Fix bug with '# noqa' filtering (#3993)

lib/spack/spack/cmd/flake8.py

@@ -139,14 +139,6 @@ def filter_file(source, dest, output=False):
                 # We still want to catch trailing whitespace warnings
                 line = line.rstrip('\n')
 
-                if line == '# flake8: noqa':
-                    # Entire file is ignored
-                    break
-
-                if line.endswith('# noqa'):
-                    # Line is already ignored
-                    continue
-
                 for file_pattern, errors in exemptions.items():
                     if not file_pattern.search(source):
                         continue
@@ -154,7 +146,10 @@ def filter_file(source, dest, output=False):
                     for code, patterns in errors.items():
                         for pattern in patterns:
                             if pattern.search(line):
-                                if '# noqa: ' in line:
+                                if line.endswith('# noqa'):
+                                    # Line is already ignored
+                                    pass
+                                elif '# noqa: ' in line:
                                     line += ',{0}'.format(code)
                                 else:
                                     line += '  # noqa: {0}'.format(code)

var/spack/repos/builtin.mock/packages/flake8/package.py

@@ -71,6 +71,10 @@ class Flake8(Package):
     patch('hyper-specific-patch-that-fixes-some-random-bug-that-probably-only-affects-one-user.patch', when='%gcc@3.2.2:3.2.3')
 
     def install(self, spec, prefix):
+        # Make sure lines with '# noqa' work as expected. Don't just
+        # remove them entirely. This will mess up the indentation of
+        # the following lines.
+        if 'really-long-if-statement' != 'that-goes-over-the-line-length-limit-and-requires-noqa':  # noqa
             pass
 
     # '@when' decorated functions are exempt from redefinition errors