add support for dataclasses (#5010)

This adds basic support for dataclasses in Python 3.7.
In particular dataclass decorator, fields, factories, inheritance,
and InitVars are supported.

Author: Bogdanp

mypy/plugin.py

@@ -4,7 +4,6 @@
 from functools import partial
 from typing import Callable, List, Tuple, Optional, NamedTuple, TypeVar, Dict
 
-import mypy.plugins.attrs
 from mypy.nodes import (
     Expression, StrExpr, IntExpr, UnaryExpr, Context, DictExpr, ClassDef,
     TypeInfo, SymbolTableNode, MypyFile
@@ -302,13 +301,18 @@ def get_method_hook(self, fullname: str
 
     def get_class_decorator_hook(self, fullname: str
                                  ) -> Optional[Callable[[ClassDefContext], None]]:
-        if fullname in mypy.plugins.attrs.attr_class_makers:
-            return mypy.plugins.attrs.attr_class_maker_callback
-        elif fullname in mypy.plugins.attrs.attr_dataclass_makers:
+        from mypy.plugins import attrs
+        from mypy.plugins import dataclasses
+
+        if fullname in attrs.attr_class_makers:
+            return attrs.attr_class_maker_callback
+        elif fullname in attrs.attr_dataclass_makers:
             return partial(
-                mypy.plugins.attrs.attr_class_maker_callback,
+                attrs.attr_class_maker_callback,
                 auto_attribs_default=True
             )
+        elif fullname in dataclasses.dataclass_makers:
+            return dataclasses.dataclass_class_maker_callback
         return None
 
 

mypy/plugins/attrs.py

@@ -11,6 +11,9 @@
     is_class_var, TempNode, Decorator, MemberExpr, Expression, FuncDef, Block,
     PassStmt, SymbolTableNode, MDEF, JsonDict, OverloadedFuncDef
 )
+from mypy.plugins.common import (
+    _get_argument, _get_bool_argument, _get_decorator_bool_argument
+)
 from mypy.types import (
     Type, AnyType, TypeOfAny, CallableType, NoneTyp, TypeVarDef, TypeVarType,
     Overloaded, Instance, UnionType, FunctionLike
@@ -468,67 +471,6 @@ def _add_init(ctx: 'mypy.plugin.ClassDefContext', attributes: List[Attribute],
                 func_type.arg_types[0] = ctx.api.class_type(ctx.cls.info)
 
 
-def _get_decorator_bool_argument(
-        ctx: 'mypy.plugin.ClassDefContext',
-        name: str,
-        default: bool) -> bool:
-    """Return the bool argument for the decorator.
-
-    This handles both @attr.s(...) and @attr.s
-    """
-    if isinstance(ctx.reason, CallExpr):
-        return _get_bool_argument(ctx, ctx.reason, name, default)
-    else:
-        return default
-
-
-def _get_bool_argument(ctx: 'mypy.plugin.ClassDefContext', expr: CallExpr,
-                       name: str, default: bool) -> bool:
-    """Return the boolean value for an argument to a call or the default if it's not found."""
-    attr_value = _get_argument(expr, name)
-    if attr_value:
-        ret = ctx.api.parse_bool(attr_value)
-        if ret is None:
-            ctx.api.fail('"{}" argument must be True or False.'.format(name), expr)
-            return default
-        return ret
-    return default
-
-
-def _get_argument(call: CallExpr, name: str) -> Optional[Expression]:
-    """Return the expression for the specific argument."""
-    # To do this we use the CallableType of the callee to find the FormalArgument,
-    # then walk the actual CallExpr looking for the appropriate argument.
-    #
-    # Note: I'm not hard-coding the index so that in the future we can support other
-    # attrib and class makers.
-    callee_type = None
-    if (isinstance(call.callee, RefExpr)
-            and isinstance(call.callee.node, (Var, FuncBase))
-            and call.callee.node.type):
-        callee_node_type = call.callee.node.type
-        if isinstance(callee_node_type, Overloaded):
-            # We take the last overload.
-            callee_type = callee_node_type.items()[-1]
-        elif isinstance(callee_node_type, CallableType):
-            callee_type = callee_node_type
-
-    if not callee_type:
-        return None
-
-    argument = callee_type.argument_by_name(name)
-    if not argument:
-        return None
-    assert argument.name
-
-    for i, (attr_name, attr_value) in enumerate(zip(call.arg_names, call.args)):
-        if argument.pos is not None and not attr_name and i == argument.pos:
-            return attr_value
-        if attr_name == argument.name:
-            return attr_value
-    return None
-
-
 class MethodAdder:
     """Helper to add methods to a TypeInfo.
 

mypy/plugins/common.py

@@ -0,0 +1,110 @@
+from typing import List, Optional
+
+from mypy.nodes import (
+    ARG_OPT, ARG_POS, MDEF, Argument, Block, CallExpr, Expression, FuncBase,
+    FuncDef, PassStmt, RefExpr, SymbolTableNode, Var
+)
+from mypy.plugin import ClassDefContext
+from mypy.semanal import set_callable_name
+from mypy.types import CallableType, Overloaded, Type, TypeVarDef
+from mypy.typevars import fill_typevars
+
+
+def _get_decorator_bool_argument(
+        ctx: ClassDefContext,
+        name: str,
+        default: bool,
+) -> bool:
+    """Return the bool argument for the decorator.
+
+    This handles both @decorator(...) and @decorator.
+    """
+    if isinstance(ctx.reason, CallExpr):
+        return _get_bool_argument(ctx, ctx.reason, name, default)
+    else:
+        return default
+
+
+def _get_bool_argument(ctx: ClassDefContext, expr: CallExpr,
+                       name: str, default: bool) -> bool:
+    """Return the boolean value for an argument to a call or the
+    default if it's not found.
+    """
+    attr_value = _get_argument(expr, name)
+    if attr_value:
+        ret = ctx.api.parse_bool(attr_value)
+        if ret is None:
+            ctx.api.fail('"{}" argument must be True or False.'.format(name), expr)
+            return default
+        return ret
+    return default
+
+
+def _get_argument(call: CallExpr, name: str) -> Optional[Expression]:
+    """Return the expression for the specific argument."""
+    # To do this we use the CallableType of the callee to find the FormalArgument,
+    # then walk the actual CallExpr looking for the appropriate argument.
+    #
+    # Note: I'm not hard-coding the index so that in the future we can support other
+    # attrib and class makers.
+    callee_type = None
+    if (isinstance(call.callee, RefExpr)
+            and isinstance(call.callee.node, (Var, FuncBase))
+            and call.callee.node.type):
+        callee_node_type = call.callee.node.type
+        if isinstance(callee_node_type, Overloaded):
+            # We take the last overload.
+            callee_type = callee_node_type.items()[-1]
+        elif isinstance(callee_node_type, CallableType):
+            callee_type = callee_node_type
+
+    if not callee_type:
+        return None
+
+    argument = callee_type.argument_by_name(name)
+    if not argument:
+        return None
+    assert argument.name
+
+    for i, (attr_name, attr_value) in enumerate(zip(call.arg_names, call.args)):
+        if argument.pos is not None and not attr_name and i == argument.pos:
+            return attr_value
+        if attr_name == argument.name:
+            return attr_value
+    return None
+
+
+def _add_method(
+        ctx: ClassDefContext,
+        name: str,
+        args: List[Argument],
+        return_type: Type,
+        self_type: Optional[Type] = None,
+        tvar_def: Optional[TypeVarDef] = None,
+) -> None:
+    """Adds a new method to a class.
+    """
+    info = ctx.cls.info
+    self_type = self_type or fill_typevars(info)
+    function_type = ctx.api.named_type('__builtins__.function')
+
+    args = [Argument(Var('self'), self_type, None, ARG_POS)] + args
+    arg_types, arg_names, arg_kinds = [], [], []
+    for arg in args:
+        assert arg.type_annotation, 'All arguments must be fully typed.'
+        arg_types.append(arg.type_annotation)
+        arg_names.append(arg.variable.name())
+        arg_kinds.append(arg.kind)
+
+    signature = CallableType(arg_types, arg_kinds, arg_names, return_type, function_type)
+    if tvar_def:
+        signature.variables = [tvar_def]
+
+    func = FuncDef(name, args, Block([PassStmt()]))
+    func.info = info
+    func.type = set_callable_name(signature, func)
+    func._fullname = info.fullname() + '.' + name
+    func.line = info.line
+
+    info.names[name] = SymbolTableNode(MDEF, func)
+    info.defn.defs.body.append(func)