS') == 'true'