Improve not found error with script paths (./exe)

pre_commit/parse_shebang.py

@@ -42,16 +42,21 @@ def find_executable(exe, _environ=None):
         return None
 
 
-def normexe(orig_exe):
-    if os.sep not in orig_exe:
-        exe = find_executable(orig_exe)
+def normexe(orig):
+    def _error(msg):
+        raise ExecutableNotFoundError('Executable `{}` {}'.format(orig, msg))
+
+    if os.sep not in orig and (not os.altsep or os.altsep not in orig):
+        exe = find_executable(orig)
         if exe is None:
-            raise ExecutableNotFoundError(
-                'Executable `{}` not found'.format(orig_exe),
-            )
+            _error('not found')
         return exe
+    elif not os.access(orig, os.X_OK):
+        _error('not found')
+    elif os.path.isdir(orig):
+        _error('is a directory')
     else:
-        return orig_exe
+        return orig
 
 
 def normalize_cmd(cmd):

tests/parse_shebang_test.py

@@ -85,6 +85,22 @@ def test_normexe_does_not_exist():
     assert excinfo.value.args == ('Executable `i-dont-exist-lol` not found',)
 
 
+def test_normexe_does_not_exist_sep():
+    with pytest.raises(OSError) as excinfo:
+        parse_shebang.normexe('./i-dont-exist-lol')
+    assert excinfo.value.args == ('Executable `./i-dont-exist-lol` not found',)
+
+
+def test_normexe_is_a_directory(tmpdir):
+    with tmpdir.as_cwd():
+        tmpdir.join('exe').ensure_dir()
+        exe = os.path.join('.', 'exe')
+        with pytest.raises(OSError) as excinfo:
+            parse_shebang.normexe(exe)
+        msg, = excinfo.value.args
+        assert msg == 'Executable `{}` is a directory'.format(exe)
+
+
 def test_normexe_already_full_path():
     assert parse_shebang.normexe(sys.executable) == sys.executable
 
@@ -107,14 +123,14 @@ def test_normalize_cmd_PATH():
 
 
 def test_normalize_cmd_shebang(in_tmpdir):
-    python = distutils.spawn.find_executable('python')
-    path = write_executable(python.replace(os.sep, '/'))
+    python = distutils.spawn.find_executable('python').replace(os.sep, '/')
+    path = write_executable(python)
     assert parse_shebang.normalize_cmd((path,)) == (python, path)
 
 
 def test_normalize_cmd_PATH_shebang_full_path(in_tmpdir):
-    python = distutils.spawn.find_executable('python')
-    path = write_executable(python.replace(os.sep, '/'))
+    python = distutils.spawn.find_executable('python').replace(os.sep, '/')
+    path = write_executable(python)
     with bin_on_path():
         ret = parse_shebang.normalize_cmd(('run',))
         assert ret == (python, os.path.abspath(path))