Tools/Scripts/webkitpy/style/checkers/python.py

# Copyright (C) 2010 Chris Jerdonek (cjerdonek@webkit.org)
#
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# modification, are permitted provided that the following conditions
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# 1.  Redistributions of source code must retain the above copyright
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# 2.  Redistributions in binary form must reproduce the above copyright
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"""Supports checking WebKit style in Python files."""

import re
from StringIO import StringIO

from webkitpy.common.system.filesystem import FileSystem
from webkitpy.common.webkit_finder import WebKitFinder
from webkitpy.thirdparty.autoinstalled import pep8
from webkitpy.thirdparty.autoinstalled.pylint import lint
from webkitpy.thirdparty.autoinstalled.pylint.reporters.text import ParseableTextReporter


class PythonChecker(object):
    """Processes text lines for checking style."""
    def __init__(self, file_path, handle_style_error):
        self._file_path = file_path
        self._handle_style_error = handle_style_error

    def check(self, lines):
        self._check_pep8(lines)
        self._check_pylint(lines)

    def _check_pep8(self, lines):
        # Initialize pep8.options, which is necessary for
        # Checker.check_all() to execute.
        pep8.process_options(arglist=[self._file_path])

        pep8_checker = pep8.Checker(self._file_path)

        def _pep8_handle_error(line_number, offset, text, check):
            # FIXME: Incorporate the character offset into the error output.
            #        This will require updating the error handler __call__
            #        signature to include an optional "offset" parameter.
            pep8_code = text[:4]
            pep8_message = text[5:]

            category = "pep8/" + pep8_code

            self._handle_style_error(line_number, category, 5, pep8_message)

        pep8_checker.report_error = _pep8_handle_error
        pep8_errors = pep8_checker.check_all()

    def _check_pylint(self, lines):
        pylinter = Pylinter()

        # FIXME: for now, we only report pylint errors, but we should be catching and
        # filtering warnings using the rules in style/checker.py instead.
        output = pylinter.run(['-E', self._file_path])

        lint_regex = re.compile('([^:]+):([^:]+): \[([^]]+)\] (.*)')
        for error in output.getvalue().splitlines():
            match_obj = lint_regex.match(error)
            assert(match_obj)
            line_number = int(match_obj.group(2))
            category_and_method = match_obj.group(3).split(', ')
            category = 'pylint/' + (category_and_method[0])
            if len(category_and_method) > 1:
                message = '[%s] %s' % (category_and_method[1], match_obj.group(4))
            else:
                message = match_obj.group(4)
            self._handle_style_error(line_number, category, 5, message)


class Pylinter(object):
    # We filter out these messages because they are bugs in pylint that produce false positives.
    # FIXME: Does it make sense to combine these rules with the rules in style/checker.py somehow?
    FALSE_POSITIVES = [
        # possibly http://www.logilab.org/ticket/98613 ?
        "Instance of 'Popen' has no 'poll' member",
        "Instance of 'Popen' has no 'returncode' member",
        "Instance of 'Popen' has no 'stdin' member",
        "Instance of 'Popen' has no 'stdout' member",
        "Instance of 'Popen' has no 'stderr' member",
        "Instance of 'Popen' has no 'wait' member",
        "Instance of 'Popen' has no 'pid' member",
    ]

    def __init__(self):
        self._pylintrc = WebKitFinder(FileSystem()).path_from_webkit_base('Tools', 'Scripts', 'webkitpy', 'pylintrc')

    def run(self, argv):
        output = _FilteredStringIO(self.FALSE_POSITIVES)
        lint.Run(['--rcfile', self._pylintrc] + argv, reporter=ParseableTextReporter(output=output), exit=False)
        return output


class _FilteredStringIO(StringIO):
    def __init__(self, bad_messages):
        StringIO.__init__(self)
        self.dropped_last_msg = False
        self.bad_messages = bad_messages

    def write(self, msg=''):
        if not self._filter(msg):
            StringIO.write(self, msg)

    def _filter(self, msg):
        if any(bad_message in msg for bad_message in self.bad_messages):
            self.dropped_last_msg = True
            return True
        if self.dropped_last_msg:
            # We drop the newline after a dropped message as well.
            self.dropped_last_msg = False
            if msg == '\n':
                return True
        return False