# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1549319903 28800
# Node ID ba7eaff2647403b46204504dd317ecc8b79c6316
# Parent  01417ca7f2e2ca09911882b87a47ac83538f8cc2
check-py3-compat: manually format and print warnings

The warnings mechanism may print to stderr on Python 3. Independent buffering
of stdout and stderr can lead to warnings output not being printed properly.

This commit traps warnings when executing individual files and prints
warnings to stdout so output is deterministic.

Differential Revision: https://phab.mercurial-scm.org/D5845

diff -r 01417ca7f2e2 -r ba7eaff26474 contrib/check-py3-compat.py
--- a/contrib/check-py3-compat.py	Mon Feb 04 14:25:00 2019 -0800
+++ b/contrib/check-py3-compat.py	Mon Feb 04 14:38:23 2019 -0800
@@ -14,6 +14,7 @@
 import os
 import sys
 import traceback
+import warnings
 
 def check_compat_py2(f):
     """Check Python 3 compatibility for a file with Python 2"""
@@ -91,6 +92,11 @@
         fn = check_compat_py3
 
     for f in sys.argv[1:]:
-        fn(f)
+        with warnings.catch_warnings(record=True) as warns:
+            fn(f)
+
+        for w in warns:
+            print(warnings.formatwarning(w.message, w.category,
+                                         w.filename, w.lineno).rstrip())
 
     sys.exit(0)