for pretty-format-json add option: --empty-object-with-newline

pre_commit_hooks/pretty_format_json.py

@@ -3,10 +3,15 @@ from __future__ import annotations
 import argparse
 import json
 import sys
+import re
+
 from difflib import unified_diff
 from typing import Mapping
 from typing import Sequence
 
+def _insert_linebreaks(json_str) -> str:
+    # (?P<spaces>\s*) seems to capture the \n. Hence, there is no need for it in the substitution string
+    return re.sub(r'\n(?P<spaces>\s*)(?P<json_key>.*): {}(?P<delim>,??)', '\n\g<spaces>\g<json_key>: {\n\g<spaces>}\g<delim>', json_str)
 
 def _get_pretty_format(
         contents: str,
@@ -14,6 +19,7 @@ def _get_pretty_format(
         ensure_ascii: bool = True,
         sort_keys: bool = True,
         top_keys: Sequence[str] = (),
+        empty_object_with_newline: bool = False,
 ) -> str:
     def pairs_first(pairs: Sequence[tuple[str, str]]) -> Mapping[str, str]:
         before = [pair for pair in pairs if pair[0] in top_keys]
@@ -27,6 +33,8 @@ def _get_pretty_format(
         indent=indent,
         ensure_ascii=ensure_ascii,
     )
+    if empty_object_with_newline:
+        json_pretty = _insert_linebreaks(json_pretty)
     return f'{json_pretty}\n'
 
 
@@ -96,6 +104,13 @@ def main(argv: Sequence[str] | None = None) -> int:
         default=[],
         help='Ordered list of keys to keep at the top of JSON hashes',
     )
+    parser.add_argument(
+        '--empty-object-with-newline',
+        action='store_true',
+        dest='empty_object_with_newline',
+        default=False,
+        help='Format empty JSON objects to have a linebreak, also activates --no-sort-keys',
+    )
     parser.add_argument('filenames', nargs='*', help='Filenames to fix')
     args = parser.parse_args(argv)
 
@@ -106,9 +121,12 @@ def main(argv: Sequence[str] | None = None) -> int:
             contents = f.read()
 
         try:
+            if args.empty_object_with_newline:
+                args.no_sort_keys = True
             pretty_contents = _get_pretty_format(
                 contents, args.indent, ensure_ascii=not args.no_ensure_ascii,
                 sort_keys=not args.no_sort_keys, top_keys=args.top_keys,
+                empty_object_with_newline=args.empty_object_with_newline
             )
         except ValueError:
             print(
@@ -118,13 +136,15 @@ def main(argv: Sequence[str] | None = None) -> int:
             return 1
 
         if contents != pretty_contents:
+            status = 1
             if args.autofix:
                 _autofix(json_file, pretty_contents)
+                if args.empty_object_with_newline:
+                    status = 0
             else:
                 diff_output = get_diff(contents, pretty_contents, json_file)
                 sys.stdout.buffer.write(diff_output.encode())
 
-            status = 1
 
     return status
 

testing/resources/empty_object_json_multiline.json

@@ -0,0 +1,17 @@
+{
+  "empty": {
+  },
+  "inhabited": {
+    "person": {
+      "name": "Roger",
+      "nested_empty_with_comma": {
+      },
+      "array": [
+        {
+          "nested_empty_in_array": {
+          }
+        }
+      ]
+    }
+  }
+}

testing/resources/empty_object_json_sameline.json

@@ -0,0 +1,14 @@
+{
+  "empty": {},
+  "inhabited": {
+    "person": {
+      "name": "Roger",
+      "nested_empty_with_comma": {},
+      "array": [
+        {
+          "nested_empty_in_array": {}
+        }
+      ]
+    }
+  }
+}

tests/pretty_format_json_test.py

@@ -4,6 +4,7 @@ import os
 import shutil
 
 import pytest
+import filecmp
 
 from pre_commit_hooks.pretty_format_json import main
 from pre_commit_hooks.pretty_format_json import parse_num_to_int
@@ -137,3 +138,32 @@ def test_diffing_output(capsys):
     assert actual_retval == expected_retval
     assert actual_out == expected_out
     assert actual_err == ''
+
+
+def test_empty_object_with_newline(tmpdir):
+    # same line objects shoud trigger with --empty-object-with-newline switch
+    sameline = get_resource_path("empty_object_json_sameline.json")
+    ret = main(["--empty-object-with-newline", str(sameline)])
+    assert ret == 1
+
+    multiline = get_resource_path("empty_object_json_multiline.json")
+    to_be_formatted_sameline = tmpdir.join(
+        "not_pretty_formatted_empty_object_json_sameline.json"
+    )
+    shutil.copyfile(str(sameline), str(to_be_formatted_sameline))
+
+    # file has empty object with newline => expect fail with default settings
+    ret = main([str(multiline)])
+    assert ret == 1
+
+    # now launch the autofix with empty object with newline support on that file
+    ret = main(
+        ["--autofix", "--empty-object-with-newline", str(to_be_formatted_sameline)]
+    )
+    # it should have formatted it and don't raise an error code
+    assert ret == 0
+
+    # file was formatted (shouldn't trigger linter with --empty-object-with-newline switch)
+    ret = main(["--empty-object-with-newline", str(to_be_formatted_sameline)])
+    assert ret == 0
+    assert filecmp.cmp(to_be_formatted_sameline, multiline)