Add string_format pylint plugin.

test/sanity/pylint/plugins/string_format.py

@@ -0,0 +1,86 @@
+# (c) 2018, Matt Martz <matt@sivel.net>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+# -*- coding: utf-8 -*-
+from __future__ import (absolute_import, division, print_function)
+__metaclass__ = type
+
+import sys
+
+import six
+
+import astroid
+from pylint.interfaces import IAstroidChecker
+from pylint.checkers import BaseChecker
+from pylint.checkers import utils
+from pylint.checkers.utils import check_messages
+from pylint.checkers.strings import parse_format_method_string
+
+_PY3K = sys.version_info[:2] >= (3, 0)
+
+MSGS = {
+    'E9305': ("Format string contains automatic field numbering "
+              "specification",
+              "ansible-format-automatic-specification",
+              "Used when a PEP 3101 format string contains automatic "
+              "field numbering (e.g. '{}').",
+              {'minversion': (2, 6)}),
+    'E9390': ("bytes object has no .format attribute",
+              "ansible-no-format-on-bytestring",
+              "Used when a bytestring was used as a PEP 3101 format string "
+              "as Python3 bytestrings do not have a .format attribute",
+              {'minversion': (3, 0)}),
+}
+
+
+class AnsibleStringFormatChecker(BaseChecker):
+    """Checks string formatting operations to ensure that the format string
+    is valid and the arguments match the format string.
+    """
+
+    __implements__ = (IAstroidChecker,)
+    name = 'string'
+    msgs = MSGS
+
+    @check_messages(*(MSGS.keys()))
+    def visit_call(self, node):
+        func = utils.safe_infer(node.func)
+        if (isinstance(func, astroid.BoundMethod)
+                and isinstance(func.bound, astroid.Instance)
+                and func.bound.name in ('str', 'unicode', 'bytes')):
+            if func.name == 'format':
+                self._check_new_format(node, func)
+
+    def _check_new_format(self, node, func):
+        """ Check the new string formatting """
+        if (isinstance(node.func, astroid.Attribute)
+                and not isinstance(node.func.expr, astroid.Const)):
+            return
+        try:
+            strnode = next(func.bound.infer())
+        except astroid.InferenceError:
+            return
+        if not isinstance(strnode, astroid.Const):
+            return
+
+        if _PY3K and isinstance(strnode.value, six.binary_type):
+            self.add_message('ansible-no-format-on-bytestring', node=node)
+            return
+        if not isinstance(strnode.value, six.string_types):
+            return
+
+        if node.starargs or node.kwargs:
+            return
+        try:
+            fields, num_args, manual_pos = parse_format_method_string(strnode.value)
+        except utils.IncompleteFormatString:
+            return
+
+        if num_args:
+            self.add_message('ansible-format-automatic-specification',
+                             node=node)
+            return
+
+
+def register(linter):
+    """required method to auto register this checker """
+    linter.register_checker(AnsibleStringFormatChecker(linter))