Propagate the stdin_display_name to checker and processor

This way plugins like flake8-putty can have access to the correct filename.

src/flake8/checker.py

@@ -398,20 +398,20 @@ class FileChecker(object):
         :type style_guide:
             flake8.style_guide.StyleGuide
         """
-        self.filename = filename
         self.checks = checks
         self.style_guide = style_guide
         self.results = []
-        self.processor = self._make_processor()
+        self.processor = self._make_processor(filename)
+        self.filename = self.processor.filename
         self.statistics = {
             'tokens': 0,
             'logical lines': 0,
             'physical lines': len(self.processor.lines),
         }
 
-    def _make_processor(self):
+    def _make_processor(self, filename):
         try:
-            return processor.FileProcessor(self.filename,
+            return processor.FileProcessor(filename,
                                            self.style_guide.options)
         except IOError:
             # If we can not read the file due to an IOError (e.g., the file

src/flake8/main/options.py

@@ -74,7 +74,7 @@ def register_default_options(option_manager):
     )
 
     add_option(
-        '--stdin-display-name', default='stdin',
+        '--stdin-display-name',
         help='The name used when reporting errors from code passed via stdin.'
              ' This is useful for editors piping the file contents to flake8.'
              ' (Default: %default)',

src/flake8/processor.py

@@ -55,12 +55,13 @@ class FileProcessor(object):
         :param str filename:
             Name of the file to process
         """
+        self.options = options
         self.filename = filename
         self.lines = lines
         if lines is None:
-            self.lines = self.read_lines()
+            # allow for stdin filename substitution
+            self.filename, self.lines = self.read_lines(filename)
         self.strip_utf_bom()
-        self.options = options
 
         # Defaults for public attributes
         #: Number of preceding blank lines
@@ -268,13 +269,15 @@ class FileProcessor(object):
             self.indent_char = line[0]
         return line
 
-    def read_lines(self):
+    def read_lines(self, filename):
         # type: () -> List[str]
         """Read the lines for this file checker."""
-        if self.filename is None or self.filename == '-':
-            self.filename = 'stdin'
-            return self.read_lines_from_stdin()
-        return self.read_lines_from_filename()
+        if filename is None or filename == '-':
+            filename = self.options.stdin_display_name or 'stdin'
+            lines = self.read_lines_from_stdin()
+        else:
+            lines = self.read_lines_from_filename()
+        return (filename, lines)
 
     def _readlines_py2(self):
         # type: () -> List[str]

src/flake8/style_guide.py

@@ -260,8 +260,6 @@ class StyleGuide(object):
         """
         error = Error(code, filename, line_number, column_number, text,
                       physical_line)
-        if error.filename is None or error.filename == '-':
-            error = error._replace(filename=self.options.stdin_display_name)
         error_is_selected = (self.should_report_error(error.code) is
                              Decision.Selected)
         is_not_inline_ignored = self.is_inline_ignored(error) is False

tests/unit/test_file_processor.py

@@ -14,6 +14,7 @@ def options_from(**kwargs):
     kwargs.setdefault('hang_closing', True)
     kwargs.setdefault('max_line_length', 79)
     kwargs.setdefault('verbose', False)
+    kwargs.setdefault('stdin_display_name', None)
     return optparse.Values(kwargs)
 
 
@@ -63,13 +64,17 @@ def test_read_lines_from_stdin(stdin_get_value):
 
 
 @mock.patch('flake8.utils.stdin_get_value')
-def test_read_lines_sets_filename_attribute(stdin_get_value):
+def test_stdin_filename_attribute(stdin_get_value):
     """Verify that we update the filename attribute."""
     stdin_value = mock.Mock()
     stdin_value.splitlines.return_value = []
     stdin_get_value.return_value = stdin_value
     file_processor = processor.FileProcessor('-', options_from())
     assert file_processor.filename == 'stdin'
+    file_processor = processor.FileProcessor('-', options_from(
+        stdin_display_name="foo.py"
+    ))
+    assert file_processor.filename == 'foo.py'
 
 
 def test_line_for():