Merge with default.

17 files changed, 338 insertions, 158 deletions

diff --git a/ChangeLog b/ChangeLog
index 228d9ab..a241958 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,10 +2,20 @@ ChangeLog for Pylint
 ====================
 
 --
-    * Add new warning for unpacking non-sequences in assignments
+    * Run pylint as a python module 'python -m pylint' (anatoly techtonik)
 
     * Check for non-exception classes inside an except clause
 
+    * epylint support options to give to pylint after the file to analyze and
+      have basic input validation (bitbucket #53 and #54), patches provided by
+      felipeochoa and Brian Lane
+
+    * Added a new warning, 'non-iterator-returned', for non-iterators 
+      returned by '__iter__'
+
+    * Add new warning for unpacking non-sequences in assignments
+
+
 2013-08-06  --  1.0.0
 
     * Add check for the use of 'exec' function
diff --git a/__main__.py b/__main__.py
new file mode 100644
index 0000000..7716361
--- /dev/null
+++ b/__main__.py
@@ -0,0 +1,3 @@
+#!/usr/bin/env python
+import pylint
+pylint.run_pylint()
diff --git a/checkers/classes.py b/checkers/classes.py
index 98a2f27..4c8022d 100644
--- a/checkers/classes.py
+++ b/checkers/classes.py
@@ -16,15 +16,21 @@
 """classes checker for Python code
 """
 from __future__ import generators
-
+import sys
 import astroid
 from astroid import YES, Instance, are_exclusive, AssAttr
+from astroid.bases import Generator
 
 from pylint.interfaces import IAstroidChecker
 from pylint.checkers import BaseChecker
 from pylint.checkers.utils import (PYMETHODS, overrides_a_method,
     check_messages, is_attr_private, is_attr_protected, node_frame_class)
 
+if sys.version_info >= (3, 0):
+    NEXT_METHOD = '__next__'
+else:
+    NEXT_METHOD = 'next'
+
 def class_is_abstract(node):
     """return true if the given class node should be considered as an abstract
     class
@@ -142,6 +148,11 @@ MSGS = {
               'non-parent-init-called',
               'Used when an __init__ method is called on a class which is not \
               in the direct ancestors for the analysed class.'),
+    'W0234': ('__iter__ returns non-iterator',
+              'non-iterator-returned',
+              'Used when an __iter__ method returns something which is not an \
+               iterable (i.e. has no `%s` method)' % NEXT_METHOD),
+
 
     }
 
@@ -311,6 +322,29 @@ a metaclass class method.'}
         except astroid.NotFoundError:
             pass
 
+        # check non-iterators in __iter__
+        if node.name == '__iter__':
+            self._check_iter(node)
+
+    def _check_iter(self, node):
+        try:
+            infered = node.infer_call_result(node)
+        except astroid.InferenceError:
+            return
+
+        for infered_node in infered:
+            if (infered_node is YES
+                or isinstance(infered_node, Generator)):
+                continue
+            if isinstance(infered_node, astroid.Instance):
+                try:
+                    infered_node.local_attr(NEXT_METHOD)
+                except astroid.NotFoundError:
+                    self.add_message('non-iterator-returned',
+                                     node=node)
+                    break
+
+
     def leave_function(self, node):
         """on method node, check if this method couldn't be a function
 
diff --git a/doc/Makefile b/doc/Makefile
index 8b8b3ec..98076a6 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -37,7 +37,7 @@ clean:
 	-rm -rf $(BUILDDIR)/*
 	-rm -f features.rst
 
-html: features.rst
+html: features
 	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
 	@echo
 	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."
@@ -131,7 +131,7 @@ doctest:
 	      "results in $(BUILDDIR)/doctest/output.txt."
 
 
-features.rst:
+features:
 	rm -f features.rst
 	echo "Pylint features" > features.rst
 	echo "===============" >> features.rst
diff --git a/doc/output.rst b/doc/output.rst
index 6617ac4..3a87547 100644
--- a/doc/output.rst
+++ b/doc/output.rst
@@ -24,20 +24,34 @@ obj
     object within the module (if any)
 msg
     text of the message
+msg_id
+    the message code (eg. I0011)
 symbol
-    symbolic name of the message
+    symbolic name of the message (eg. locally-disabled)
 C
     one letter indication of the message category
 category
     fullname of the message category
 
-For exemple the default format can be obtained with::
+For exemple the former (pre 1.0) default format can be obtained with::
 
-  pylint --msg-template='{sigle}:{line:3d},{column}: {obj}: {msg}'
+  pylint --msg-template='{msg_id}:{line:3d},{column}: {obj}: {msg}'
+
+A few other examples:
+
+* the new default format::
+
+    {C}:{line:3d},{column:2d}: {msg} ({symbol})
+
+* Visual Studio compatible format (former 'msvs' output format)::
+
+    {path}({line}): [{msg_id}{obj}] {msg}
+
+* Parseable (Emacs and all, former 'parseable' output format) format::
+
+    {path}:{line}: [{msg_id}({symbol}), {obj}] {msg}
 
-and a Visual Studio compatible format can be obtained with::
 
-  pylint --msg-template='{path}({line}): [{sigle}{obj}] {msg}'
 
 .. _Python new format syntax: http://docs.python.org/2/library/string.html#formatstrings
 
diff --git a/epylint.py b/epylint.py
index fbdfdac..76d7b68 100755
--- a/epylint.py
+++ b/epylint.py
@@ -29,7 +29,8 @@ For example:
         a/b/x.py
         a/c/y.py
 
-   - Then if y.py imports x as "from a.b import x" the following produces pylint errors
+   - Then if y.py imports x as "from a.b import x" the following produces pylint
+     errors
 
        cd a/c; pylint y.py
 
@@ -41,14 +42,15 @@ For example:
      we are checking we need to go out of it to avoid these false positives.
 
 
-You may also use py_run to run pylint with desired options and get back (or not) its output.
+You may also use py_run to run pylint with desired options and get back (or not)
+its output.
 """
 
 import sys, os, re
 from subprocess import Popen, PIPE
 
 
-def lint(filename):
+def lint(filename, options=None):
     """Pylint the given file.
 
     When run from emacs we will be in the directory of a file, and passed its filename.
@@ -74,8 +76,9 @@ def lint(filename):
     # Start pylint
     # Ensure we use the python and pylint associated with the running epylint
     lintPath = os.path.join(os.path.dirname(__file__), 'lint.py')
-    cmd = [sys.executable, lintPath, '--msg-template', '{path}:{line}: [{symbol}, {obj}] {msg}', '-r', 'n',
-           '--disable=C,R,I', childPath]
+    options = options or ['--disable=C,R,I']
+    cmd = [sys.executable, lintPath] + options + ['--msg-template',
+            '{path}:{line}: [{symbol}, {obj}] {msg}', '-r', 'n', childPath]
     process = Popen(cmd, stdout=PIPE, cwd=parentPath, universal_newlines=True)
 
     # The parseable line format is '%(path)s:%(line)s: [%(sigle)s%(obj)s] %(msg)s'
@@ -108,7 +111,7 @@ def lint(filename):
 
 def py_run(command_options='', return_std=False, stdout=None, stderr=None,
            script='epylint'):
-    """Run pylint from python (needs Python >= 2.4).
+    """Run pylint from python
 
     ``command_options`` is a string containing ``pylint`` command line options;
     ``return_std`` (boolean) indicates return of created standart output
@@ -158,7 +161,15 @@ def py_run(command_options='', return_std=False, stdout=None, stderr=None,
 
 
 def Run():
-    sys.exit(lint(sys.argv[1]))
+    if len(sys.argv) == 1:
+        print "Usage: %s <filename> [options]" % sys.argv[0]
+        sys.exit(1)
+    elif not os.path.exists(sys.argv[1]):
+        print "%s does not exist" % sys.argv[1] 
+        sys.exit(1)
+    else:
+        sys.exit(lint(sys.argv[1]))
+
 
 if __name__ == '__main__':
     Run()
diff --git a/gui.py b/gui.py
index 79a4089..0ee5974 100644
--- a/gui.py
+++ b/gui.py
@@ -39,10 +39,10 @@ COLORS = {'(I)':'lightblue',
 
 def convert_to_string(msg):
     """make a string representation of a message"""
-    if (msg[4] != ""):
-        return "(" + msg[0] + ") " + msg[3] + "." + msg[4] + " [" + msg[5] + "]: " + msg[6]
-    else:
-        return "(" + msg[0] + ") " + msg[3] + " [" + msg[5] + "]: " + msg[6]
+    module_object = msg.module
+    if msg.obj:
+        module_object += ".%s" % msg.obj
+    return "(%s) %s [%d]: %s" % (msg.C, module_object, msg.line, msg.msg)
 
 class BasicStream(object):
     '''
@@ -327,12 +327,7 @@ class LintGui(object):
         self.lbMessages.delete(0, END)
         self.visible_msgs = []
         for msg in self.msgs:
-
-            # Obtaining message type (pylint's '--include-ids' appends the
-            # ID to this letter, so 1 character long is not guaranteed)
-            msg_type = msg[0][0]
-
-            if (self.msg_type_dict.get(msg_type)()):
+            if (self.msg_type_dict.get(msg.C)()):
                 self.visible_msgs.append(msg)
                 msg_str = convert_to_string(msg)
                 self.lbMessages.insert(END, msg_str)
@@ -361,12 +356,8 @@ class LintGui(object):
                 #adding message to list of msgs
                 self.msgs.append(msg)
 
-                # Obtaining message type (pylint's '--include-ids' appends the
-                # ID to this letter, so 1 character long is not guaranteed)
-                msg_type = msg[0][0]
-
                 #displaying msg if message type is selected in check box
-                if (self.msg_type_dict.get(msg_type)()):
+                if (self.msg_type_dict.get(msg.C)()):
                     self.visible_msgs.append(msg)
                     msg_str = convert_to_string(msg)
                     self.lbMessages.insert(END, msg_str)
@@ -478,18 +469,15 @@ class LintGui(object):
             return
 
         msg = self.visible_msgs[int(selected[0])]
-        filename = msg[2]
-        fileline = int(msg[5])
-
-        scroll = fileline - 3
+        scroll = msg.line - 3
         if scroll < 0:
             scroll = 0
 
-        self.tabs["Source File"] = open(filename, "r").readlines()
+        self.tabs["Source File"] = open(msg.path, "r").readlines()
         self.box.set("Source File")
         self.refresh_results_window()
         self.results.yview(scroll)
-        self.results.select_set(fileline - 1)
+        self.results.select_set(msg.line - 1)
 
 
 def lint_thread(module, reporter, gui):
diff --git a/lint.py b/lint.py
index a039bae..e5e89e5 100644
--- a/lint.py
+++ b/lint.py
@@ -262,7 +262,7 @@ This is used by the global evaluation report (RP0004).'}),
                   'group': 'Reports',
                   'help' : ('Template used to display messages. '
                             'This is a python new-style format string '
-                            'used to format the massage information. '
+                            'used to format the message information. '
                             'See doc for all details')
                   }), # msg-template
                )
diff --git a/reporters/guireporter.py b/reporters/guireporter.py
index 9f3ae79..331eb17 100644
--- a/reporters/guireporter.py
+++ b/reporters/guireporter.py
@@ -3,7 +3,7 @@
 import sys
 
 from pylint.interfaces import IReporter
-from pylint.reporters import BaseReporter
+from pylint.reporters import BaseReporter, Message
 from logilab.common.ureports import TextWriter
 
 
@@ -16,16 +16,12 @@ class GUIReporter(BaseReporter):
     def __init__(self, gui, output=sys.stdout):
         """init"""
         BaseReporter.__init__(self, output)
-        self.msgs = []
         self.gui = gui
 
     def add_message(self, msg_id, location, msg):
         """manage message of different type and in the context of path"""
-        filename, module, obj, line, col_offset = location
-        msg = Message(self, msg_id, location, msg)
-        full_msg = [msg.C, msg_id, filename, module, obj, str(line), msg]
-        self.msgs += [[sigle, module, obj, str(line)]]
-        self.gui.msg_queue.put(full_msg)
+        message = Message(self, msg_id, location, msg)
+        self.gui.msg_queue.put(message)
 
     def _display(self, layout):
         """launch layouts display"""
diff --git a/test/input/func_non_iterator_returned_py30.py b/test/input/func_non_iterator_returned_py30.py
new file mode 100644
index 0000000..6915768
--- /dev/null
+++ b/test/input/func_non_iterator_returned_py30.py
@@ -0,0 +1,52 @@
+"""Check non-iterators returned by __iter__ """
+
+# pylint: disable=too-few-public-methods
+
+__revision__ = 0
+
+class FirstGoodIterator(object):
+    """ yields in iterator. """
+
+    def __iter__(self):
+        for index in range(10):
+            yield index
+
+class SecondGoodIterator(object):
+    """ __iter__ and next """
+
+    def __iter__(self):
+        return self
+
+    def __next__(self): # pylint: disable=no-self-use
+        """ Infinite iterator, but still an iterator """
+        return 1
+
+class ThirdGoodIterator(object):
+    """ Returns other iterator, not the current instance """
+
+    def __iter__(self):
+        return SecondGoodIterator()
+
+class FourthGoodIterator(object):
+    """ __iter__ returns iter(...) """
+
+    def __iter__(self):
+        return iter(range(10))
+
+class FirstBadIterator(object):
+    """ __iter__ returns a list """
+
+    def __iter__(self):
+        return []
+
+class SecondBadIterator(object):
+    """ __iter__ without next """
+
+    def __iter__(self):
+        return self
+
+class ThirdBadIterator(object):
+    """ __iter__ returns an instance of another non-iterator """
+
+    def __iter__(self):
+        return SecondBadIterator()
diff --git a/test/input/func_non_iterator_returned_py_30.py b/test/input/func_non_iterator_returned_py_30.py
new file mode 100644
index 0000000..ff75941
--- /dev/null
+++ b/test/input/func_non_iterator_returned_py_30.py
@@ -0,0 +1,52 @@
+"""Check non-iterators returned by __iter__ """
+
+# pylint: disable=too-few-public-methods
+
+__revision__ = 0
+
+class FirstGoodIterator(object):
+    """ yields in iterator. """
+
+    def __iter__(self):
+        for index in range(10):
+            yield index
+
+class SecondGoodIterator(object):
+    """ __iter__ and next """
+
+    def __iter__(self):
+        return self
+
+    def next(self): # pylint: disable=no-self-use
+        """ Infinite iterator, but still an iterator """
+        return 1
+
+class ThirdGoodIterator(object):
+    """ Returns other iterator, not the current instance """
+
+    def __iter__(self):
+        return SecondGoodIterator()
+
+class FourthGoodIterator(object):
+    """ __iter__ returns iter(...) """
+
+    def __iter__(self):
+        return iter(range(10))
+
+class FirstBadIterator(object):
+    """ __iter__ returns a list """
+
+    def __iter__(self):
+        return []
+
+class SecondBadIterator(object):
+    """ __iter__ without next """
+
+    def __iter__(self):
+        return self
+
+class ThirdBadIterator(object):
+    """ __iter__ returns an instance of another non-iterator """
+
+    def __iter__(self):
+        return SecondBadIterator()
diff --git a/test/input/func_useless_else_on_loop.py b/test/input/func_useless_else_on_loop.py
index 79be8e6..cec5a74 100644
--- a/test/input/func_useless_else_on_loop.py
+++ b/test/input/func_useless_else_on_loop.py
@@ -3,7 +3,7 @@
 __revision__ = 0
 
 def test_return_for():
-    """else + return is accetable."""
+    """else + return is not accetable."""
     for i in range(10):
         if i % 2:
             return i
@@ -11,7 +11,7 @@ def test_return_for():
         print 'math is broken'
 
 def test_return_while():
-    """else + return is accetable."""
+    """else + return is not accetable."""
     while True:
         return 1
     else:
diff --git a/test/messages/func_non_iterator_returned_py30.txt b/test/messages/func_non_iterator_returned_py30.txt
new file mode 100644
index 0000000..b41b14b
--- /dev/null
+++ b/test/messages/func_non_iterator_returned_py30.txt
@@ -0,0 +1,3 @@
+W: 39:FirstBadIterator.__iter__: __iter__ returns non-iterator
+W: 45:SecondBadIterator.__iter__: __iter__ returns non-iterator
+W: 51:ThirdBadIterator.__iter__: __iter__ returns non-iterator
\ No newline at end of file
diff --git a/test/messages/func_non_iterator_returned_py_30.txt b/test/messages/func_non_iterator_returned_py_30.txt
new file mode 100644
index 0000000..b41b14b
--- /dev/null
+++ b/test/messages/func_non_iterator_returned_py_30.txt
@@ -0,0 +1,3 @@
+W: 39:FirstBadIterator.__iter__: __iter__ returns non-iterator
+W: 45:SecondBadIterator.__iter__: __iter__ returns non-iterator
+W: 51:ThirdBadIterator.__iter__: __iter__ returns non-iterator
\ No newline at end of file
diff --git a/test/unittest_lint.py b/test/unittest_lint.py
index a65eb01..0b847c2 100644
--- a/test/unittest_lint.py
+++ b/test/unittest_lint.py
@@ -26,22 +26,12 @@ from logilab.common.compat import reload
 from pylint import config
 from pylint.lint import PyLinter, Run, UnknownMessage, preprocess_options, \
      ArgumentPreprocessingError
-from pylint.utils import sort_msgs, PyLintASTWalker, MSG_STATE_SCOPE_CONFIG, \
-     MSG_STATE_SCOPE_MODULE, tokenize_module
+from pylint.utils import MSG_STATE_SCOPE_CONFIG, MSG_STATE_SCOPE_MODULE, \
+    PyLintASTWalker, MessageDefinition, build_message_def, tokenize_module
 from pylint.testutils import TestReporter
 from pylint.reporters import text
 from pylint import checkers
 
-class SortMessagesTC(TestCase):
-
-    def test(self):
-        l = ['E0501', 'E0503', 'F0002', 'I0201', 'W0540',
-             'R0202', 'F0203', 'R0220', 'W0321', 'I0001']
-        self.assertEqual(sort_msgs(l), ['E0501', 'E0503',
-                                         'W0321', 'W0540',
-                                         'R0202', 'R0220',
-                                         'I0001', 'I0201',
-                                         'F0002', 'F0203',])
 
 class GetNoteMessageTC(TestCase):
     def test(self):
@@ -83,11 +73,40 @@ class PyLinterTC(TestCase):
         checkers.initialize(self.linter)
         self.linter.set_reporter(TestReporter())
 
+    def test_check_message_id(self):
+        self.assertIsInstance(self.linter.check_message_id('F0001'),
+                              MessageDefinition)
+        self.assertRaises(UnknownMessage,
+                          self.linter.check_message_id, 'YB12')
+
     def test_message_help(self):
-        msg = self.linter.get_message_help('F0001', checkerref=True)
-        expected = ':F0001 (fatal):\n  Used when an error occurred preventing the analysis of a module (unable to\n  find it for instance). This message belongs to the master checker.'
-        self.assertMultiLineEqual(msg, expected)
-        self.assertRaises(UnknownMessage, self.linter.get_message_help, 'YB12')
+        msg = self.linter.check_message_id('F0001')
+        self.assertMultiLineEqual(
+            ''':F0001 (fatal):
+  Used when an error occurred preventing the analysis of a module (unable to
+  find it for instance). This message belongs to the master checker.''',
+            msg.format_help(checkerref=True))
+        self.assertMultiLineEqual(
+            ''':F0001 (fatal):
+  Used when an error occurred preventing the analysis of a module (unable to
+  find it for instance).''',
+            msg.format_help(checkerref=False))
+
+    def test_message_help_minmax(self):
+        # build the message manually to be python version independant
+        msg = build_message_def(self.linter._checkers['typecheck'][0],
+                                'E1122', checkers.typecheck.MSGS['E1122'])
+        self.assertMultiLineEqual(
+            ''':E1122 (duplicate-keyword-arg): *Duplicate keyword argument %r in function call*
+  Used when a function call passes the same keyword argument multiple times.
+  This message belongs to the typecheck checker. It can't be emitted when using
+  Python >= 2.6.''',
+            msg.format_help(checkerref=True))
+        self.assertMultiLineEqual(
+            ''':E1122 (duplicate-keyword-arg): *Duplicate keyword argument %r in function call*
+  Used when a function call passes the same keyword argument multiple times.
+  This message can't be emitted when using Python >= 2.6.''',
+            msg.format_help(checkerref=False))
 
     def test_enable_message(self):
         linter = self.linter
diff --git a/test/unittest_reporting.py b/test/unittest_reporting.py
index d338670..8fda31d 100644
--- a/test/unittest_reporting.py
+++ b/test/unittest_reporting.py
@@ -1,4 +1,4 @@
-# Copyright (c) 2003-2012 LOGILAB S.A. (Paris, FRANCE).
+# Copyright (c) 2003-2013 LOGILAB S.A. (Paris, FRANCE).
 # This program 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 2 of the License, or (at your option) any later
@@ -12,23 +12,13 @@
 # this program; if not, write to the Free Software Foundation, Inc.,
 # 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 
-import sys
 import os
-import tempfile
-from shutil import rmtree
-from os import getcwd, chdir
-from os.path import join, basename, dirname, isdir, abspath
+from os.path import join, dirname, abspath
 from cStringIO import StringIO
 
-from logilab.common.testlib import TestCase, unittest_main, create_files
-from logilab.common.compat import reload
+from logilab.common.testlib import TestCase, unittest_main
 
-from pylint import config
-from pylint.lint import PyLinter, Run, UnknownMessage, preprocess_options, \
-     ArgumentPreprocessingError
-from pylint.utils import sort_msgs, PyLintASTWalker, MSG_STATE_SCOPE_CONFIG, \
-     MSG_STATE_SCOPE_MODULE, tokenize_module
-from pylint.testutils import TestReporter
+from pylint.lint import PyLinter
 from pylint import checkers
 from pylint.reporters.text import TextReporter
 
@@ -46,12 +36,6 @@ class PyLinterTC(TestCase):
         os.environ.pop('PYLINTRC', None)
 
     def test_template_option(self):
-        # self.linter.set_reporter(TextReporter())
-        expected = ( '************* Module 0123\n'
-                     'C0301:001\n'
-                     'C0301:002\n'
-                     )
-
         output = StringIO()
         self.linter.reporter.set_output(output)
         self.linter.set_option('msg-template', '{msg_id}:{line:03d}')
@@ -59,7 +43,10 @@ class PyLinterTC(TestCase):
         self.linter.set_current_module('0123')
         self.linter.add_message('C0301', line=1, args=(1, 2))
         self.linter.add_message('line-too-long', line=2, args=(3, 4))
-        self.assertMultiLineEqual(output.getvalue(), expected)
+        self.assertMultiLineEqual(output.getvalue(),
+                                  '************* Module 0123\n'
+                                  'C0301:001\n'
+                                  'C0301:002\n')
 
 
 if __name__ == '__main__':
diff --git a/utils.py b/utils.py
index 1895a75..3dc8410 100644
--- a/utils.py
+++ b/utils.py
@@ -20,8 +20,8 @@ main pylint class
 import re
 import sys
 import tokenize
-from warnings import warn
 import os
+from warnings import warn
 from os.path import dirname, basename, splitext, exists, isdir, join, normpath
 
 from logilab.common.interface import implements
@@ -43,7 +43,6 @@ class EmptyReport(Exception):
     """raised when a report is empty and so should not be displayed"""
 
 
-
 MSG_TYPES = {
     'I' : 'info',
     'C' : 'convention',
@@ -77,17 +76,6 @@ class WarningScope(object):
     NODE = 'node-based-msg'
 
 
-def sort_msgs(msgids):
-    """sort message identifiers according to their category first"""
-    msgs = {}
-    for msg in msgids:
-        msgs.setdefault(msg[0], []).append(msg)
-    result = []
-    for m_id in _MSG_ORDER:
-        if m_id in msgs:
-            result.extend( sorted(msgs[m_id]) )
-    return result
-
 def get_module_and_frameid(node):
     """return the module name and the frame id in the module"""
     frame = node.frame()
@@ -122,18 +110,78 @@ def tokenize_module(module):
         return list(tokenize.generate_tokens(readline))
     return list(tokenize.tokenize(readline))
 
+def build_message_def(checker, msgid, msg_tuple):
+    if implements(checker, (IRawChecker, ITokenChecker)):
+        default_scope = WarningScope.LINE
+    else:
+        default_scope = WarningScope.NODE
+    options = {}
+    if len(msg_tuple) > 3:
+        (msg, symbol, descr, options) = msg_tuple
+    elif len(msg_tuple) > 2:
+        (msg, symbol, descr) = msg_tuple[:3]
+    else:
+        # messages should have a symbol, but for backward compatibility
+        # they may not.
+        (msg, descr) = msg_tuple
+        warn("[pylint 0.26] description of message %s doesn't include "
+             "a symbolic name" % msgid, DeprecationWarning)
+        symbol = None
+    options.setdefault('scope', default_scope)
+    return MessageDefinition(checker, msgid, msg, descr, symbol, **options)
+
 
 class MessageDefinition(object):
-    def __init__(self, checker, msgid, msg, descr, symbol, scope):
+    def __init__(self, checker, msgid, msg, descr, symbol, scope,
+                 minversion=None, maxversion=None):
+        self.checker = checker
         assert len(msgid) == 5, 'Invalid message id %s' % msgid
         assert msgid[0] in MSG_TYPES, \
                'Bad message type %s in %r' % (msgid[0], msgid)
         self.msgid = msgid
         self.msg = msg
         self.descr = descr
-        self.checker = checker
         self.symbol = symbol
         self.scope = scope
+        self.minversion = minversion
+        self.maxversion = maxversion
+
+    def may_be_emitted(self):
+        """return True if message may be emitted using the current interpreter"""
+        if self.minversion is not None and self.minversion > sys.version_info:
+            return False
+        if self.maxversion is not None and self.maxversion <= sys.version_info:
+            return False
+        return True
+
+    def format_help(self, checkerref=False):
+        """return the help string for the given message id"""
+        desc = self.descr
+        if checkerref:
+            desc += ' This message belongs to the %s checker.' % \
+                   self.checker.name
+        title = self.msg
+        if self.symbol:
+            symbol_part = ' (%s)' % self.symbol
+        else:
+            symbol_part = ''
+        if self.minversion or self.maxversion:
+            restr = []
+            if self.minversion:
+                restr.append('< %s' % '.'.join([str(n) for n in self.minversion]))
+            if self.maxversion:
+                restr.append('>= %s' % '.'.join([str(n) for n in self.maxversion]))
+            restr = ' or '.join(restr)
+            if checkerref:
+                desc += " It can't be emitted when using Python %s." % restr
+            else:
+                desc += " This message can't be emitted when using Python %s." % restr
+        desc = normalize_text(' '.join(desc.split()), indent='  ')
+        if title != '%s':
+            title = title.splitlines()[0]
+            return ':%s%s: *%s*\n%s' % (self.msgid, symbol_part, title, desc)
+        return ':%s%s:\n%s' % (self.msgid, symbol_part, desc)
+
 
 class MessagesHandlerMixIn(object):
     """a mix-in class containing all the messages related methods for the main
@@ -162,65 +210,23 @@ class MessagesHandlerMixIn(object):
         message ids should be a string of len 4, where the two first characters
         are the checker id and the two last the message id in this checker
         """
-        msgs_dict = checker.msgs
         chkid = None
-
-        for msgid, msg_tuple in msgs_dict.iteritems():
-            if implements(checker, (IRawChecker, ITokenChecker)):
-                scope = WarningScope.LINE
-            else:
-                scope = WarningScope.NODE
-            if len(msg_tuple) > 2:
-                (msg, msgsymbol, msgdescr) = msg_tuple[:3]
-                assert msgsymbol not in self._messages_by_symbol, \
-                    'Message symbol %r is already defined' % msgsymbol
-                if len(msg_tuple) > 3:
-                    if 'scope' in msg_tuple[3]:
-                        scope = msg_tuple[3]['scope']
-                    if 'minversion' in msg_tuple[3]:
-                        minversion = msg_tuple[3]['minversion']
-                        if minversion > sys.version_info:
-                            self._msgs_state[msgid] = False
-                            continue
-                    if 'maxversion' in msg_tuple[3]:
-                        maxversion = msg_tuple[3]['maxversion']
-                        if maxversion <= sys.version_info:
-                            self._msgs_state[msgid] = False
-                            continue
-            else:
-                # messages should have a symbol, but for backward compatibility
-                # they may not.
-                (msg, msgdescr) = msg_tuple
-                warn("[pylint 0.26] description of message %s doesn't include "
-                     "a symbolic name" % msgid, DeprecationWarning)
-                msgsymbol = None
+        for msgid, msg_tuple in checker.msgs.iteritems():
+            msg = build_message_def(checker, msgid, msg_tuple)
+            assert msg.symbol not in self._messages_by_symbol, \
+                    'Message symbol %r is already defined' % msg.symbol
             # avoid duplicate / malformed ids
-            assert msgid not in self._messages, \
+            assert msg.msgid not in self._messages, \
                    'Message id %r is already defined' % msgid
-            assert chkid is None or chkid == msgid[1:3], \
+            assert chkid is None or chkid == msg.msgid[1:3], \
                    'Inconsistent checker part in message id %r' % msgid
-            chkid = msgid[1:3]
-            msg = MessageDefinition(checker, msgid, msg, msgdescr, msgsymbol, scope)
-            self._messages[msgid] = msg
-            self._messages_by_symbol[msgsymbol] = msg
-            self._msgs_by_category.setdefault(msgid[0], []).append(msgid)
-
-    def get_message_help(self, msgid, checkerref=False):
-        """return the help string for the given message id"""
-        msg = self.check_message_id(msgid)
-        desc = normalize_text(' '.join(msg.descr.split()), indent='  ')
-        if checkerref:
-            desc += ' This message belongs to the %s checker.' % \
-                   msg.checker.name
-        title = msg.msg
-        if msg.symbol:
-            symbol_part = ' (%s)' % msg.symbol
-        else:
-            symbol_part = ''
-        if title != '%s':
-            title = title.splitlines()[0]
-            return ':%s%s: *%s*\n%s' % (msg.msgid, symbol_part, title, desc)
-        return ':%s%s:\n%s' % (msg.msgid, symbol_part, desc)
+            chkid = msg.msgid[1:3]
+            if not msg.may_be_emitted():
+                self._msgs_state[msg.msgid] = False
+                continue
+            self._messages[msg.msgid] = msg
+            self._messages_by_symbol[msg.symbol] = msg
+            self._msgs_by_category.setdefault(msg.msgid[0], []).append(msg.msgid)
 
     def disable(self, msgid, scope='package', line=None):
         """don't output message of the given id"""
@@ -417,7 +423,7 @@ class MessagesHandlerMixIn(object):
         """display help messages for the given message identifiers"""
         for msgid in msgids:
             try:
-                print self.get_message_help(msgid, True)
+                print self.check_message_id(msgid).format_help(checkerref=True)
                 print
             except UnknownMessage, ex:
                 print ex
@@ -467,8 +473,10 @@ class MessagesHandlerMixIn(object):
                 title = ('%smessages' % prefix).capitalize()
                 print title
                 print '~' * len(title)
-                for msgid in sort_msgs(msgs.iterkeys()):
-                    print self.get_message_help(msgid, False)
+                for msgid, msg in sorted(msgs.iteritems(),
+                                         key=lambda (k,v): (_MSG_ORDER.index(k[0]), k)):
+                    msg = build_message_def(checker, msgid, msg)
+                    print msg.format_help(checkerref=False)
                 print
             if reports:
                 title = ('%sreports' % prefix).capitalize()
@@ -486,7 +494,7 @@ class MessagesHandlerMixIn(object):
             msgids.append(msgid)
         msgids.sort()
         for msgid in msgids:
-            print self.get_message_help(msgid, False)
+            print self.check_message_id(msgid).format_help(checkerref=False)
         print