Add new hook pretty-format-json

This new hook allows to standardize one's JSON files (sorted key/4
spaces indent).
By default it just fails if any file is not complying with the standard,
but you can also pass the arg `--autofix` and the hook will
pretty-format the file itself.

Good in use combined with the `check-json` hook.

README.md

@@ -45,6 +45,7 @@ Add this to your `.pre-commit-config.yaml`
 - `name-tests-test` - Assert that files in tests/ end in `_test.py`.
     - Use `args: ['--django']` to match `test*.py` instead.
 - `pyflakes` - Run pyflakes on your python files.
+- `pretty-format-json` - Checks that all your JSON files are pretty
 - `requirements-txt-fixer` - Sorts entries in requirements.txt
 - `trailing-whitespace` - Trims trailing whitespace.
     - Markdown linebreak trailing spaces preserved for `.md` and`.markdown`;

hooks.yaml

@@ -31,6 +31,12 @@
     entry: check-json
     language: python
     files: \.json$
+-   id: pretty-format-json
+    name: Pretty format JSON
+    description: This hook sets a standard for formatting JSON files.
+    entry: pretty-format-json
+    language: python
+    files: \.json$
 -   id: check-merge-conflict
     name: Check for merge conflicts
     description: Check for files that contain merge conflict strings.

pre_commit_hooks/pretty_format_json.py

@@ -0,0 +1,70 @@
+from __future__ import print_function
+
+import argparse
+import sys
+
+import simplejson
+
+
+def _get_pretty_format(contents, indent):
+    return simplejson.dumps(
+        simplejson.loads(contents),
+        sort_keys=True,
+        indent=indent
+    ) + "\n"  # dumps don't end with a newline
+
+
+def _autofix(filename, new_contents):
+    print("Fixing file {0}".format(filename))
+    with open(filename, 'w') as f:
+        f.write(new_contents)
+
+
+def pretty_format_json(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        '--autofix',
+        action='store_true',
+        dest='autofix',
+        help='Automatically fixes encountered not-pretty-formatted files'
+    )
+    parser.add_argument(
+        '--indent',
+        type=int,
+        default=2,
+        help='Number of indent spaces used to pretty-format files'
+    )
+
+    parser.add_argument('filenames', nargs='*', help='Filenames to fix')
+    args = parser.parse_args(argv)
+
+    status = 0
+
+    for json_file in args.filenames:
+        try:
+            f = open(json_file, 'r')
+            contents = f.read()
+            f.close()
+
+            pretty_contents = _get_pretty_format(contents, args.indent)
+
+            if contents != pretty_contents:
+                print("File {0} is not pretty-formatted".format(json_file))
+
+                if args.autofix:
+                    _autofix(json_file, pretty_contents)
+
+                status = 1
+
+        except simplejson.JSONDecodeError:
+            print(
+                "Input File {0} is not a valid JSON, consider using check-json"
+                .format(json_file)
+            )
+            return 1
+
+    return status
+
+
+if __name__ == '__main__':
+    sys.exit(pretty_format_json())

setup.py

@@ -39,15 +39,16 @@ setup(
             'check-added-large-files = pre_commit_hooks.check_added_large_files:main',
             'check-case-conflict = pre_commit_hooks.check_case_conflict:main',
             'check-docstring-first = pre_commit_hooks.check_docstring_first:main',
-            'check-merge-conflict = pre_commit_hooks.check_merge_conflict:detect_merge_conflict',
             'check-json = pre_commit_hooks.check_json:check_json',
+            'check-merge-conflict = pre_commit_hooks.check_merge_conflict:detect_merge_conflict',
             'check-xml = pre_commit_hooks.check_xml:check_xml',
             'check-yaml = pre_commit_hooks.check_yaml:check_yaml',
             'debug-statement-hook = pre_commit_hooks.debug_statement_hook:debug_statement_hook',
             'detect-private-key = pre_commit_hooks.detect_private_key:detect_private_key',
+            'double-quote-string-fixer = pre_commit_hooks.string_fixer:main',
             'end-of-file-fixer = pre_commit_hooks.end_of_file_fixer:end_of_file_fixer',
             'name-tests-test = pre_commit_hooks.tests_should_end_in_test:validate_files',
-            'double-quote-string-fixer = pre_commit_hooks.string_fixer:main',
+            'pretty-format-json = pre_commit_hooks.pretty_format_json:pretty_format_json',
             'requirements-txt-fixer = pre_commit_hooks.requirements_txt_fixer:fix_requirements_txt',
             'trailing-whitespace-fixer = pre_commit_hooks.trailing_whitespace_fixer:fix_trailing_whitespace',
         ],

testing/resources/not_pretty_formatted_json.json

@@ -0,0 +1,5 @@
+{
+    "foo": "bar",
+    "alist": [2, 34, 234],
+    "blah": null
+}

testing/resources/pretty_formatted_json.json

@@ -0,0 +1,9 @@
+{
+  "alist": [
+    2,
+    34,
+    234
+  ],
+  "blah": null,
+  "foo": "bar"
+}

tests/pretty_format_json_test.py

@@ -0,0 +1,40 @@
+import pytest
+import tempfile
+
+from pre_commit_hooks.pretty_format_json import pretty_format_json
+from testing.util import get_resource_path
+
+
+@pytest.mark.parametrize(('filename', 'expected_retval'), (
+    ('not_pretty_formatted_json.json', 1),
+    ('pretty_formatted_json.json', 0),
+))
+def test_pretty_format_json(filename, expected_retval):
+    ret = pretty_format_json([get_resource_path(filename)])
+    assert ret == expected_retval
+
+
+def test_autofix_pretty_format_json():
+    toformat_file = tempfile.NamedTemporaryFile(delete=False, mode='w+')
+
+    # copy our file to format there
+    model_file = open(get_resource_path('not_pretty_formatted_json.json'), 'r')
+    model_contents = model_file.read()
+    model_file.close()
+
+    toformat_file.write(model_contents)
+    toformat_file.close()
+
+    # now launch the autofix on that file
+    ret = pretty_format_json(['--autofix', toformat_file.name])
+    # it should have formatted it
+    assert ret == 1
+
+    # file already good
+    ret = pretty_format_json([toformat_file.name])
+    assert ret == 0
+
+
+def test_badfile_pretty_format_json():
+    ret = pretty_format_json([get_resource_path('ok_yaml.yaml')])
+    assert ret == 1