FilenameBear.py: Add filename length check

Adds the check if filename has length more than 260, so minimum of
maximum filename length on Windows and maximum filename length
on Unix-like systems. In that case, user will get message about it.

Closes coala#2003

bears/general/FilenameBear.py

@@ -26,6 +26,7 @@ class FilenameBear(LocalBear):
                                   }
 
     def run(self, filename, file,
+            max_filename_length: int=260,
             file_naming_convention: str=None,
             ignore_uppercase_filenames: bool=True,
             filename_prefix: str='',
@@ -42,6 +43,8 @@ def run(self, filename, file,
             - ``pascal`` (``ThisIsPascalCase``)
             - ``snake`` (``this_is_snake_case``)
             - ``space`` (``This Is Space Case``)
+        :param max_filename_length:
+            Maximum filename length on both Windows and Unix-like systems.
         :param ignore_uppercase_filenames:
             Whether or not to ignore fully uppercase filenames completely,
             e.g. COPYING, LICENSE etc.
@@ -98,6 +101,12 @@ def run(self, filename, file,
                 'Filename does not use the suffix {!r}.'.format(
                     filename_suffix))
 
+        if len(filename) > max_filename_length:
+            messages.append(
+                'Filename is too long ({} > {}).'.format(
+                    len(filename),
+                    max_filename_length))
+
         if ignore_uppercase_filenames and filename_without_extension.isupper():
             return
 

tests/general/FilenameBearTest.py

@@ -151,3 +151,42 @@ def test_file_prefix_suffix(self):
                                 severity=RESULT_SEVERITY.NORMAL,
                                 file='filename.xyz')],
             filename='filename.xyz')
+
+    def test_file_with_too_long_filename(self):
+        msg = 'Filename is too long ({} > {}).'
+        filename_test1 = '_filenamewhichistoolong'*15 + '.xyz'
+        filename_test2 = '_filenamewhichistoolong'*10 + '.xyz'
+        filename_test3 = '_validfilenamelength'*13
+        max_filename_length = 260
+        self.check_invalidity(
+            self.uut, [''], filename=filename_test1)
+        self.check_validity(
+            self.uut, [''], filename=filename_test2)
+        self.check_validity(
+            self.uut, [''], filename=filename_test3)
+        self.check_results(
+            self.uut,
+            [''],
+            [Result.from_values('FilenameBear',
+                                msg.format(len(filename_test1),
+                                           max_filename_length),
+                                severity=RESULT_SEVERITY.NORMAL,
+                                file=filename_test1)],
+            filename=filename_test1)
+
+    def test_message_too_long_file_with_other_errors(self):
+        self.section['filename_prefix'] = 'pre'
+        filename_test1 = '_filenamewhichistoolong'*15 + '.xyz'
+        max_filename_length = 260
+        msg = ("- Filename does not use the prefix 'pre'.\n"
+               '- Filename is too long ({} > {}).'
+               )
+        self.check_results(
+            self.uut,
+            [''],
+            [Result.from_values('FilenameBear',
+                                msg.format(len(filename_test1),
+                                           max_filename_length),
+                                severity=RESULT_SEVERITY.NORMAL,
+                                file=filename_test1)],
+            filename=filename_test1)