bpo-32101: Add PYTHONDEVMODE environment variable (#4624)

* bpo-32101: Add sys.flags.dev_mode flag
  Rename also the "Developer mode" to the "Development mode".
* bpo-32101: Add PYTHONDEVMODE environment variable
  Mention it in the development chapiter.

3 files changed, 42 insertions, 9 deletions

diff --git a/Lib/asyncio/coroutines.py b/Lib/asyncio/coroutines.py
index b6f81a4..7d2ca05 100644
--- a/Lib/asyncio/coroutines.py
+++ b/Lib/asyncio/coroutines.py
@@ -27,11 +27,9 @@ def _is_debug_mode():
     # before you define your coroutines.  A downside of using this feature
     # is that tracebacks show entries for the CoroWrapper.__next__ method
     # when _DEBUG is true.
-    debug = (not sys.flags.ignore_environment and
-             bool(os.environ.get('PYTHONASYNCIODEBUG')))
-    if hasattr(sys, '_xoptions') and 'dev' in sys._xoptions:
-        debug = True
-    return debug
+    return (sys.flags.dev_mode
+            or (not sys.flags.ignore_environment
+                and bool(os.environ.get('PYTHONASYNCIODEBUG'))))
 
 
 _DEBUG = _is_debug_mode()
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index 96405e7..383302b 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -508,14 +508,18 @@ class CmdLineTest(unittest.TestCase):
             with self.subTest(envar_value=value):
                 assert_python_ok('-c', code, **env_vars)
 
-    def run_xdev(self, *args, check_exitcode=True):
+    def run_xdev(self, *args, check_exitcode=True, xdev=True):
         env = dict(os.environ)
         env.pop('PYTHONWARNINGS', None)
+        env.pop('PYTHONDEVMODE', None)
         # Force malloc() to disable the debug hooks which are enabled
         # by default for Python compiled in debug mode
         env['PYTHONMALLOC'] = 'malloc'
 
-        args = (sys.executable, '-X', 'dev', *args)
+        if xdev:
+            args = (sys.executable, '-X', 'dev', *args)
+        else:
+            args = (sys.executable, *args)
         proc = subprocess.run(args,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.STDOUT,
@@ -526,6 +530,14 @@ class CmdLineTest(unittest.TestCase):
         return proc.stdout.rstrip()
 
     def test_xdev(self):
+        # sys.flags.dev_mode
+        code = "import sys; print(sys.flags.dev_mode)"
+        out = self.run_xdev("-c", code, xdev=False)
+        self.assertEqual(out, "False")
+        out = self.run_xdev("-c", code)
+        self.assertEqual(out, "True")
+
+        # Warnings
         code = ("import sys, warnings; "
                 "print(' '.join('%s::%s' % (f[0], f[2].__name__) "
                                 "for f in warnings.filters))")
@@ -555,6 +567,7 @@ class CmdLineTest(unittest.TestCase):
                          "default::ResourceWarning "
                          "default::Warning")
 
+        # Memory allocator debug hooks
         try:
             import _testcapi
         except ImportError:
@@ -569,6 +582,7 @@ class CmdLineTest(unittest.TestCase):
                 alloc_name = "malloc_debug"
             self.assertEqual(out, alloc_name)
 
+        # Faulthandler
         try:
             import faulthandler
         except ImportError:
@@ -581,6 +595,7 @@ class CmdLineTest(unittest.TestCase):
     def check_pythonmalloc(self, env_var, name):
         code = 'import _testcapi; print(_testcapi.pymem_getallocatorsname())'
         env = dict(os.environ)
+        env.pop('PYTHONDEVMODE', None)
         if env_var is not None:
             env['PYTHONMALLOC'] = env_var
         else:
@@ -621,6 +636,24 @@ class CmdLineTest(unittest.TestCase):
             with self.subTest(env_var=env_var, name=name):
                 self.check_pythonmalloc(env_var, name)
 
+    def test_pythondevmode_env(self):
+        # Test the PYTHONDEVMODE environment variable
+        code = "import sys; print(sys.flags.dev_mode)"
+        env = dict(os.environ)
+        env.pop('PYTHONDEVMODE', None)
+        args = (sys.executable, '-c', code)
+
+        proc = subprocess.run(args, stdout=subprocess.PIPE,
+                              universal_newlines=True, env=env)
+        self.assertEqual(proc.stdout.rstrip(), 'False')
+        self.assertEqual(proc.returncode, 0, proc)
+
+        env['PYTHONDEVMODE'] = '1'
+        proc = subprocess.run(args, stdout=subprocess.PIPE,
+                              universal_newlines=True, env=env)
+        self.assertEqual(proc.stdout.rstrip(), 'True')
+        self.assertEqual(proc.returncode, 0, proc)
+
 
 class IgnoreEnvironmentTest(unittest.TestCase):
 
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 4b8fcb9..6346094 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -526,10 +526,12 @@ class SysModuleTest(unittest.TestCase):
         attrs = ("debug",
                  "inspect", "interactive", "optimize", "dont_write_bytecode",
                  "no_user_site", "no_site", "ignore_environment", "verbose",
-                 "bytes_warning", "quiet", "hash_randomization", "isolated")
+                 "bytes_warning", "quiet", "hash_randomization", "isolated",
+                 "dev_mode")
         for attr in attrs:
             self.assertTrue(hasattr(sys.flags, attr), attr)
-            self.assertEqual(type(getattr(sys.flags, attr)), int, attr)
+            attr_type = bool if attr == "dev_mode" else int
+            self.assertEqual(type(getattr(sys.flags, attr)), attr_type, attr)
         self.assertTrue(repr(sys.flags))
         self.assertEqual(len(sys.flags), len(attrs))