Suppport per-file '# flake8: noqa [ignore_codes]'

docs/source/user/violations.rst

@@ -136,6 +136,13 @@ the errors in that file will show up without having to modify our
 configuration. Both exist so we can choose which is better for us.
 
 
+Ignoring Specific Errors within a File
+--------------------------------------
+
+.. code-block:: python
+
+    # flake8: noqa E221,E222
+
 
 Selecting Violations with Flake8
 ================================

src/flake8/checker.py

@@ -1,5 +1,6 @@
 """Checker Manager and Checker classes."""
 import collections
+import copy
 import errno
 import itertools
 import logging
@@ -368,7 +369,7 @@ class FileChecker(object):
         :type options:
             argparse.Namespace
         """
-        self.options = options
+        self.options = copy.copy(options)
         self.filename = filename
         self.checks = checks
         # fmt: off
@@ -384,7 +385,13 @@ class FileChecker(object):
         self.should_process = False
         if self.processor is not None:
             self.display_name = self.processor.filename
-            self.should_process = not self.processor.should_ignore_file()
+            should_ignore = self.processor.should_ignore_file()
+            if isinstance(should_ignore, list):
+                self.options.ignore += should_ignore
+                self.should_process = True
+            else:
+                self.should_process = not should_ignore
+
             self.statistics["physical lines"] = len(self.processor.lines)
 
     def __repr__(self):  # type: () -> str

src/flake8/defaults.py

@@ -40,4 +40,5 @@ NOQA_INLINE_REGEXP = re.compile(
     re.IGNORECASE,
 )
 
-NOQA_FILE = re.compile(r"\s*# flake8[:=]\s*noqa", re.I)
+NOQA_FILE = re.compile(
+    r"\s*# flake8[:=]\s*noqa(?P<codes>\s*([A-Z]+[0-9]+(?:[,\s]+)?)+)?", re.I)

src/flake8/processor.py

@@ -338,18 +338,26 @@ class FileProcessor(object):
 
     def should_ignore_file(self):
         # type: () -> bool
-        """Check if ``flake8: noqa`` is in the file to be ignored.
+        """Check if ``flake8: noqa [Codes]`` is in the file to be ignored.
 
         :returns:
             True if a line matches :attr:`defaults.NOQA_FILE`,
+            or a list of codes to ignore if specified,
             otherwise False
         :rtype:
             bool
         """
-        if not self.options.disable_noqa and any(
-            defaults.NOQA_FILE.match(line) for line in self.lines
-        ):
-            return True
+        if not self.options.disable_noqa:
+            found_flake_noqa_line = False
+            ignore_codes = []
+            for line in self.lines:
+                matchobj = defaults.NOQA_FILE.match(line)
+                if matchobj:
+                    found_flake_noqa_line = True
+                    codes = matchobj.groupdict(default="")["codes"].split(",")
+                    codes = (code.strip() for code in codes)
+                    ignore_codes.extend(code for code in codes if code)
+            return ignore_codes or found_flake_noqa_line
         elif any(defaults.NOQA_FILE.search(line) for line in self.lines):
             LOG.warning(
                 "Detected `flake8: noqa` on line with code. To ignore an "

tests/unit/test_file_processor.py

@@ -61,6 +61,8 @@ def test_strip_utf_bom(first_line, default_options):
     (['\xEF\xBB\xBF"""Module docstring."""\n'], False),
     ([u'\uFEFF"""Module docstring."""\n'], False),
     (['#!/usr/bin/python', '# flake8 is great', 'a = 1'], False),
+    (['#!/usr/bin/python', '# flake8: noqa E221'], ["E221"]),
+    (['#!/usr/bin/python', '# flake8: noqa E220,E221'], ["E220", "E221"]),
     (['#!/usr/bin/python', '# flake8: noqa', 'a = 1'], True),
     (['#!/usr/bin/python', '# flake8:noqa', 'a = 1'], True),
     (['# flake8: noqa', '#!/usr/bin/python', 'a = 1'], True),
@@ -73,14 +75,24 @@ def test_strip_utf_bom(first_line, default_options):
 def test_should_ignore_file(lines, expected, default_options):
     """Verify that we ignore a file if told to."""
     file_processor = processor.FileProcessor('-', default_options, lines)
-    assert file_processor.should_ignore_file() is expected
+    assert file_processor.should_ignore_file() == expected
 
 
 def test_should_ignore_file_to_handle_disable_noqa(default_options):
     """Verify that we ignore a file if told to."""
     lines = ['# flake8: noqa']
     file_processor = processor.FileProcessor('-', default_options, lines)
-    assert file_processor.should_ignore_file() is True
+    assert file_processor.should_ignore_file()
+    default_options.disable_noqa = True
+    file_processor = processor.FileProcessor('-', default_options, lines)
+    assert file_processor.should_ignore_file() is False
+
+
+def test_should_ignore_file_to_handle_disable_noqa_opts(default_options):
+    """Verify that we ignore a file if told to."""
+    lines = ['# flake8: noqa E220,E221']
+    file_processor = processor.FileProcessor('-', default_options, lines)
+    assert file_processor.should_ignore_file() == ["E220", "E221"]
     default_options.disable_noqa = True
     file_processor = processor.FileProcessor('-', default_options, lines)
     assert file_processor.should_ignore_file() is False