From 5f6d3a0fd659d2cc1feacbae08a708858f1ce5ce Mon Sep 17 00:00:00 2001
From: "Erik M. Bray" <erik.bray@lri.fr>
Date: Fri, 10 Nov 2017 11:41:50 +0100
Subject: [PATCH] Fix legacy locale coercion tests on platforms that already
 have a default C.UTF-8 locale

---
 Lib/test/test_c_locale_coercion.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/Lib/test/test_c_locale_coercion.py b/Lib/test/test_c_locale_coercion.py
index 635c98faced9cd..5944e5f6b3e5be 100644
--- a/Lib/test/test_c_locale_coercion.py
+++ b/Lib/test/test_c_locale_coercion.py
@@ -160,11 +160,13 @@ def get_child_details(cls, env_vars):
 AVAILABLE_TARGETS = None
 CLI_COERCION_TARGET = None
 CLI_COERCION_WARNING = None
+DEFAULT_LC_CTYPE = None
 
 def setUpModule():
     global AVAILABLE_TARGETS
     global CLI_COERCION_TARGET
     global CLI_COERCION_WARNING
+    global DEFAULT_LC_CTYPE
 
     if AVAILABLE_TARGETS is not None:
         # initialization already done
@@ -181,6 +183,22 @@ def setUpModule():
         CLI_COERCION_TARGET = AVAILABLE_TARGETS[0]
         CLI_COERCION_WARNING = CLI_COERCION_WARNING_FMT.format(CLI_COERCION_TARGET)
 
+    # Determine the platform's default LC_CTYPE from the default locale.
+    # POSIX provides that there *exists* a default locale to provide when
+    # no environment variables are set, or are set to empty strings.  However,
+    # it does not specify that this default *must* be the "POSIX" locale, or
+    # how the platform selects the default.  In most cases it will be set to
+    # "C"/"POSIX" but this is not necessarily the case.
+    result, py_cmd = run_python_until_end(
+        "-c", "import locale; print(locale.setlocale(locale.LC_CTYPE))",
+        __isolated=True,
+        LANG="", LC_ALL="", LC_CTYPE="", PYTHONCOERCECLOCALE="0"
+    )
+    if not result.rc == 0:
+        result.fail(py_cmd)
+
+    DEFAULT_LC_CTYPE = result.out.decode("ascii").strip().upper()
+
 
 class _LocaleHandlingTestCase(unittest.TestCase):
     # Base class to check expected locale handling behaviour
@@ -301,6 +319,11 @@ def _check_c_locale_coercion(self,
                 # See https://bugs.python.org/issue30672 for discussion
                 if locale_to_set == "POSIX":
                     continue
+                elif locale_to_set == "" and DEFAULT_LC_CTYPE == "C.UTF-8":
+                    # The default locale is already C.UTF-8 so the subsequent tests
+                    # don't behave as expected (they assume the default LC_CTYPE will
+                    # be "C")
+                    continue
                 with self.subTest(env_var=env_var,
                                   nominal_locale=locale_to_set,
                                   PYTHONCOERCECLOCALE=coerce_c_locale):