xargs returns nonzero for negate + not found exe (fixes pcre + not found #447)

pre_commit/languages/pcre.py

@@ -1,11 +1,12 @@
 from __future__ import unicode_literals
 
-from sys import platform
+import sys
 
 from pre_commit.xargs import xargs
 
 
 ENVIRONMENT_DIR = None
+GREP = 'ggrep' if sys.platform == 'darwin' else 'grep'
 
 
 def install_environment(
@@ -19,10 +20,7 @@ def install_environment(
 
 def run_hook(repo_cmd_runner, hook, file_args):
     # For PCRE the entry is the regular expression to match
-    cmd = (
-        'ggrep' if platform == 'darwin' else 'grep',
-        '-H', '-n', '-P',
-    ) + tuple(hook['args']) + (hook['entry'],)
+    cmd = (GREP, '-H', '-n', '-P') + tuple(hook['args']) + (hook['entry'],)
 
     # Grep usually returns 0 for matches, and nonzero for non-matches so we
     # negate it here.

pre_commit/parse_shebang.py

@@ -11,7 +11,8 @@ printable = frozenset(string.printable)
 
 
 class ExecutableNotFoundError(OSError):
-    pass
+    def to_output(self):
+        return (1, self.args[0].encode('UTF-8'), b'')
 
 
 def parse_bytesio(bytesio):

pre_commit/util.py

@@ -172,16 +172,16 @@ def cmd_output(*cmd, **kwargs):
     try:
         cmd = parse_shebang.normalize_cmd(cmd)
     except parse_shebang.ExecutableNotFoundError as e:
-        returncode, stdout, stderr = (-1, e.args[0].encode('UTF-8'), b'')
+        returncode, stdout, stderr = e.to_output()
     else:
         popen_kwargs.update(kwargs)
         proc = __popen(cmd, **popen_kwargs)
         stdout, stderr = proc.communicate()
-        if encoding is not None and stdout is not None:
-            stdout = stdout.decode(encoding)
-        if encoding is not None and stderr is not None:
-            stderr = stderr.decode(encoding)
         returncode = proc.returncode
+    if encoding is not None and stdout is not None:
+        stdout = stdout.decode(encoding)
+    if encoding is not None and stderr is not None:
+        stderr = stderr.decode(encoding)
 
     if retcode is not None and retcode != returncode:
         raise CalledProcessError(

pre_commit/xargs.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
+from pre_commit import parse_shebang
 from pre_commit.util import cmd_output
 
 
@@ -52,6 +53,11 @@ def xargs(cmd, varargs, **kwargs):
     stdout = b''
     stderr = b''
 
+    try:
+        parse_shebang.normexe(cmd[0])
+    except parse_shebang.ExecutableNotFoundError as e:
+        return e.to_output()
+
     for run_cmd in partition(cmd, varargs, **kwargs):
         proc_retcode, proc_out, proc_err = cmd_output(
             *run_cmd, encoding=None, retcode=None