From 8a8aaf5a6006cbd8d7957eece08c88c33b2e442e Mon Sep 17 00:00:00 2001
From: Anthony Sottile <asottile@umich.edu>
Date: Tue, 4 Aug 2015 13:45:41 -0700
Subject: [PATCH] Add a hook to verify python ast.

---
 README.md                     |  1 +
 hooks.yaml                    |  6 ++++++
 pre_commit_hooks/check_ast.py | 36 +++++++++++++++++++++++++++++++++++
 setup.py                      |  1 +
 tests/check_ast_test.py       | 15 +++++++++++++++
 5 files changed, 59 insertions(+)
 create mode 100644 pre_commit_hooks/check_ast.py
 create mode 100644 tests/check_ast_test.py

diff --git a/README.md b/README.md
index 93b6360..65e8617 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,7 @@ Add this to your `.pre-commit-config.yaml`
       see `.pre-commit-config.yaml` in this repository for an example.
 - `check-added-large-files` - Prevent giant files from being committed.
     - Specify what is "too large" with `args: ['--maxkb=123']` (default=500kB).
+- `check-ast` - Simply check whether files parse as valid python.
 - `check-case-conflict` - Check for files with names that would conflict on a
   case-insensitive filesystem like MacOS HFS+ or Windows FAT.
 - `check-docstring-first` - Checks for a common error of placing code before
diff --git a/hooks.yaml b/hooks.yaml
index 9282867..8fcbe78 100644
--- a/hooks.yaml
+++ b/hooks.yaml
@@ -12,6 +12,12 @@
     language: python
     # Match all files
     files: ''
+-   id: check-ast
+    name: Check python ast
+    description: Simply check whether the files parse as valid python.
+    entry: check-ast
+    language: python
+    files: '\.py$'
 -   id: check-case-conflict
     name: Check for case conflicts
     description: Check for files that would conflict in case-insensitive filesystems
diff --git a/pre_commit_hooks/check_ast.py b/pre_commit_hooks/check_ast.py
new file mode 100644
index 0000000..c993e6a
--- /dev/null
+++ b/pre_commit_hooks/check_ast.py
@@ -0,0 +1,36 @@
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import argparse
+import ast
+import os.path
+import sys
+import traceback
+
+
+def check_ast(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*')
+    args = parser.parse_args(argv)
+
+    _, interpreter = os.path.split(sys.executable)
+
+    retval = 0
+    for filename in args.filenames:
+
+        try:
+            ast.parse(open(filename, 'rb').read(), filename=filename)
+        except SyntaxError:
+            print('{0}: failed parsing with {1}:'.format(
+                filename, interpreter,
+            ))
+            print('\n{0}'.format(
+                '    ' + traceback.format_exc().replace('\n', '\n    ')
+            ))
+            retval = 1
+    return retval
+
+
+if __name__ == '__main__':
+    exit(check_ast())
diff --git a/setup.py b/setup.py
index 7a66dcf..4fefeaa 100644
--- a/setup.py
+++ b/setup.py
@@ -38,6 +38,7 @@ setup(
         'console_scripts': [
             'autopep8-wrapper = pre_commit_hooks.autopep8_wrapper:main',
             'check-added-large-files = pre_commit_hooks.check_added_large_files:main',
+            'check-ast = pre_commit_hooks.check_ast:check_ast',
             'check-case-conflict = pre_commit_hooks.check_case_conflict:main',
             'check-docstring-first = pre_commit_hooks.check_docstring_first:main',
             'check-json = pre_commit_hooks.check_json:check_json',
diff --git a/tests/check_ast_test.py b/tests/check_ast_test.py
new file mode 100644
index 0000000..64916ba
--- /dev/null
+++ b/tests/check_ast_test.py
@@ -0,0 +1,15 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+from pre_commit_hooks.check_ast import check_ast
+from testing.util import get_resource_path
+
+
+def test_failing_file():
+    ret = check_ast([get_resource_path('cannot_parse_ast.notpy')])
+    assert ret == 1
+
+
+def test_passing_file():
+    ret = check_ast([__file__])
+    assert ret == 0