Implement 'negate' to simplify pcre

tests/util_test.py

@@ -9,7 +9,6 @@ import pytest
 from pre_commit.util import clean_path_on_failure
 from pre_commit.util import cwd
 from pre_commit.util import memoize_by_cwd
-from pre_commit.util import shell_escape
 from pre_commit.util import tmpdir
 
 
@@ -79,18 +78,6 @@ def test_clean_path_on_failure_cleans_for_system_exit(in_tmpdir):
     assert not os.path.exists('foo')
 
 
-@pytest.mark.parametrize(
-    ('input_str', 'expected'),
-    (
-        ('', "''"),
-        ('foo"bar', "'foo\"bar'"),
-        ("foo'bar", "'foo'\"'\"'bar'")
-    ),
-)
-def test_shell_escape(input_str, expected):
-    assert shell_escape(input_str) == expected
-
-
 def test_tmpdir():
     with tmpdir() as tempdir:
         assert os.path.exists(tempdir)

tests/xargs_test.py

@@ -45,3 +45,28 @@ def test_xargs_smoke():
     assert ret == 0
     assert out == b'hello world\n'
     assert err == b''
+
+
+exit_cmd = ('bash', '-c', 'exit $1', '--')
+# Abuse max_length to control the exit code
+max_length = len(' '.join(exit_cmd)) + 2
+
+
+def test_xargs_negate():
+    ret, _, _ = xargs.xargs(
+        exit_cmd, ('1',), negate=True, _max_length=max_length,
+    )
+    assert ret == 0
+
+    ret, _, _ = xargs.xargs(
+        exit_cmd, ('1', '0'), negate=True, _max_length=max_length,
+    )
+    assert ret == 1
+
+
+def test_xargs_retcode_normal():
+    ret, _, _ = xargs.xargs(exit_cmd, ('0',), _max_length=max_length)
+    assert ret == 0
+
+    ret, _, _ = xargs.xargs(exit_cmd, ('0', '1'), _max_length=max_length)
+    assert ret == 1