Add utility for parsing shebangs and resolving PATH

pre_commit/commands/install_uninstall.py

@@ -5,10 +5,10 @@ import io
 import logging
 import os
 import os.path
-import stat
 import sys
 
 from pre_commit.logging_handler import LoggingHandler
+from pre_commit.util import make_executable
 from pre_commit.util import mkdirp
 from pre_commit.util import resource_filename
 
@@ -42,14 +42,6 @@ def is_previous_pre_commit(filename):
     return any(hash in contents for hash in PREVIOUS_IDENTIFYING_HASHES)
 
 
-def make_executable(filename):
-    original_mode = os.stat(filename).st_mode
-    os.chmod(
-        filename,
-        original_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH,
-    )
-
-
 def install(runner, overwrite=False, hooks=False, hook_type='pre-commit'):
     """Install the pre-commit hooks."""
     hook_path = runner.get_hook_path(hook_type)

pre_commit/parse_shebang.py

@@ -0,0 +1,95 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import io
+import os.path
+import shlex
+import string
+
+from pre_commit import five
+
+
+printable = frozenset(string.printable)
+
+
+def parse_bytesio(bytesio):
+    """Parse the shebang from a file opened for reading binary."""
+    if bytesio.read(2) != b'#!':
+        return ()
+    first_line = bytesio.readline()
+    try:
+        first_line = first_line.decode('US-ASCII')
+    except UnicodeDecodeError:
+        return ()
+
+    # Require only printable ascii
+    for c in first_line:
+        if c not in printable:
+            return ()
+
+    # shlex.split is horribly broken in py26 on text strings
+    cmd = tuple(shlex.split(five.n(first_line)))
+    if cmd[0] == '/usr/bin/env':
+        cmd = cmd[1:]
+    return cmd
+
+
+def parse_filename(filename):
+    """Parse the shebang given a filename."""
+    if not os.path.exists(filename) or not os.access(filename, os.X_OK):
+        return ()
+
+    with io.open(filename, 'rb') as f:
+        return parse_bytesio(f)
+
+
+def find_executable(exe, _environ=None):
+    exe = os.path.normpath(exe)
+    if os.sep in exe:
+        return exe
+
+    environ = _environ if _environ is not None else os.environ
+
+    if 'PATHEXT' in environ:
+        possible_exe_names = (exe,) + tuple(
+            exe + ext.lower() for ext in environ['PATHEXT'].split(os.pathsep)
+        )
+    else:
+        possible_exe_names = (exe,)
+
+    for path in environ.get('PATH', '').split(os.pathsep):
+        for possible_exe_name in possible_exe_names:
+            joined = os.path.join(path, possible_exe_name)
+            if os.path.isfile(joined) and os.access(joined, os.X_OK):
+                return joined
+    else:
+        return None
+
+
+def normexe(orig_exe):
+    if os.sep not in orig_exe:
+        exe = find_executable(orig_exe)
+        if exe is None:
+            raise OSError('Executable {0} not found'.format(orig_exe))
+        return exe
+    else:
+        return orig_exe
+
+
+def normalize_cmd(cmd):
+    """Fixes for the following issues on windows
+    - http://bugs.python.org/issue8557
+    - windows does not parse shebangs
+
+    This function also makes deep-path shebangs work just fine
+    """
+    # Use PATH to determine the executable
+    exe = normexe(cmd[0])
+
+    # Figure out the shebang from the resulting command
+    cmd = parse_filename(exe) + (exe,) + cmd[1:]
+
+    # This could have given us back another bare executable
+    exe = normexe(cmd[0])
+
+    return (exe,) + cmd[1:]

pre_commit/util.py

@@ -14,6 +14,7 @@ import tempfile
 import pkg_resources
 
 from pre_commit import five
+from pre_commit import parse_shebang
 
 
 @contextlib.contextmanager
@@ -110,6 +111,14 @@ def resource_filename(filename):
     )
 
 
+def make_executable(filename):
+    original_mode = os.stat(filename).st_mode
+    os.chmod(
+        filename,
+        original_mode | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH,
+    )
+
+
 class CalledProcessError(RuntimeError):
     def __init__(self, returncode, cmd, expected_returncode, output=None):
         super(CalledProcessError, self).__init__(
@@ -166,12 +175,14 @@ def cmd_output(*cmd, **kwargs):
     }
 
     # py2/py3 on windows are more strict about the types here
-    cmd = [five.n(arg) for arg in cmd]
+    cmd = tuple(five.n(arg) for arg in cmd)
     kwargs['env'] = dict(
         (five.n(key), five.n(value))
         for key, value in kwargs.pop('env', {}).items()
     ) or None
 
+    cmd = parse_shebang.normalize_cmd(cmd)
+
     popen_kwargs.update(kwargs)
     proc = __popen(cmd, **popen_kwargs)
     stdout, stderr = proc.communicate()