Fix handling of logical lines with noqa

When attempting to centralize all inline NoQA handling in the StyleGuide
we inadvertently broke plugins relying on it in combination with checker
state. For example, the check for E402 relies both on NoQA and the state
to determine if it has seen a non-import line. Placing NoQA on the sole
line that is not an import is more elegant than placing it on each of
the following import lines.

Closes #186

docs/source/release-notes/3.0.2.rst

@@ -6,7 +6,12 @@
 - Fix indexing of column numbers. We accidentally were starting column indices
   at 0 instead of 1.
 
+- Fix regression in handling of errors like E402 that rely on a combination of
+  attributes. (See also `GitLab#186`_)
+
 
 .. links
 .. _GitLab#181:
     https://gitlab.com/pycqa/flake8/issues/181
+.. _GitLab#186:
+    https://gitlab.com/pycqa/flake8/issues/186

setup.py

@@ -7,9 +7,9 @@ import sys
 
 import setuptools
 
-sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'src'))  # noqa
 
-import flake8  # noqa
+import flake8
 
 
 tests_require = ['mock', 'pytest']

src/flake8/defaults.py

@@ -1,4 +1,5 @@
 """Constants that define defaults."""
+import re
 
 EXCLUDE = '.svn,CVS,.bzr,.hg,.git,__pycache__,.tox,.eggs,*.egg'
 IGNORE = 'E121,E123,E126,E226,E24,E704,W503,W504'
@@ -15,3 +16,19 @@ STATISTIC_NAMES = (
     'physical lines',
     'tokens',
 )
+
+NOQA_INLINE_REGEXP = re.compile(
+    # We're looking for items that look like this:
+    # ``# noqa``
+    # ``# noqa: E123``
+    # ``# noqa: E123,W451,F921``
+    # ``# NoQA: E123,W451,F921``
+    # ``# NOQA: E123,W451,F921``
+    # We do not care about the ``: `` that follows ``noqa``
+    # We do not care about the casing of ``noqa``
+    # We want a comma-separated list of errors
+    '# noqa(?:: (?P<codes>[A-Z0-9,]+))?',
+    re.IGNORECASE
+)
+
+NOQA_FILE = re.compile(r'\s*# flake8[:=]\s*noqa', re.I)

src/flake8/processor.py

@@ -2,7 +2,6 @@
 import contextlib
 import io
 import logging
-import re
 import sys
 import tokenize
 
@@ -47,8 +46,6 @@ class FileProcessor(object):
     - :attr:`verbose`
     """
 
-    NOQA_FILE = re.compile(r'\s*# flake8[:=]\s*noqa', re.I)
-
     def __init__(self, filename, options, lines=None):
         """Initialice our file processor.
 
@@ -147,6 +144,7 @@ class FileProcessor(object):
             self.previous_logical = self.logical_line
         self.blank_lines = 0
         self.tokens = []
+        self.noqa = False
 
     def build_logical_line_tokens(self):
         """Build the mapping, comments, and logical line lists."""
@@ -189,9 +187,12 @@ class FileProcessor(object):
     def build_logical_line(self):
         """Build a logical line from the current tokens list."""
         comments, logical, mapping_list = self.build_logical_line_tokens()
+        joined_comments = ''.join(comments)
         self.logical_line = ''.join(logical)
+        if defaults.NOQA_INLINE_REGEXP.search(joined_comments):
+            self.noqa = True
         self.statistics['logical lines'] += 1
-        return ''.join(comments), self.logical_line, mapping_list
+        return joined_comments, self.logical_line, mapping_list
 
     def split_line(self, token):
         """Split a physical line's line based on new-lines.
@@ -316,12 +317,12 @@ class FileProcessor(object):
         """Check if ``# flake8: noqa`` is in the file to be ignored.
 
         :returns:
-            True if a line matches :attr:`FileProcessor.NOQA_FILE`,
+            True if a line matches :attr:`defaults.NOQA_FILE`,
             otherwise False
         :rtype:
             bool
         """
-        ignore_file = self.NOQA_FILE.search
+        ignore_file = defaults.NOQA_FILE.search
         return any(ignore_file(line) for line in self.lines)
 
     def strip_utf_bom(self):

src/flake8/style_guide.py

@@ -3,8 +3,8 @@ import collections
 import enum
 import linecache
 import logging
-import re
 
+from flake8 import defaults
 from flake8 import statistics
 from flake8 import utils
 
@@ -53,20 +53,6 @@ Error = collections.namedtuple(
 class StyleGuide(object):
     """Manage a Flake8 user's style guide."""
 
-    NOQA_INLINE_REGEXP = re.compile(
-        # We're looking for items that look like this:
-        # ``# noqa``
-        # ``# noqa: E123``
-        # ``# noqa: E123,W451,F921``
-        # ``# NoQA: E123,W451,F921``
-        # ``# NOQA: E123,W451,F921``
-        # We do not care about the ``: `` that follows ``noqa``
-        # We do not care about the casing of ``noqa``
-        # We want a comma-separated list of errors
-        '# noqa(?:: (?P<codes>[A-Z0-9,]+))?',
-        re.IGNORECASE
-    )
-
     def __init__(self, options, listener_trie, formatter):
         """Initialize our StyleGuide.
 
@@ -177,7 +163,7 @@ class StyleGuide(object):
         if physical_line is None:
             physical_line = linecache.getline(error.filename,
                                               error.line_number)
-        noqa_match = self.NOQA_INLINE_REGEXP.search(physical_line)
+        noqa_match = defaults.NOQA_INLINE_REGEXP.search(physical_line)
         if noqa_match is None:
             LOG.debug('%r is not inline ignored', error)
             return False