Pass an inference context to metaclass() when inferring an object type

This should prevent a bunch of recursion errors happening in pylint.
Also refactor the inference of `IfExp` nodes to use separate contexts
for each potential branch.

Close pylint-dev/pylint#3152
Close pylint-dev/pylint#3159

Author: PCManticore

ChangeLog

@@ -14,6 +14,16 @@ Release Date: TBA
   Close PyCQA/pylint#3174
 
 
+* Pass an inference context to `metaclass()` when inferring an object type
+
+  This should prevent a bunch of recursion errors happening in pylint.
+  Also refactor the inference of `IfExp` nodes to use separate contexts
+  for each potential branch.
+
+  Close PyCQA/pylint#3152
+  Close PyCQA/pylint#3159
+
+
 What's New in astroid 2.3.1?
 ============================
 Release Date: 2019-09-30

astroid/helpers.py

@@ -52,7 +52,7 @@ def _object_type(node, context=None):
     for inferred in node.infer(context=context):
         if isinstance(inferred, scoped_nodes.ClassDef):
             if inferred.newstyle:
-                metaclass = inferred.metaclass()
+                metaclass = inferred.metaclass(context=context)
                 if metaclass:
                     yield metaclass
                     continue

astroid/inference.py

@@ -916,21 +916,28 @@ def infer_ifexp(self, context=None):
     depending on the condition.
     """
     both_branches = False
+    # We use two separate contexts for evaluating lhs and rhs because
+    # evaluating lhs may leave some undesired entries in context.path
+    # which may not let us infer right value of rhs.
+
+    context = context or contextmod.InferenceContext()
+    lhs_context = contextmod.copy_context(context)
+    rhs_context = contextmod.copy_context(context)
     try:
-        test = next(self.test.infer(context=context))
+        test = next(self.test.infer(context=context.clone()))
     except exceptions.InferenceError:
         both_branches = True
     else:
         if test is not util.Uninferable:
             if test.bool_value():
-                yield from self.body.infer(context=context)
+                yield from self.body.infer(context=lhs_context)
             else:
-                yield from self.orelse.infer(context=context)
+                yield from self.orelse.infer(context=rhs_context)
         else:
             both_branches = True
     if both_branches:
-        yield from self.body.infer(context=context)
-        yield from self.orelse.infer(context=context)
+        yield from self.body.infer(context=lhs_context)
+        yield from self.orelse.infer(context=rhs_context)
 
 
 nodes.IfExp._infer = infer_ifexp