Look all the methods from ancestors for too-few-public-methods.

This patch uses two counters for too-few-public-methods and too-many-public-methods.
In order to avoid false positives, too-many-public-methods check is looking
only for methods defined in the current class. On the other hand, too-few-public-methods
should look in ancestors as well, since most of the time this check is useful only
for simple classes, without many public methods.
Closes issue #471.

3 files changed, 40 insertions, 14 deletions

diff --git a/ChangeLog b/ChangeLog
index c51942d..4c93046 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -10,6 +10,9 @@ ChangeLog for Pylint
       an attribute access ('{0.__class__}').
       Closes issue #463.
 
+    * Take in account all the methods from the ancestors
+      when checking for too-few-public-methods. Closes issue #471.
+
 
 2015-01-16 -- 1.4.1
 
diff --git a/checkers/design_analysis.py b/checkers/design_analysis.py
index 0a7a307..e361cca 100644
--- a/checkers/design_analysis.py
+++ b/checkers/design_analysis.py
@@ -234,28 +234,35 @@ class MisdesignChecker(BaseChecker):
             except KeyError:
                 self._used_abstracts[parent] = 1
 
-    @check_messages('too-many-ancestors', 'too-many-instance-attributes',
-                    'too-few-public-methods', 'too-many-public-methods',
-                    'abstract-class-not-used', 'abstract-class-little-used',
-                    'interface-not-implemented')
+    @check_messages('too-few-public-methods', 'too-many-public-methods')
     def leave_class(self, node):
         """check number of public methods"""
-        nb_public_methods = 0
-        for method in node.mymethods():
-            if not method.name.startswith('_'):
-                nb_public_methods += 1
-        # Does the class contain less than 20 public methods ?
-        if nb_public_methods > self.config.max_public_methods:
+        my_methods = sum(1 for method in node.mymethods()
+                         if not method.name.startswith('_'))
+        all_methods = sum(1 for method in node.methods()
+                          if not method.name.startswith('_'))
+
+        # Does the class contain less than n public methods ?
+        # This checks only the methods defined in the current class,
+        # since the user might not have control over the classes
+        # from the ancestors. It avoids some false positives
+        # for classes such as unittest.TestCase, which provides
+        # a lot of assert methods. It doesn't make sense to warn
+        # when the user subclasses TestCase to add his own tests.
+        if my_methods > self.config.max_public_methods:
             self.add_message('too-many-public-methods', node=node,
-                             args=(nb_public_methods,
+                             args=(my_methods,
                                    self.config.max_public_methods))
         # stop here for exception, metaclass and interface classes
         if node.type != 'class':
             return
-        # Does the class contain more than 5 public methods ?
-        if nb_public_methods < self.config.min_public_methods:
+
+        # Does the class contain more than n public methods ?
+        # This checks all the methods defined by ancestors and
+        # by the current class.
+        if all_methods < self.config.min_public_methods:
             self.add_message('too-few-public-methods', node=node,
-                             args=(nb_public_methods,
+                             args=(all_methods,
                                    self.config.min_public_methods))
 
     @check_messages('too-many-return-statements', 'too-many-branches',
diff --git a/test/input/func_r0903.py b/test/input/func_r0903.py
index 917b0ea..49008f9 100644
--- a/test/input/func_r0903.py
+++ b/test/input/func_r0903.py
@@ -12,3 +12,19 @@ class Aaaa(object):
     def _dontcount(self):
         """not public"""
         print(self)
+
+
+# Don't emit for these cases.
+class Klass(object):
+    """docstring"""
+
+    def meth1(self):
+        """first"""
+
+    def meth2(self):
+        """second"""
+
+
+class EnoughPublicMethods(Klass):
+    """We shouldn't emit too-few-public-methods for this."""
+