Add confidence to error messages about `str.translate` and `str.encode/decode` (#1197)

3 files changed, 45 insertions, 16 deletions

diff --git a/pylint/checkers/python3.py b/pylint/checkers/python3.py
index 2b91e82d6..e2c6f12e2 100644
--- a/pylint/checkers/python3.py
+++ b/pylint/checkers/python3.py
@@ -16,6 +16,7 @@ import astroid
 from astroid import bases
 
 from pylint import checkers, interfaces
+from pylint.interfaces import INFERENCE_FAILURE, INFERENCE
 from pylint.utils import WarningScope
 from pylint.checkers import utils
 
@@ -614,12 +615,14 @@ class Python3Checker(checkers.BaseChecker):
 
     @staticmethod
     def _could_be_string(inferred_types):
+        confidence = INFERENCE if inferred_types else INFERENCE_FAILURE
         for inferred_type in inferred_types:
-            if not (inferred_type == astroid.Uninferable or (
-                    isinstance(inferred_type, astroid.Const) and
-                    isinstance(inferred_type.value, six.string_types))):
-                return False
-        return True
+            if inferred_type is astroid.Uninferable:
+                confidence = INFERENCE_FAILURE
+            elif not (isinstance(inferred_type, astroid.Const) and
+                      isinstance(inferred_type.value, six.string_types)):
+                return None
+        return confidence
 
     def visit_call(self, node):
         self._check_cmp_argument(node)
@@ -628,14 +631,15 @@ class Python3Checker(checkers.BaseChecker):
             inferred_types = set()
             try:
                 for inferred_receiver in node.func.expr.infer():
-                    inferred_types.add(type(inferred_receiver))
+                    inferred_types.add(inferred_receiver)
                     if isinstance(inferred_receiver, astroid.Module):
                         self._warn_if_deprecated(node, inferred_receiver.name,
                                                  {node.func.attrname})
             except astroid.InferenceError:
                 pass
             if node.args:
-                if self._could_be_string(inferred_types):
+                is_str_confidence = self._could_be_string(inferred_types)
+                if is_str_confidence:
                     if (node.func.attrname in ('encode', 'decode') and
                             len(node.args) >= 1 and node.args[0]):
                         first_arg = node.args[0]
@@ -656,7 +660,9 @@ class Python3Checker(checkers.BaseChecker):
                         # after checking several large codebases it did not have any false
                         # positives while finding several real issues.  This call pattern seems
                         # rare enough that the trade off is worth it.
-                        self.add_message('deprecated-str-translate-call', node=node)
+                        self.add_message('deprecated-str-translate-call',
+                                         node=node,
+                                         confidence=is_str_confidence)
                 return
             if node.keywords:
                 return
diff --git a/pylint/test/unittest_checker_python3.py b/pylint/test/unittest_checker_python3.py
index 28a6d8052..165d9dad0 100644
--- a/pylint/test/unittest_checker_python3.py
+++ b/pylint/test/unittest_checker_python3.py
@@ -15,6 +15,7 @@ import astroid
 
 from pylint import testutils
 from pylint.checkers import python3 as checker
+from pylint.interfaces import INFERENCE_FAILURE, INFERENCE
 
 
 def python2_only(test):
@@ -652,16 +653,30 @@ class Python3CheckerTest(testutils.CheckerTestCase):
         node = astroid.extract_node('''
          foobar.translate(None, 'abc123') #@
          ''')
-        message = testutils.Message('deprecated-str-translate-call', node=node)
+        message = testutils.Message('deprecated-str-translate-call', node=node,
+                                    confidence=INFERENCE_FAILURE)
         with self.assertAddsMessages(message):
             self.checker.visit_call(node)
 
     @python2_only
     def test_bad_str_translate_call_variable(self):
         node = astroid.extract_node('''
+         def raz(foobar):
+           foobar.translate(None, 'hello') #@
+         ''')
+        message = testutils.Message('deprecated-str-translate-call', node=node,
+                                    confidence=INFERENCE_FAILURE)
+        with self.assertAddsMessages(message):
+            self.checker.visit_call(node)
+
+    @python2_only
+    def test_bad_str_translate_call_infer_str(self):
+        node = astroid.extract_node('''
+         foobar = "hello world"
          foobar.translate(None, foobar) #@
          ''')
-        message = testutils.Message('deprecated-str-translate-call', node=node)
+        message = testutils.Message('deprecated-str-translate-call', node=node,
+                                    confidence=INFERENCE)
         with self.assertAddsMessages(message):
             self.checker.visit_call(node)
 
diff --git a/pylint/testutils.py b/pylint/testutils.py
index 892ca7c73..c6bd0a7a2 100644
--- a/pylint/testutils.py
+++ b/pylint/testutils.py
@@ -132,9 +132,18 @@ class TestReporter(BaseReporter):
 
 
 class Message(collections.namedtuple('Message',
-                                     ['msg_id', 'line', 'node', 'args'])):
-    def __new__(cls, msg_id, line=None, node=None, args=None):
-        return tuple.__new__(cls, (msg_id, line, node, args))
+                                     ['msg_id', 'line', 'node', 'args', 'confidence'])):
+    def __new__(cls, msg_id, line=None, node=None, args=None, confidence=None):
+        return tuple.__new__(cls, (msg_id, line, node, args, confidence))
+
+    def __eq__(self, other):
+        if isinstance(other, Message):
+            if self.confidence and other.confidence:
+                return super(Message, self).__eq__(other)
+            return self[:-1] == other[:-1]
+        return NotImplemented  # pragma: no cover
+
+    __hash__ = None
 
 
 class UnittestLinter(object):
@@ -151,9 +160,8 @@ class UnittestLinter(object):
         finally:
             self._messages = []
 
-    def add_message(self, msg_id, line=None, node=None, args=None,
-                    confidence=None):
-        self._messages.append(Message(msg_id, line, node, args))
+    def add_message(self, msg_id, line=None, node=None, args=None, confidence=None):
+        self._messages.append(Message(msg_id, line, node, args, confidence))
 
     def is_message_enabled(self, *unused_args, **unused_kwargs):
         return True