Add more functionality to the BaseFormatter

Ensure setuptools knows about flake8.formatting

flake8/formatting/base.py

@@ -0,0 +1,105 @@
+"""The base class and interface for all formatting plugins."""
+from __future__ import print_function
+
+
+class BaseFormatter(object):
+    """Class defining the formatter interface.
+
+    .. attribute:: options
+
+        The options parsed from both configuration files and the command-line.
+
+    .. attribute:: filename
+
+        If specified by the user, the path to store the results of the run.
+
+    .. attribute:: output_fd
+
+        Initialized when the :meth:`start` is called. This will be a file
+        object opened for writing.
+
+    .. attribute:: newline
+
+        The string to add to the end of a line. This is only used when the
+        output filename has been specified.
+    """
+
+    def __init__(self, options):
+        """Initialize with the options parsed from config and cli.
+
+        This also calls a hook, :meth:`after_init`, so subclasses do not need
+        to call super to call this method.
+
+        :param optparse.Values options:
+            User specified configuration parsed from both configuration files
+            and the command-line interface.
+        """
+        self.options = options
+        self.filename = options.output_file
+        self.output_fd = None
+        self.newline = '\n'
+        self.after_init()
+
+    def after_init(self):
+        """Initialize the formatter further."""
+        pass
+
+    def start(self):
+        """Prepare the formatter to receive input.
+
+        This defaults to initializing :attr:`output_fd` if :attr:`filename`
+        """
+        if self.filename:
+            self.output_fd = open(self.filename, 'w')
+
+    def handle(self, error):
+        """Handle an error reported by Flake8.
+
+        This defaults to calling :meth:`format` and then :meth:`write`. To
+        extend how errors are handled, override this method.
+
+        :param error:
+            This will be an instance of :class:`~flake8.style_guide.Error`.
+        :type error:
+            flake8.style_guide.Error
+        """
+        line = self.format(error)
+        self.write(line)
+
+    def format(self, error):
+        """Format an error reported by Flake8.
+
+        This method **must** be implemented by subclasses.
+
+        :param error:
+            This will be an instance of :class:`~flake8.style_guide.Error`.
+        :type error:
+            flake8.style_guide.Error
+        :returns:
+            The formatted error string.
+        :rtype:
+            str
+        """
+        raise NotImplementedError('Subclass of BaseFormatter did not implement'
+                                  ' format.')
+
+    def write(self, line):
+        """Write the line either to the output file or stdout.
+
+        This handles deciding whether to write to a file or print to standard
+        out for subclasses. Override this if you want behaviour that differs
+        from the default.
+
+        :param str line:
+            The formatted string to print or write.
+        """
+        if self.output_fd is not None:
+            self.output_fd.write(line + self.newline)
+        else:
+            print(self.output_fd)
+
+    def stop(self):
+        """Clean up after reporting is finished."""
+        if self.output_fd is not None:
+            self.output_fd.close()
+            self.output_fd = None

setup.py

@@ -58,6 +58,7 @@ setuptools.setup(
     url="https://gitlab.com/pycqa/flake8",
     packages=[
         "flake8",
+        "flake8.formatting",
         "flake8.main",
         "flake8.options",
         "flake8.plugins",