bpo-34530: Fix distutils find_executable()

Lib/distutils/spawn.py

@@ -6,8 +6,9 @@
 executable name.
 """
 
-import sys
 import os
+import shutil
+import sys
 
 from distutils.errors import DistutilsPlatformError, DistutilsExecError
 from distutils.debug import DEBUG
@@ -172,21 +173,4 @@ def find_executable(executable, path=None):
     A string listing directories separated by 'os.pathsep'; defaults to
     os.environ['PATH'].  Returns the complete filename or None if not found.
     """
-    if path is None:
-        path = os.environ['PATH']
-
-    paths = path.split(os.pathsep)
-    base, ext = os.path.splitext(executable)
-
-    if (sys.platform == 'win32') and (ext != '.exe'):
-        executable = executable + '.exe'
-
-    if not os.path.isfile(executable):
-        for p in paths:
-            f = os.path.join(p, executable)
-            if os.path.isfile(f):
-                # the file exists, we have a shot at spawn working
-                return f
-        return None
-    else:
-        return executable
+    return shutil.which(executable, path=path)

Lib/distutils/tests/test_spawn.py

@@ -1,9 +1,11 @@
 """Tests for distutils.spawn."""
-import unittest
-import sys
 import os
-from test.support import run_unittest, unix_shell
+import stat
+import sys
+import unittest
+from test.support import run_unittest, unix_shell, temp_dir
 
+from distutils.spawn import find_executable
 from distutils.spawn import _nt_quote_args
 from distutils.spawn import spawn
 from distutils.errors import DistutilsExecError
@@ -51,6 +53,21 @@ def test_spawn(self):
         os.chmod(exe, 0o777)
         spawn([exe])  # should work without any error
 
+    def test_find_executable(self):
+        with temp_dir() as tmp_dir:
+            # Give the temporary program an ".exe" suffix for all.
+            # It's needed on Windows and not harmful on other platforms.
+            program = "testprogram" + ".exe"
+
+            filename = os.path.join(tmp_dir, program)
+            with open(filename, "wb"):
+                pass
+            os.chmod(filename, stat.S_IXUSR)
+
+            rv = find_executable(program, path=tmp_dir)
+            self.assertEqual(rv, filename)
+
+
 def test_suite():
     return unittest.makeSuite(SpawnTestCase)
 

Misc/NEWS.d/next/Library/2018-08-28-14-48-44.bpo-34530.ZZjx45.rst

@@ -0,0 +1,4 @@
+distutils.spawn.find_executable() has been reimplemented using
+shutil.which() to fix two issues: fallback on os.defpath if the PATH
+environment variable is not set, and respect the PATHEXT environment
+variable on Windows.