Make ClassDef.metaclass an Expression

mypy/fastparse.py

@@ -465,20 +465,14 @@ def fail_arg(msg: str, arg: ast3.arg) -> None:
     @with_line
     def visit_ClassDef(self, n: ast3.ClassDef) -> ClassDef:
         self.class_nesting += 1
-        metaclass_arg = find(lambda x: x.arg == 'metaclass', n.keywords)
-        metaclass = None
-        if metaclass_arg:
-            metaclass = stringify_name(metaclass_arg.value)
-            if metaclass is None:
-                metaclass = '<error>'  # To be reported later
         keywords = [(kw.arg, self.visit(kw.value))
                     for kw in n.keywords]
 
         cdef = ClassDef(n.name,
                         self.as_block(n.body, n.lineno),
                         None,
                         self.translate_expr_list(n.bases),
-                        metaclass=metaclass,
+                        metaclass=dict(keywords).get('metaclass'),
                         keywords=keywords)
         cdef.decorators = self.translate_expr_list(n.decorator_list)
         self.class_nesting -= 1

mypy/nodes.py

@@ -730,7 +730,7 @@ class ClassDef(Statement):
     # Base class expressions (not semantically analyzed -- can be arbitrary expressions)
     base_type_exprs = None  # type: List[Expression]
     info = None  # type: TypeInfo  # Related TypeInfo
-    metaclass = ''  # type: Optional[str]
+    metaclass = None  # type: Optional[Expression]
     decorators = None  # type: List[Expression]
     keywords = None  # type: OrderedDict[str, Expression]
     analyzed = None  # type: Optional[Expression]
@@ -741,7 +741,7 @@ def __init__(self,
                  defs: 'Block',
                  type_vars: Optional[List['mypy.types.TypeVarDef']] = None,
                  base_type_exprs: Optional[List[Expression]] = None,
-                 metaclass: Optional[str] = None,
+                 metaclass: Optional[Expression] = None,
                  keywords: Optional[List[Tuple[str, Expression]]] = None) -> None:
         self.name = name
         self.defs = defs
@@ -758,12 +758,12 @@ def is_generic(self) -> bool:
         return self.info.is_generic()
 
     def serialize(self) -> JsonDict:
-        # Not serialized: defs, base_type_exprs, decorators, analyzed (for named tuples etc.)
+        # Not serialized: defs, base_type_exprs, metaclass, decorators,
+        # analyzed (for named tuples etc.)
         return {'.class': 'ClassDef',
                 'name': self.name,
                 'fullname': self.fullname,
                 'type_vars': [v.serialize() for v in self.type_vars],
-                'metaclass': self.metaclass,
                 }
 
     @classmethod
@@ -772,7 +772,6 @@ def deserialize(self, data: JsonDict) -> 'ClassDef':
         res = ClassDef(data['name'],
                        Block([]),
                        [mypy.types.TypeVarDef.deserialize(v) for v in data['type_vars']],
-                       metaclass=data['metaclass'],
                        )
         res.fullname = data['fullname']
         return res

mypy/semanal.py

@@ -1089,26 +1089,18 @@ def analyze_base_classes(self, defn: ClassDef) -> None:
         if defn.info.is_enum and defn.type_vars:
             self.fail("Enum class cannot be generic", defn)
 
-    def check_with_metaclass(self, defn: ClassDef) -> Tuple[List[Expression], Optional[str]]:
+    def check_with_metaclass(self, defn: ClassDef) -> Tuple[List[Expression],
+                                                            Optional[Expression]]:
         # Special-case six.with_metaclass(M, B1, B2, ...).
-        base_type_exprs, metaclass = defn.base_type_exprs, defn.metaclass
-        if metaclass is None and len(base_type_exprs) == 1:
-            base_expr = base_type_exprs[0]
+        if defn.metaclass is None and len(defn.base_type_exprs) == 1:
+            base_expr = defn.base_type_exprs[0]
             if isinstance(base_expr, CallExpr) and isinstance(base_expr.callee, RefExpr):
                 base_expr.callee.accept(self)
                 if (base_expr.callee.fullname == 'six.with_metaclass'
                         and len(base_expr.args) >= 1
                         and all(kind == ARG_POS for kind in base_expr.arg_kinds)):
-                    metaclass_expr = base_expr.args[0]
-                    if isinstance(metaclass_expr, NameExpr):
-                        metaclass = metaclass_expr.name
-                    elif isinstance(metaclass_expr, MemberExpr):
-                        metaclass = get_member_expr_fullname(metaclass_expr)
-                    else:
-                        self.fail("Dynamic metaclass not supported for '%s'" % defn.name,
-                                  metaclass_expr)
-                    return (base_expr.args[1:], metaclass)
-        return (base_type_exprs, metaclass)
+                    return (base_expr.args[1:], base_expr.args[0])
+        return (defn.base_type_exprs, defn.metaclass)
 
     def expr_to_analyzed_type(self, expr: Expression) -> Type:
         if isinstance(expr, CallExpr):
@@ -1157,7 +1149,6 @@ def is_base_class(self, t: TypeInfo, s: TypeInfo) -> bool:
         return False
 
     def analyze_metaclass(self, defn: ClassDef) -> None:
-        error_context = defn  # type: Context
         if defn.metaclass is None and self.options.python_version[0] == 2:
             # Look for "__metaclass__ = <metaclass>" in Python 2.
             for body_node in defn.defs.body:
@@ -1167,26 +1158,16 @@ def analyze_metaclass(self, defn: ClassDef) -> None:
                 elif isinstance(body_node, AssignmentStmt) and len(body_node.lvalues) == 1:
                     lvalue = body_node.lvalues[0]
                     if isinstance(lvalue, NameExpr) and lvalue.name == "__metaclass__":
-                        error_context = body_node.rvalue
-                        if isinstance(body_node.rvalue, NameExpr):
-                            name = body_node.rvalue.name
-                        elif isinstance(body_node.rvalue, MemberExpr):
-                            name = get_member_expr_fullname(body_node.rvalue)
-                        else:
-                            name = None
-                        if name:
-                            defn.metaclass = name
-                        else:
-                            self.fail(
-                                "Dynamic metaclass not supported for '%s'" % defn.name,
-                                body_node
-                            )
-                            return
+                        defn.metaclass = body_node.rvalue
         if defn.metaclass:
-            if defn.metaclass == '<error>':
-                self.fail("Dynamic metaclass not supported for '%s'" % defn.name, error_context)
+            if isinstance(defn.metaclass, NameExpr):
+                metaclass_name = defn.metaclass.name
+            elif isinstance(defn.metaclass, MemberExpr):
+                metaclass_name = get_member_expr_fullname(defn.metaclass)
+            else:
+                self.fail("Dynamic metaclass not supported for '%s'" % defn.name, defn.metaclass)
                 return
-            sym = self.lookup_qualified(defn.metaclass, error_context)
+            sym = self.lookup_qualified(metaclass_name, defn.metaclass)
             if sym is None:
                 # Probably a name error - it is already handled elsewhere
                 return
@@ -1198,10 +1179,11 @@ def analyze_metaclass(self, defn: ClassDef) -> None:
                 #       attributes, similar to an 'Any' base class.
                 return
             if not isinstance(sym.node, TypeInfo) or sym.node.tuple_type is not None:
-                self.fail("Invalid metaclass '%s'" % defn.metaclass, defn)
+                self.fail("Invalid metaclass '%s'" % metaclass_name, defn.metaclass)
                 return
             if not sym.node.is_metaclass():
-                self.fail("Metaclasses not inheriting from 'type' are not supported", defn)
+                self.fail("Metaclasses not inheriting from 'type' are not supported",
+                          defn.metaclass)
                 return
             inst = fill_typevars(sym.node)
             assert isinstance(inst, Instance)

mypy/treetransform.py

@@ -177,7 +177,7 @@ def visit_class_def(self, node: ClassDef) -> ClassDef:
                        self.block(node.defs),
                        node.type_vars,
                        self.expressions(node.base_type_exprs),
-                       node.metaclass)
+                       self.optional_expr(node.metaclass))
         new.fullname = node.fullname
         new.info = node.info
         new.decorators = [self.expr(decorator)

test-data/unit/parse.test

@@ -2480,7 +2480,7 @@ class Foo(metaclass=Bar): pass
 MypyFile:1(
   ClassDef:1(
     Foo
-    Metaclass(Bar)
+    Metaclass(NameExpr(Bar))
     PassStmt:1()))
 
 [case testQualifiedMetaclass]
@@ -2489,7 +2489,9 @@ class Foo(metaclass=foo.Bar): pass
 MypyFile:1(
   ClassDef:1(
     Foo
-    Metaclass(foo.Bar)
+    Metaclass(MemberExpr:1(
+      NameExpr(foo)
+      Bar))
     PassStmt:1()))
 
 [case testBaseAndMetaclass]
@@ -2498,7 +2500,7 @@ class Foo(foo.bar[x], metaclass=Bar): pass
 MypyFile:1(
   ClassDef:1(
     Foo
-    Metaclass(Bar)
+    Metaclass(NameExpr(Bar))
     BaseTypeExpr(
       IndexExpr:1(
         MemberExpr:1(
@@ -2521,7 +2523,7 @@ class Foo(_root=None, metaclass=Bar): pass
 MypyFile:1(
   ClassDef:1(
     Foo
-    Metaclass(Bar)
+    Metaclass(NameExpr(Bar))
     PassStmt:1()))
 
 [case testClassKeywordArgsAfterMeta]
@@ -2530,7 +2532,7 @@ class Foo(metaclass=Bar, _root=None): pass
 MypyFile:1(
   ClassDef:1(
     Foo
-    Metaclass(Bar)
+    Metaclass(NameExpr(Bar))
     PassStmt:1()))
 
 [case testNamesThatAreNoLongerKeywords]

test-data/unit/semanal-abstractclasses.test

@@ -13,7 +13,7 @@ MypyFile:1(
   Import:2(typing)
   ClassDef:4(
     A
-    Metaclass(ABCMeta)
+    Metaclass(NameExpr(ABCMeta [abc.ABCMeta]))
     Decorator:5(
       Var(g)
       FuncDef:6(
@@ -49,11 +49,11 @@ MypyFile:1(
   Import:2(typing)
   ClassDef:4(
     A
-    Metaclass(ABCMeta)
+    Metaclass(NameExpr(ABCMeta [abc.ABCMeta]))
     PassStmt:4())
   ClassDef:5(
     B
-    Metaclass(ABCMeta)
+    Metaclass(NameExpr(ABCMeta [abc.ABCMeta]))
     PassStmt:5())
   ClassDef:6(
     C
@@ -106,7 +106,7 @@ MypyFile:1(
   Import:3(typing)
   ClassDef:5(
     A
-    Metaclass(ABCMeta)
+    Metaclass(NameExpr(ABCMeta [abc.ABCMeta]))
     Decorator:6(
       Var(g)
       FuncDef:7(

test-data/unit/semanal-classes.test

@@ -411,7 +411,9 @@ MypyFile:1(
   Import:1(abc)
   ClassDef:2(
     A
-    Metaclass(abc.ABCMeta)
+    Metaclass(MemberExpr:2(
+      NameExpr(abc)
+      ABCMeta [abc.ABCMeta]))
     PassStmt:2()))
 
 [case testStaticMethod]