[anaconda:master 2/3] Add a simple pointless-override checker to pylint checkers.
mulhern
amulhern at redhat.com
Tue Dec 2 18:24:20 UTC 2014
Call it in pylint-one.sh.
Signed-off-by: mulhern <amulhern at redhat.com>
---
tests/pylint/pointless-override.py | 252 +++++++++++++++++++++++++++++++++++++
tests/pylint/pylint-one.sh | 2 +-
2 files changed, 253 insertions(+), 1 deletion(-)
create mode 100644 tests/pylint/pointless-override.py
diff --git a/tests/pylint/pointless-override.py b/tests/pylint/pointless-override.py
new file mode 100644
index 0000000..c8d4776
--- /dev/null
+++ b/tests/pylint/pointless-override.py
@@ -0,0 +1,252 @@
+# Pylint checker for pointless class attributes overrides.
+#
+# Copyright (C) 2014 Red Hat, Inc.
+#
+# This copyrighted material is made available to anyone wishing to use,
+# modify, copy, or redistribute it subject to the terms and conditions of
+# the GNU General Public License v.2, or (at your option) any later version.
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY expressed or implied, including the implied warranties 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 this program; if not, write to the
+# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301, USA. Any Red Hat trademarks that are incorporated in the
+# source code or documentation are not subject to the GNU General Public
+# License and may only be used or replicated with the express permission of
+# Red Hat, Inc.
+#
+# Red Hat Author(s): Anne Mulhern <amulhern at redhat.com>
+#
+
+import abc
+
+from six import add_metaclass
+
+import astroid
+
+from pylint.checkers import BaseChecker
+from pylint.checkers.utils import check_messages
+from pylint.interfaces import IAstroidChecker
+
+ at add_metaclass(abc.ABCMeta)
+class PointlessData(object):
+
+ _DEF_CLASS = abc.abstractproperty(doc="Class of interesting definitions.")
+ message_id = abc.abstractproperty(doc="Pylint message identifier.")
+
+ @classmethod
+ @abc.abstractmethod
+ def _retain_node(cls, node, restrict=True):
+ """ Determines whether to retain a node for the analysis.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :param restrict bool: True if results returned should be restricted
+ :returns: True if the node should be kept, otherwise False
+ :rtype: bool
+
+ Restricted nodes are candidates for being marked as overridden.
+ Only restricted nodes are put into the initial pool of candidates.
+ """
+ raise NotImplementedError()
+
+ @staticmethod
+ @abc.abstractmethod
+ def _extract_value(node):
+ """ Return the node that contains the assignment's value.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :returns: the node corresponding to the value
+ :rtype: bool
+ """
+ raise NotImplementedError()
+
+ @staticmethod
+ @abc.abstractmethod
+ def _extract_targets(node):
+ """ Generates the names being assigned to.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :returns: a list of assignment target names
+ :rtype: generator of str
+ """
+ raise NotImplementedError()
+
+ @classmethod
+ def get_data(cls, node, restrict=True):
+ """ Find relevant nodes for this analysis.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :param restrict bool: True if results returned should be restricted
+
+ :rtype: generator of astroid.Class
+ :returns: a generator of interesting nodes.
+
+ Note that all nodes returned are guaranteed to be instances of
+ some class in self._DEF_CLASS.
+ """
+ nodes = (n for n in node.body if isinstance(n, cls._DEF_CLASS))
+ for n in nodes:
+ if cls._retain_node(n, restrict):
+ for name in cls._extract_targets(n):
+ yield (name, cls._extract_value(n))
+
+ @classmethod
+ @abc.abstractmethod
+ def check_equal(cls, node, other):
+ """ Check whether the two nodes are considered equal.
+
+ :param node: some ast node
+ :param other: some ast node
+
+ :rtype: bool
+ :returns: True if the nodes are considered equal, otherwise False
+
+ If the method returns True, the nodes are actually equal, but it
+ may return False when the nodes are equal.
+ """
+ raise NotImplementedError()
+
+class PointlessFunctionDefinition(PointlessData):
+ """ Looking for pointless function definitions. """
+
+ _DEF_CLASS = astroid.Function
+ message_id = "W9952"
+
+ @classmethod
+ def _retain_node(cls, node, restrict=True):
+ return not restrict or \
+ (len(node.body) == 1 and isinstance(node.body[0], astroid.Pass))
+
+ @classmethod
+ def check_equal(cls, node, other):
+ return len(node.body) == 1 and isinstance(node.body[0], astroid.Pass) and \
+ len(other.body) == 1 and isinstance(other.body[0], astroid.Pass)
+
+ @staticmethod
+ def _extract_value(node):
+ return node
+
+ @staticmethod
+ def _extract_targets(node):
+ yield node.name
+
+class PointlessAssignment(PointlessData):
+
+ _DEF_CLASS = astroid.Assign
+ message_id = "W9951"
+
+ _VALUE_CLASSES = (
+ astroid.Const,
+ astroid.Dict,
+ astroid.List,
+ astroid.Tuple
+ )
+
+ @classmethod
+ def _retain_node(cls, node, restrict=True):
+ return not restrict or isinstance(node.value, cls._VALUE_CLASSES)
+
+ @classmethod
+ def check_equal(cls, node, other):
+ if type(node) != type(other):
+ return False
+ if isinstance(node, astroid.Const):
+ return node.value == other.value
+ if isinstance(node, (astroid.List, astroid.Tuple)):
+ return len(node.elts) == len(other.elts) and \
+ all(cls.check_equal(n, o) for (n, o) in zip(node.elts, other.elts))
+ if isinstance(node, astroid.Dict):
+ return len(node.items) == len(other.items)
+ return False
+
+ @staticmethod
+ def _extract_value(node):
+ return node.value
+
+ @staticmethod
+ def _extract_targets(node):
+ for target in node.targets:
+ yield target.name
+
+class PointlessClassAttributeOverrideChecker(BaseChecker):
+ """ If the nearest definition of the class attribute in the MRO assigns
+ it the same value, then the overriding definition is said to be
+ pointless.
+
+ The algorithm for detecting a pointless attribute override is the following.
+
+ * For each class, C:
+ - For each attribute assignment,
+ name_1 = name_2 ... name_n = l (where l is a literal):
+ * For each n in (n_1, n_2):
+ - Traverse the linearization of the MRO until the first
+ matching assignment n = l' is identified. If l is equal to l',
+ then consider that the assignment to l in C is a
+ pointless override.
+
+ The algorithm for detecting a pointless method override has the same
+ general structure, and the same defects discussed below.
+
+ Note that this analysis is neither sound nor complete. It is unsound
+ under multiple inheritance. Consider the following class hierarchy::
+
+ class A(object):
+ _attrib = False
+
+ class B(A):
+ _attrib = False
+
+ class C(A):
+ _attrib = True
+
+ class D(B,C):
+ pass
+
+ In this case, starting from B, B._attrib = False would be considered
+ pointless. However, for D the MRO is B, C, A, and removing the assignment
+ B._attrib = False would change the inherited value of D._attrib from
+ False to True.
+
+ The analysis is incomplete because it will find some values unequal when
+ actually they are equal.
+
+ The analysis is both incomplete and unsound because it expects that
+ assignments will always be made by means of the same syntax.
+ """
+
+ __implements__ = (IAstroidChecker,)
+
+ name = "pointless class attribute override checker"
+ msgs = {
+ "W9951":
+ (
+ "Assignment to class attribute %s overrides identical assignment in ancestor.",
+ "pointless-class-attribute-override",
+ "Assignment to class attribute that overrides assignment in ancestor that assigns identical value has no effect."
+ ),
+ "W9952":
+ (
+ "definition of %s method overrides identical method definition in ancestor",
+ "pointless-method-definition-override",
+ "Overriding empty method definition with another empty method definition has no effect."
+ )
+ }
+
+ @check_messages("W9951", "W9952")
+ def visit_class(self, node):
+ for checker in (PointlessAssignment, PointlessFunctionDefinition):
+ for (name, value) in checker.get_data(node):
+ for a in node.ancestors():
+ match = next((v for (n, v) in checker.get_data(a, False) if n == name), None)
+ if match is not None:
+ if checker.check_equal(value, match):
+ self.add_message(checker.message_id, node=value, args=(name,))
+ break
+
+def register(linter):
+ linter.register_checker(PointlessClassAttributeOverrideChecker(linter))
diff --git a/tests/pylint/pylint-one.sh b/tests/pylint/pylint-one.sh
index 7235674..7c7b8c2 100755
--- a/tests/pylint/pylint-one.sh
+++ b/tests/pylint/pylint-one.sh
@@ -18,7 +18,7 @@ pylint_output="$(pylint \
--dummy-variables-rgx=_ \
--ignored-classes=DefaultInstall,Popen,QueueFactory,TransactionSet \
--defining-attr-methods=__init__,_grabObjects,initialize,reset,start,setUp \
- --load-plugins=intl,preconf,markup,eintr \
+ --load-plugins=intl,preconf,markup,eintr,pointless-override \
--init-hook=\
'import gi.overrides, os;
gi.overrides.__path__[0:0] = (os.environ["ANACONDA_WIDGETS_OVERRIDES"].split(":") if "ANACONDA_WIDGETS_OVERRIDES" in os.environ else [])' \
--
1.9.3
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