Add a hook for checking parseable json.

hooks.yaml

@@ -1,3 +1,9 @@
+-   id: check-json
+    name: Check JSON
+    description: This hook checks json files for parseable syntax.
+    entry: check-json
+    language: python
+    files: \.json$
 -   id: check-yaml
     name: Check Yaml
     description: This hook checks yaml files for parseable syntax.
@@ -15,7 +21,7 @@
     description: Ensures that a file is either empty, or ends with one newline.
     entry: end-of-file-fixer
     language: python
-    files: \.(js|rb|md|py|scss|sh|tmpl|txt|yaml|yml)$
+    files: \.(js|json|rb|md|py|scss|sh|tmpl|txt|yaml|yml)$
 -   id: flake8
     name: Flake8
     description: This hook runs flake8.
@@ -39,4 +45,4 @@
     description: This hook trims trailing whitespace.
     entry: trailing-whitespace-fixer
     language: python
-    files: \.(js|rb|md|py|scss|sh|tmpl|txt|yaml|yml)$
+    files: \.(js|json|rb|md|py|scss|sh|tmpl|txt|yaml|yml)$

pre_commit_hooks/check_json.py

@@ -0,0 +1,27 @@
+from __future__ import print_function
+
+import argparse
+import sys
+import simplejson
+
+from pre_commit_hooks.util import entry
+
+
+@entry
+def check_json(argv):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='JSON filenames to check.')
+    args = parser.parse_args(argv)
+
+    retval = 0
+    for filename in args.filenames:
+        try:
+            simplejson.load(open(filename))
+        except simplejson.JSONDecodeError as e:
+            print('{0}: Failed to json encode ({1})'.format(filename, e))
+            retval = 1
+    return retval
+
+
+if __name__ == '__main__':
+    sys.exit(check_json())

pre_commit_hooks/check_yaml.py

@@ -10,7 +10,7 @@ from pre_commit_hooks.util import entry
 @entry
 def check_yaml(argv):
     parser = argparse.ArgumentParser()
-    parser.add_argument('filenames', nargs='*', help='Filenames to check.')
+    parser.add_argument('filenames', nargs='*', help='Yaml filenames to check.')
     args = parser.parse_args(argv)
 
     retval = 0

setup.py

@@ -6,7 +6,7 @@ setup(
     name='pre_commit_hooks',
     description='Some out-of-the-box hooks for pre-commit.',
     url='https://github.com/pre-commit/pre-commit-hooks',
-    version='0.1.1',
+    version='0.2.0',
 
     author='Anthony Sottile',
     author_email='asottile@umich.edu',
@@ -32,6 +32,7 @@ setup(
     ],
     entry_points={
         'console_scripts': [
+            'check-json = pre_commit_hooks.check_json:check_json',
             'check-yaml = pre_commit_hooks.check_yaml:check_yaml',
             'debug-statement-hook = pre_commit_hooks.debug_statement_hook:debug_statement_hook',
             'end-of-file-fixer = pre_commit_hooks.end_of_file_fixer:end_of_file_fixer',

testing/resources/bad_json.notjson

@@ -0,0 +1,3 @@
+{
+    "hello": "world",
+}

testing/resources/ok_json.json

@@ -0,0 +1,3 @@
+{
+    "hello": "world"
+}

tests/check_json_test.py

@@ -0,0 +1,13 @@
+import pytest
+
+from pre_commit_hooks.check_json import check_json
+from testing.util import get_resource_path
+
+
+@pytest.mark.parametrize(('filename', 'expected_retval'), (
+    ('bad_json.notjson', 1),
+    ('ok_json.json', 0),
+))
+def test_check_json(filename, expected_retval):
+    ret = check_json([get_resource_path(filename)])
+    assert ret == expected_retval