[blivet:master 1/2] Add a simple pylint checker for pointless overrides.
mulhern
amulhern at redhat.com
Fri Nov 21 18:07:33 UTC 2014
Invoke it when running pylint.
Signed-off-by: mulhern <amulhern at redhat.com>
---
tests/pylint/pointless-override.py | 194 +++++++++++++++++++++++++++++++++++++
tests/pylint/pylint-one.sh | 2 +-
2 files changed, 195 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..79795ce
--- /dev/null
+++ b/tests/pylint/pointless-override.py
@@ -0,0 +1,194 @@
+# 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 astroid
+
+from pylint.checkers import BaseChecker
+from pylint.checkers.utils import check_messages
+from pylint.interfaces import IAstroidChecker
+
+_VALUE_CLASSES = (
+ astroid.Const,
+ astroid.Dict,
+ astroid.List,
+ astroid.Tuple
+)
+
+def _get_function_definition_data(node, restrict=True):
+ """ Generate name * bool pair for for functions in class.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :param restrict bool: True if results returned should be restricted
+
+ :rtype: generator of str * bool
+ :returns: the name of the function and a representation of the function's
+ definition.
+
+ Returns data for function definitions in the class. The first part is
+ the name, the second part is a Boolean value which is True if the
+ body of the function is a single pass statement, otherwise False.
+ If restrict is True, only returns function definitions where the
+ body is pass.
+ """
+ stmts = (s for s in node.body if isinstance(s, astroid.Function))
+ for stmt in stmts:
+ if len(stmt.body) == 1 and isinstance(stmt.body[0], astroid.Pass):
+ yield (stmt, True)
+ else:
+ if not restrict:
+ yield (stmt, False)
+
+def _get_assignment_data(node, restrict=True):
+ """ Generate target * value pair for subset of interesting
+ assignments in a class.
+
+ :param node: an AST node
+ :type node: astroid.Class
+ :param restrict bool: True if results returned should be restricted
+
+ :rtype: generator of node * node
+ :returns: target and value for interesting assignment statements
+
+ Returns data for all simple statements, i.e., assignments to a single
+ target. If restrict is True, only return assignments where the
+ value has one of the types in _VALUE_CLASSES.
+ """
+ stmts = (s for s in node.body if isinstance(s, astroid.Assign))
+ for stmt in stmts:
+ targets = stmt.targets
+ if len(targets) != 1:
+ continue
+ target = targets[0]
+
+ value = stmt.value
+ if restrict and not isinstance(value, _VALUE_CLASSES):
+ continue
+ yield (target, value)
+
+def _check_equal(node, other):
+ """ Check whether the two nodes have equal values.
+
+ :param node: some ast node
+ :param other: some ast node
+
+ :rtype: bool
+ :returns: True if the nodes have equal values, otherwise False
+
+ Only checks nodes of interest, having types in _VALUE_CLASSES.
+
+ The algorithm is not complete and considers two dicts to be equal
+ only if they are both empty.
+ """
+ if type(node) != type(other):
+ return False
+
+ if not isinstance(node, _VALUE_CLASSES):
+ 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(_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)
+
+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, n = l (where l is a literal):
+ * Traverse the linearization of the MRO until the first 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 deleting 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.
+ """
+
+ __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 (target, value) in _get_assignment_data(node):
+ for a in node.ancestors():
+ match = next((v for (n, v) in _get_assignment_data(a, False) if n.name == target.name), None)
+ if match is not None:
+ if _check_equal(value, match):
+ self.add_message("W9951", node=target, args=(target.name,))
+ break
+
+ for (stmt, value) in _get_function_definition_data(node):
+ for a in node.ancestors():
+ match = next((v for (n, v) in _get_function_definition_data(a, False) if n.name == stmt.name), None)
+ if match is not None:
+ if match == True:
+ self.add_message("W9952", node=stmt, args=(stmt.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 82de490..9b1e79b 100755
--- a/tests/pylint/pylint-one.sh
+++ b/tests/pylint/pylint-one.sh
@@ -16,7 +16,7 @@ pylint_output="$(pylint \
--dummy-variables-rgx=_ \
--ignored-classes=Popen,TransactionSet \
--defining-attr-methods=__init__,_grabObjects,initialize,reset,start,setUp \
- --load-plugins=intl \
+ --load-plugins=intl,pointless-override \
$DISABLED_WARN_OPTIONS \
$DISABLED_ERR_OPTIONS \
$NON_STRICT_OPTIONS "$@" 2>&1 | \
--
1.9.3
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