JSONFormatBear.py: Implement max_line_length

The max_line_length for JSON is infinity by default.
It can be modified if a user is sure about the line length.

Closes coala#2743

bears/js/JSONFormatBear.py

@@ -1,4 +1,5 @@
 import json
+import sys
 from collections import OrderedDict
 from re import match
 
@@ -23,18 +24,24 @@ class JSONFormatBear(LocalBear):
     @deprecate_settings(indent_size='tab_width',
                         escape_unicode=('keep_unicode', negate))
     def run(self, filename, file,
+            max_line_length: int = 0,
             json_sort: bool = False,
             indent_size: int = SpacingHelper.DEFAULT_TAB_WIDTH,
             escape_unicode: bool = True,
             ):
         """
         Raises issues for any deviations from the pretty-printed JSON.
 
-        :param json_sort:      Whether or not keys should be sorted.
-        :param indent_size:    Number of spaces per indentation level.
-        :param escape_unicode: Whether or not to escape unicode values using
-                               ASCII.
+        :param max_line_length: Maximum number of characters for a line.
+                                When set to 0 allows infinite line length.
+        :param json_sort:       Whether or not keys should be sorted.
+        :param indent_size:     Number of spaces per indentation level.
+        :param escape_unicode:  Whether or not to escape unicode values using
+                                ASCII.
         """
+        if not max_line_length:
+            max_line_length = sys.maxsize
+
         # Output a meaningful message if empty file given as input
         if len(file) == 0:
             yield Result.from_values(self,
@@ -56,6 +63,22 @@ def run(self, filename, file,
                 column=int(err_content.group(3)))
             return
 
+        for line_number, line in enumerate(file):
+            line = line.expandtabs(indent_size)
+            if len(line) > max_line_length + 1:
+                yield Result.from_values(
+                    origin=self,
+                    message='Line is longer than allowed.'
+                            ' ({actual} > {maximum})'.format(
+                                actual=len(line)-1,
+                                maximum=max_line_length),
+                    file=filename,
+                    line=line_number + 1,
+                    column=max_line_length + 1,
+                    end_line=line_number + 1,
+                    end_column=len(line),
+                    )
+
         corrected = json.dumps(json_content,
                                sort_keys=json_sort,
                                indent=indent_size,

tests/js/JSONFormatBearTest.py

@@ -35,6 +35,13 @@
 }"""
 
 
+# This will generate a line with 80 characters
+max_line_length_file1 = '{\n    "string": "' + 'a' * 64 + '"\n}'
+
+# This will generate a line with 79 characters
+max_line_length_file2 = '{\n    "string": "' + 'a' * 63 + '"\n}'
+
+
 class JSONTest(LocalBearTestHelper):
 
     def setUp(self):
@@ -91,3 +98,19 @@ def test_exception_empty_file(self):
                                               invalid_files=(),
                                               settings={'escape_unicode':
                                                         'false'})
+
+
+JSONFormatBearInfLineLengthTest = verify_local_bear(JSONFormatBear,
+                                                    valid_files=(
+                                                        max_line_length_file1,
+                                                        max_line_length_file2),
+                                                    invalid_files=())
+
+
+JSONFormatBearLineLengthTest = verify_local_bear(JSONFormatBear,
+                                                 valid_files=(
+                                                     max_line_length_file2,),
+                                                 invalid_files=(
+                                                     max_line_length_file1,),
+                                                 settings={'max_line_length':
+                                                           '79'})