Add typing to ``brain_dataclasses`` (#1292)

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>
Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>

1 files changed, 44 insertions, 28 deletions

diff --git a/astroid/brain/brain_dataclasses.py b/astroid/brain/brain_dataclasses.py
index a05c46f9..bfdbbe09 100644
--- a/astroid/brain/brain_dataclasses.py
+++ b/astroid/brain/brain_dataclasses.py
@@ -10,7 +10,8 @@ dataclasses. References:
 - https://lovasoa.github.io/marshmallow_dataclass/
 
 """
-from typing import FrozenSet, Generator, List, Optional, Tuple
+import sys
+from typing import FrozenSet, Generator, List, Optional, Tuple, Union
 
 from astroid import context, inference_tip
 from astroid.builder import parse
@@ -36,6 +37,15 @@ from astroid.nodes.node_classes import (
 from astroid.nodes.scoped_nodes import ClassDef, FunctionDef
 from astroid.util import Uninferable
 
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
+
+_FieldDefaultReturn = Union[
+    None, Tuple[Literal["default"], NodeNG], Tuple[Literal["default_factory"], Call]
+]
+
 DATACLASSES_DECORATORS = frozenset(("dataclass",))
 FIELD_NAME = "field"
 DATACLASS_MODULES = frozenset(
@@ -115,7 +125,7 @@ def _get_dataclass_attributes(node: ClassDef, init: bool = False) -> Generator:
         ):
             continue
 
-        if _is_class_var(assign_node.annotation):
+        if _is_class_var(assign_node.annotation):  # type: ignore[arg-type] # annotation is never None
             continue
 
         if init:
@@ -124,12 +134,13 @@ def _get_dataclass_attributes(node: ClassDef, init: bool = False) -> Generator:
                 isinstance(value, Call)
                 and _looks_like_dataclass_field_call(value, check_scope=False)
                 and any(
-                    keyword.arg == "init" and not keyword.value.bool_value()
+                    keyword.arg == "init"
+                    and not keyword.value.bool_value()  # type: ignore[union-attr] # value is never None
                     for keyword in value.keywords
                 )
             ):
                 continue
-        elif _is_init_var(assign_node.annotation):
+        elif _is_init_var(assign_node.annotation):  # type: ignore[arg-type] # annotation is never None
             continue
 
         yield assign_node
@@ -159,7 +170,8 @@ def _check_generate_dataclass_init(node: ClassDef) -> bool:
 
     # Check for keyword arguments of the form init=False
     return all(
-        keyword.arg != "init" or keyword.value.bool_value()
+        keyword.arg != "init"
+        and keyword.value.bool_value()  # type: ignore[union-attr] # value is never None
         for keyword in found.keywords
     )
 
@@ -174,7 +186,7 @@ def _generate_dataclass_init(assigns: List[AnnAssign]) -> str:
         name, annotation, value = assign.target.name, assign.annotation, assign.value
         target_names.append(name)
 
-        if _is_init_var(annotation):
+        if _is_init_var(annotation):  # type: ignore[arg-type] # annotation is never None
             init_var = True
             if isinstance(annotation, Subscript):
                 annotation = annotation.slice
@@ -196,16 +208,16 @@ def _generate_dataclass_init(assigns: List[AnnAssign]) -> str:
                 value, check_scope=False
             ):
                 result = _get_field_default(value)
-
-                default_type, default_node = result
-                if default_type == "default":
-                    param_str += f" = {default_node.as_string()}"
-                elif default_type == "default_factory":
-                    param_str += f" = {DEFAULT_FACTORY}"
-                    assignment_str = (
-                        f"self.{name} = {default_node.as_string()} "
-                        f"if {name} is {DEFAULT_FACTORY} else {name}"
-                    )
+                if result:
+                    default_type, default_node = result
+                    if default_type == "default":
+                        param_str += f" = {default_node.as_string()}"
+                    elif default_type == "default_factory":
+                        param_str += f" = {DEFAULT_FACTORY}"
+                        assignment_str = (
+                            f"self.{name} = {default_node.as_string()} "
+                            f"if {name} is {DEFAULT_FACTORY} else {name}"
+                        )
             else:
                 param_str += f" = {value.as_string()}"
 
@@ -219,7 +231,7 @@ def _generate_dataclass_init(assigns: List[AnnAssign]) -> str:
 
 
 def infer_dataclass_attribute(
-    node: Unknown, ctx: context.InferenceContext = None
+    node: Unknown, ctx: Optional[context.InferenceContext] = None
 ) -> Generator:
     """Inference tip for an Unknown node that was dynamically generated to
     represent a dataclass attribute.
@@ -247,16 +259,17 @@ def infer_dataclass_field_call(
     """Inference tip for dataclass field calls."""
     if not isinstance(node.parent, (AnnAssign, Assign)):
         raise UseInferenceDefault
-    field_call = node.parent.value
-    default_type, default = _get_field_default(field_call)
-    if not default_type:
+    result = _get_field_default(node)
+    if not result:
         yield Uninferable
-    elif default_type == "default":
-        yield from default.infer(context=ctx)
     else:
-        new_call = parse(default.as_string()).body[0].value
-        new_call.parent = field_call.parent
-        yield from new_call.infer(context=ctx)
+        default_type, default = result
+        if default_type == "default":
+            yield from default.infer(context=ctx)
+        else:
+            new_call = parse(default.as_string()).body[0].value
+            new_call.parent = node.parent
+            yield from new_call.infer(context=ctx)
 
 
 def _looks_like_dataclass_decorator(
@@ -294,6 +307,9 @@ def _looks_like_dataclass_attribute(node: Unknown) -> bool:
     statement.
     """
     parent = node.parent
+    if not parent:
+        return False
+
     scope = parent.scope()
     return (
         isinstance(parent, AnnAssign)
@@ -330,7 +346,7 @@ def _looks_like_dataclass_field_call(node: Call, check_scope: bool = True) -> bo
     return inferred.name == FIELD_NAME and inferred.root().name in DATACLASS_MODULES
 
 
-def _get_field_default(field_call: Call) -> Tuple[str, Optional[NodeNG]]:
+def _get_field_default(field_call: Call) -> _FieldDefaultReturn:
     """Return a the default value of a field call, and the corresponding keyword argument name.
 
     field(default=...) results in the ... node
@@ -358,7 +374,7 @@ def _get_field_default(field_call: Call) -> Tuple[str, Optional[NodeNG]]:
         new_call.postinit(func=default_factory)
         return "default_factory", new_call
 
-    return "", None
+    return None
 
 
 def _is_class_var(node: NodeNG) -> bool:
@@ -404,7 +420,7 @@ _INFERABLE_TYPING_TYPES = frozenset(
 
 
 def _infer_instance_from_annotation(
-    node: NodeNG, ctx: context.InferenceContext = None
+    node: NodeNG, ctx: Optional[context.InferenceContext] = None
 ) -> Generator:
     """Infer an instance corresponding to the type annotation represented by node.