Add JSON output format for output

tests/test_cli.py

@@ -619,6 +619,23 @@ def test_github_actions_detection(self):
         self.assertEqual(
             (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
 
+    def test_run_format_json(self):
+        path = os.path.join(self.wd, 'a.yaml')
+
+        with RunContext(self) as ctx:
+            cli.run((path, '--format', 'json'))
+        expected_out = (
+            '[\n    '
+            '{"file": "' + str(path) + '", "level": "error", "line": 2, '
+            '"column": 4, "description": "trailing spaces", '
+            '"rule": "trailing-spaces"},\n    '
+            '{"file": "' + str(path) + '", "level": "error", "line": 3, '
+            '"column": 4, "description": "no new line character at the end '
+            'of file", "rule": '
+            '"new-line-at-end-of-file"}\n]\n')
+        self.assertEqual(
+            (ctx.returncode, ctx.stdout, ctx.stderr), (1, expected_out, ''))
+
     def test_run_read_from_stdin(self):
         # prepares stdin with an invalid yaml string so that we can check
         # for its specific error, and be assured that stdin was read

yamllint/cli.py

@@ -14,6 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 import argparse
+import json
 import locale
 import os
 import platform
@@ -87,19 +88,45 @@ def github(problem, filename):
         line += problem.desc
         return line
 
+    @staticmethod
+    def json(problem, filename):
+        return json.dumps({
+            'file': filename,
+            'level': problem.level,
+            'line': problem.line,
+            'column': problem.column,
+            'description': problem.desc,
+            'rule': problem.rule,
+        })
+
+    @staticmethod
+    def json_pre_all():
+        return "["
+
+    @staticmethod
+    def json_post_all():
+        return "]"
+
 
 def show_problems(problems, file, args_format, no_warn):
     max_level = 0
     first = True
 
+
     if args_format == 'auto':
         if ('GITHUB_ACTIONS' in os.environ and
                 'GITHUB_WORKFLOW' in os.environ):
             args_format = 'github'
         elif supports_color():
             args_format = 'colored'
 
-    for problem in problems:
+    if args_format == "json":
+        print(Format.json_pre_all())
+
+    problems_list = list(problems)
+    size = len(problems_list)
+
+    for index, problem in enumerate(problems_list):
         max_level = max(max_level, PROBLEM_LEVELS[problem.level])
         if no_warn and (problem.level != 'error'):
             continue
@@ -115,6 +142,9 @@ def show_problems(problems, file, args_format, no_warn):
                 print(f'\033[4m{file}\033[0m')
                 first = False
             print(Format.standard_color(problem, file))
+        elif args_format == 'json':
+            print('    ' + Format.json(problem, file) + 
+                  ("" if index == size - 1 else "," ))
         else:
             if first:
                 print(file)
@@ -124,6 +154,9 @@ def show_problems(problems, file, args_format, no_warn):
     if not first and args_format == 'github':
         print('::endgroup::')
 
+    if args_format == "json":
+        print(Format.json_post_all())
+
     if not first and args_format != 'parsable':
         print('')
 
@@ -163,7 +196,7 @@ def run(argv=None):
                         help='list files to lint and exit')
     parser.add_argument('-f', '--format',
                         choices=('parsable', 'standard', 'colored', 'github',
-                                 'auto'),
+                                 'json', 'auto'),
                         default='auto', help='format for parsing output')
     parser.add_argument('-s', '--strict',
                         action='store_true',