pylint: Add checker for open() without encoding.

.run_checks

@@ -12,7 +12,7 @@ exclude=test_.*,ez_setup
 
 [pylint]
 args=--output-format=colorized,--reports=no,--rcfile=.pylintrc
-plugins=config,crlf,modeline,settrace
+plugins=config,crlf,modeline,settrace,openencoding
 
 [flake8]
 args=--config=.flake8

doc/TODO

@@ -55,7 +55,6 @@ Downloads
 Improvements / minor features
 =============================
 
-- Add pylint checker to warn on open() without encoding.
 - We should have something like utils.debug.qenum_key for QFlags.
 - Honour icognito mode for cookies etc.
 - Make sure commands in config are _complete_

scripts/pylint_checkers/openencoding.py

@@ -0,0 +1,59 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Make sure open() has an encoding set."""
+
+from pylint.interfaces import IAstroidChecker
+from pylint.checkers import BaseChecker
+from pylint.checkers import utils
+
+
+class OpenEncodingChecker(BaseChecker):
+
+    """Checker to check open() has an encoding set."""
+
+    __implements__ = IAstroidChecker
+    name = 'open-encoding'
+
+    msgs = {
+        'W9400': ('open() called without encoding', 'open-without-encoding',
+                  None),
+    }
+
+    @utils.check_messages('open-without-encoding')
+    def visit_callfunc(self, node):
+        """Visit a CallFunc node."""
+        if hasattr(node, 'func'):
+            infer = utils.safe_infer(node.func)
+            if infer and infer.root().name == '_io':
+                if getattr(node.func, 'name', None) in ('open', 'file'):
+                    self._check_open_encoding(node)
+
+    def _check_open_encoding(self, node):
+        """Check that an open() call always has an encoding set."""
+        try:
+            _encoding = utils.get_argument_from_call(node, position=3,
+                                                     keyword='encoding')
+        except utils.NoSuchArgumentError:
+            self.add_message('open-without-encoding', node=node)
+
+
+def register(linter):
+    """Register this checker."""
+    linter.register_checker(OpenEncodingChecker(linter))