Add support for type parameter defaults + string repr improvements

ChangeLog

@@ -60,6 +60,11 @@ Release date: TBA
 
   refs #2789
 
+* Add support for type parameter defaults added in Python 3.13.
+
+* Improve ``as_string()`` representation for ``TypeVar``, ``ParamSpec`` and ``TypeVarTuple`` nodes, as well as
+  type parameter in ``ClassDef``, ``FuncDef`` and ``TypeAlias`` nodes (PEP 695).
+
 
 What's New in astroid 3.3.11?
 =============================

astroid/nodes/as_string.py

@@ -176,18 +176,27 @@ def visit_call(self, node: nodes.Call) -> str:
         args.extend(keywords)
         return f"{expr_str}({', '.join(args)})"
 
+    def _handle_type_params(
+        self, type_params: list[nodes.TypeVar | nodes.ParamSpec | nodes.TypeVarTuple]
+    ) -> str:
+        return (
+            f"[{', '.join(tp.accept(self) for tp in type_params)}]"
+            if type_params
+            else ""
+        )
+
     def visit_classdef(self, node: nodes.ClassDef) -> str:
         """return an astroid.ClassDef node as string"""
         decorate = node.decorators.accept(self) if node.decorators else ""
+        type_params = self._handle_type_params(node.type_params)
         args = [n.accept(self) for n in node.bases]
         if node._metaclass and not node.has_metaclass_hack():
             args.append("metaclass=" + node._metaclass.accept(self))
         args += [n.accept(self) for n in node.keywords]
         args_str = f"({', '.join(args)})" if args else ""
         docs = self._docs_dedent(node.doc_node)
-        # TODO: handle type_params
-        return "\n\n{}class {}{}:{}\n{}\n".format(
-            decorate, node.name, args_str, docs, self._stmt_list(node.body)
+        return "\n\n{}class {}{}{}:{}\n{}\n".format(
+            decorate, node.name, type_params, args_str, docs, self._stmt_list(node.body)
         )
 
     def visit_compare(self, node: nodes.Compare) -> str:
@@ -336,17 +345,18 @@ def visit_formattedvalue(self, node: nodes.FormattedValue) -> str:
     def handle_functiondef(self, node: nodes.FunctionDef, keyword: str) -> str:
         """return a (possibly async) function definition node as string"""
         decorate = node.decorators.accept(self) if node.decorators else ""
+        type_params = self._handle_type_params(node.type_params)
         docs = self._docs_dedent(node.doc_node)
         trailer = ":"
         if node.returns:
             return_annotation = " -> " + node.returns.as_string()
             trailer = return_annotation + ":"
-        # TODO: handle type_params
-        def_format = "\n%s%s %s(%s)%s%s\n%s"
+        def_format = "\n%s%s %s%s(%s)%s%s\n%s"
         return def_format % (
             decorate,
             keyword,
             node.name,
+            type_params,
             node.args.accept(self),
             trailer,
             docs,
@@ -455,7 +465,10 @@ def visit_nonlocal(self, node: nodes.Nonlocal) -> str:
 
     def visit_paramspec(self, node: nodes.ParamSpec) -> str:
         """return an astroid.ParamSpec node as string"""
-        return node.name.accept(self)
+        default_value_str = (
+            f" = {node.default_value.accept(self)}" if node.default_value else ""
+        )
+        return f"**{node.name.accept(self)}{default_value_str}"
 
     def visit_pass(self, node: nodes.Pass) -> str:
         """return an astroid.Pass node as string"""
@@ -545,15 +558,23 @@ def visit_tuple(self, node: nodes.Tuple) -> str:
 
     def visit_typealias(self, node: nodes.TypeAlias) -> str:
         """return an astroid.TypeAlias node as string"""
-        return node.name.accept(self) if node.name else "_"
+        type_params = self._handle_type_params(node.type_params)
+        return f"type {node.name.accept(self)}{type_params} = {node.value.accept(self)}"
 
     def visit_typevar(self, node: nodes.TypeVar) -> str:
         """return an astroid.TypeVar node as string"""
-        return node.name.accept(self) if node.name else "_"
+        bound_str = f": {node.bound.accept(self)}" if node.bound else ""
+        default_value_str = (
+            f" = {node.default_value.accept(self)}" if node.default_value else ""
+        )
+        return f"{node.name.accept(self)}{bound_str}{default_value_str}"
 
     def visit_typevartuple(self, node: nodes.TypeVarTuple) -> str:
         """return an astroid.TypeVarTuple node as string"""
-        return "*" + node.name.accept(self) if node.name else ""
+        default_value_str = (
+            f" = {node.default_value.accept(self)}" if node.default_value else ""
+        )
+        return f"*{node.name.accept(self)}{default_value_str}"
 
     def visit_unaryop(self, node: nodes.UnaryOp) -> str:
         """return an astroid.UnaryOp node as string"""

astroid/nodes/node_classes.py

@@ -3383,9 +3383,9 @@ class ParamSpec(_base_nodes.AssignTypeNode):
     <ParamSpec l.1 at 0x7f23b2e4e198>
     """
 
-    _astroid_fields = ("name",)
-
+    _astroid_fields = ("name", "default_value")
     name: AssignName
+    default_value: NodeNG | None
 
     def __init__(
         self,
@@ -3404,8 +3404,9 @@ def __init__(
             parent=parent,
         )
 
-    def postinit(self, *, name: AssignName) -> None:
+    def postinit(self, *, name: AssignName, default_value: NodeNG | None) -> None:
         self.name = name
+        self.default_value = default_value
 
     def _infer(
         self, context: InferenceContext | None = None, **kwargs: Any
@@ -4141,10 +4142,10 @@ class TypeVar(_base_nodes.AssignTypeNode):
     <TypeVar l.1 at 0x7f23b2e4e198>
     """
 
-    _astroid_fields = ("name", "bound")
-
+    _astroid_fields = ("name", "bound", "default_value")
     name: AssignName
     bound: NodeNG | None
+    default_value: NodeNG | None
 
     def __init__(
         self,
@@ -4163,9 +4164,16 @@ def __init__(
             parent=parent,
         )
 
-    def postinit(self, *, name: AssignName, bound: NodeNG | None) -> None:
+    def postinit(
+        self,
+        *,
+        name: AssignName,
+        bound: NodeNG | None,
+        default_value: NodeNG | None = None,
+    ) -> None:
         self.name = name
         self.bound = bound
+        self.default_value = default_value
 
     def _infer(
         self, context: InferenceContext | None = None, **kwargs: Any
@@ -4187,9 +4195,9 @@ class TypeVarTuple(_base_nodes.AssignTypeNode):
     <TypeVarTuple l.1 at 0x7f23b2e4e198>
     """
 
-    _astroid_fields = ("name",)
-
+    _astroid_fields = ("name", "default_value")
     name: AssignName
+    default_value: NodeNG | None
 
     def __init__(
         self,
@@ -4208,8 +4216,11 @@ def __init__(
             parent=parent,
         )
 
-    def postinit(self, *, name: AssignName) -> None:
+    def postinit(
+        self, *, name: AssignName, default_value: NodeNG | None = None
+    ) -> None:
         self.name = name
+        self.default_value = default_value
 
     def _infer(
         self, context: InferenceContext | None = None, **kwargs: Any

astroid/rebuilder.py

@@ -18,7 +18,7 @@
 
 from astroid import nodes
 from astroid._ast import ParserModule, get_parser_module, parse_function_type_comment
-from astroid.const import PY312_PLUS, Context
+from astroid.const import PY312_PLUS, PY313_PLUS, Context
 from astroid.nodes.utils import Position
 from astroid.typing import InferenceResult
 
@@ -1483,7 +1483,12 @@ def visit_paramspec(
         )
         # Add AssignName node for 'node.name'
         # https://bugs.python.org/issue43994
-        newnode.postinit(name=self.visit_assignname(node, newnode, node.name))
+        newnode.postinit(
+            name=self.visit_assignname(node, newnode, node.name),
+            default_value=(
+                self.visit(node.default_value, newnode) if PY313_PLUS else None
+            ),
+        )
         return newnode
 
     def visit_pass(self, node: ast.Pass, parent: nodes.NodeNG) -> nodes.Pass:
@@ -1679,6 +1684,9 @@ def visit_typevar(self, node: ast.TypeVar, parent: nodes.NodeNG) -> nodes.TypeVa
         newnode.postinit(
             name=self.visit_assignname(node, newnode, node.name),
             bound=self.visit(node.bound, newnode),
+            default_value=(
+                self.visit(node.default_value, newnode) if PY313_PLUS else None
+            ),
         )
         return newnode
 
@@ -1695,7 +1703,12 @@ def visit_typevartuple(
         )
         # Add AssignName node for 'node.name'
         # https://bugs.python.org/issue43994
-        newnode.postinit(name=self.visit_assignname(node, newnode, node.name))
+        newnode.postinit(
+            name=self.visit_assignname(node, newnode, node.name),
+            default_value=(
+                self.visit(node.default_value, newnode) if PY313_PLUS else None
+            ),
+        )
         return newnode
 
     def visit_unaryop(self, node: ast.UnaryOp, parent: nodes.NodeNG) -> nodes.UnaryOp:

tests/test_nodes.py

@@ -32,6 +32,7 @@
     IS_PYPY,
     PY311_PLUS,
     PY312_PLUS,
+    PY313_PLUS,
     PY314_PLUS,
     Context,
 )
@@ -332,27 +333,76 @@ def test_recursion_error_trapped() -> None:
 class AsStringTypeParamNodes(unittest.TestCase):
     @staticmethod
     def test_as_string_type_alias() -> None:
-        ast = abuilder.string_build("type Point = tuple[float, float]")
-        type_alias = ast.body[0]
-        assert type_alias.as_string().strip() == "Point"
+        ast1 = abuilder.string_build("type Point = tuple[float, float]")
+        type_alias1 = ast1.body[0]
+        assert type_alias1.as_string().strip() == "type Point = tuple[float, float]"
+        ast2 = abuilder.string_build(
+            "type Point[T, **P] = tuple[float, T, Callable[P, None]]"
+        )
+        type_alias2 = ast2.body[0]
+        assert (
+            type_alias2.as_string().strip()
+            == "type Point[T, **P] = tuple[float, T, Callable[P, None]]"
+        )
 
     @staticmethod
     def test_as_string_type_var() -> None:
-        ast = abuilder.string_build("type Point[T] = tuple[float, float]")
+        ast = abuilder.string_build("type Point[T: int | str] = tuple[float, float]")
+        type_var = ast.body[0].type_params[0]
+        assert type_var.as_string().strip() == "T: int | str"
+
+    @staticmethod
+    @pytest.mark.skipif(
+        not PY313_PLUS, reason="Type parameter defaults were added in 313"
+    )
+    def test_as_string_type_var_default() -> None:
+        ast = abuilder.string_build(
+            "type Point[T: int | str = int] = tuple[float, float]"
+        )
         type_var = ast.body[0].type_params[0]
-        assert type_var.as_string().strip() == "T"
+        assert type_var.as_string().strip() == "T: int | str = int"
 
     @staticmethod
     def test_as_string_type_var_tuple() -> None:
         ast = abuilder.string_build("type Alias[*Ts] = tuple[*Ts]")
         type_var_tuple = ast.body[0].type_params[0]
         assert type_var_tuple.as_string().strip() == "*Ts"
 
+    @staticmethod
+    @pytest.mark.skipif(
+        not PY313_PLUS, reason="Type parameter defaults were added in 313"
+    )
+    def test_as_string_type_var_tuple_defaults() -> None:
+        ast = abuilder.string_build("type Alias[*Ts = tuple[int, str]] = tuple[*Ts]")
+        type_var_tuple = ast.body[0].type_params[0]
+        assert type_var_tuple.as_string().strip() == "*Ts = tuple[int, str]"
+
     @staticmethod
     def test_as_string_param_spec() -> None:
         ast = abuilder.string_build("type Alias[**P] = Callable[P, int]")
         param_spec = ast.body[0].type_params[0]
-        assert param_spec.as_string().strip() == "P"
+        assert param_spec.as_string().strip() == "**P"
+
+    @staticmethod
+    @pytest.mark.skipif(
+        not PY313_PLUS, reason="Type parameter defaults were added in 313"
+    )
+    def test_as_string_param_spec_defaults() -> None:
+        ast = abuilder.string_build("type Alias[**P = [str, int]] = Callable[P, int]")
+        param_spec = ast.body[0].type_params[0]
+        assert param_spec.as_string().strip() == "**P = [str, int]"
+
+    @staticmethod
+    def test_as_string_class_type_params() -> None:
+        code = abuilder.string_build("class A[T, **P]: ...")
+        cls_node = code.body[0]
+        assert cls_node.as_string().strip() == "class A[T, **P]:\n    ..."
+
+    @staticmethod
+    def test_as_string_function_type_params() -> None:
+        code = abuilder.string_build("def func[T, **P](): ...")
+        func_node = code.body[0]
+        assert func_node.as_string().strip() == "def func[T, **P]():\n    ..."
 
 
 class _NodeTest(unittest.TestCase):