[stubgenc] Generate Inline generics from __type_params__

mypy/stubdoc.py

@@ -108,6 +108,7 @@ def format_sig(
         is_async: bool = False,
         any_val: str | None = None,
         docstring: str | None = None,
+        generic: str = "",
     ) -> str:
         args: list[str] = []
         for arg in self.args:
@@ -141,8 +142,13 @@ def format_sig(
             retfield = " -> " + ret_type
 
         prefix = "async " if is_async else ""
-        sig = "{indent}{prefix}def {name}({args}){ret}:".format(
-            indent=indent, prefix=prefix, name=self.name, args=", ".join(args), ret=retfield
+        sig = "{indent}{prefix}def {name}{generic}({args}){ret}:".format(
+            indent=indent,
+            prefix=prefix,
+            name=self.name,
+            args=", ".join(args),
+            ret=retfield,
+            generic=generic,
         )
         if docstring:
             suffix = f"\n{indent}    {mypy.util.quote_docstring(docstring)}"

mypy/stubgenc.py

@@ -33,6 +33,7 @@
     ClassInfo,
     FunctionContext,
     SignatureGenerator,
+    generate_inline_generic,
     infer_method_arg_types,
     infer_method_ret_type,
 )
@@ -646,7 +647,17 @@ def generate_function_stub(
 
         if docstring:
             docstring = self._indent_docstring(docstring)
-        output.extend(self.format_func_def(inferred, decorators=decorators, docstring=docstring))
+
+        if hasattr(obj, "__type_params__"):
+            generic = generate_inline_generic(obj.__type_params__)
+        else:
+            generic = ""
+
+        output.extend(
+            self.format_func_def(
+                inferred, decorators=decorators, docstring=docstring, generic=generic
+            )
+        )
         self._fix_iter(ctx, inferred, output)
 
     def _indent_docstring(self, docstring: str) -> str:
@@ -847,10 +858,16 @@ def generate_class_stub(self, class_name: str, cls: type, output: list[str]) ->
             else:
                 attrs.append((attr, value))
 
+        inline_generic = ""
+
         for attr, value in attrs:
             if attr == "__hash__" and value is None:
                 # special case for __hash__
                 continue
+            elif attr == "__type_params__":
+                inline_generic = generate_inline_generic(value)
+                continue
+
             prop_type_name = self.strip_or_import(self.get_type_annotation(value))
             classvar = self.add_name("typing.ClassVar")
             static_properties.append(f"{self._indent}{attr}: {classvar}[{prop_type_name}] = ...")
@@ -882,7 +899,7 @@ def generate_class_stub(self, class_name: str, cls: type, output: list[str]) ->
             for line in ro_properties:
                 output.append(line)
         else:
-            output.append(f"{self._indent}class {class_name}{bases_str}: ...")
+            output.append(f"{self._indent}class {class_name}{inline_generic}{bases_str}: ...")
 
     def generate_variable_stub(self, name: str, obj: object, output: list[str]) -> None:
         """Generate stub for a single variable using runtime introspection.

mypy/stubutil.py

@@ -8,8 +8,8 @@
 from abc import abstractmethod
 from collections import defaultdict
 from contextlib import contextmanager
-from typing import Final, Iterable, Iterator, Mapping
-from typing_extensions import overload
+from typing import Final, Iterable, Iterator, Mapping, TypeVar, cast
+from typing_extensions import ParamSpec, TypeVarTuple, overload
 
 from mypy_extensions import mypyc_attr
 
@@ -766,6 +766,7 @@ def format_func_def(
         is_coroutine: bool = False,
         decorators: list[str] | None = None,
         docstring: str | None = None,
+        generic: str = "",
     ) -> list[str]:
         lines: list[str] = []
         if decorators is None:
@@ -781,6 +782,7 @@ def format_func_def(
                     indent=self._indent,
                     is_async=is_coroutine,
                     docstring=docstring if self._include_docstrings else None,
+                    generic=generic,
                 )
             )
         return lines
@@ -842,3 +844,37 @@ def should_reexport(self, name: str, full_module: str, name_is_alias: bool) -> b
         if self._all_:
             return name in self._all_
         return True
+
+
+def generate_inline_generic(type_params: tuple[TypeVar | ParamSpec | TypeVarTuple, ...]) -> str:
+    """Generate stub for inline generic from __type_params__"""
+
+    if len(type_params) == 0:
+        return ""
+
+    generic_arg_list: list[str] = []
+
+    for type_param in type_params:
+        # Not done with isinstance checks so compiled code doesn't necessarily need to use
+        # typing.TypeVar, just something with similar duck typing.
+        if hasattr(type_param, "__constraints__"):
+            # Is TypeVar
+            typevar = cast(TypeVar, type_param)
+            if typevar.__bound__:
+                generic_arg_list.append(f"{typevar.__name__}: {typevar.__bound__.__name__}")
+            elif typevar.__constraints__ != ():
+                generic_arg_list.append(
+                    f"{typevar.__name__}: ({', '.join([constraint.__name__ for constraint in typevar.__constraints__])})"
+                )
+            else:
+                generic_arg_list.append(f"{typevar.__name__}")
+        elif hasattr(type_param, "__bound__"):
+            # Is ParamSpec
+            param_spec = cast(ParamSpec, type_param)
+            generic_arg_list.append(f"**{param_spec.__name__}")
+        else:
+            # Is TypeVarTuple
+            generic_arg_list.append(f"*{type_param.__name__}")
+
+    flat_internals = ", ".join(generic_arg_list)
+    return f"[{flat_internals}]"

mypy/test/teststubgen.py

@@ -8,7 +8,8 @@
 import tempfile
 import unittest
 from types import ModuleType
-from typing import Any
+from typing import Any, Tuple, TypeVar, cast
+from typing_extensions import ParamSpec, TypeVarTuple
 
 import pytest
 
@@ -39,6 +40,7 @@
 from mypy.stubutil import (
     ClassInfo,
     common_dir_prefix,
+    generate_inline_generic,
     infer_method_ret_type,
     remove_misplaced_type_comments,
     walk_packages,
@@ -612,6 +614,29 @@ def test_common_dir_prefix_win(self) -> None:
         assert common_dir_prefix([r"foo\bar/x.pyi"]) == r"foo\bar"
         assert common_dir_prefix([r"foo/bar/x.pyi"]) == r"foo\bar"
 
+    def test_generate_inline_generic(self) -> None:
+        assert generate_inline_generic(()) == ""
+        T = TypeVar("T")
+        assert generate_inline_generic((T,)) == "[T]"
+        TBound = TypeVar("TBound", bound=int)
+        assert generate_inline_generic((TBound,)) == "[TBound: int]"
+        TBoundTuple = TypeVar("TBoundTuple", int, str)
+        assert generate_inline_generic((TBoundTuple,)) == "[TBoundTuple: (int, str)]"
+        P = ParamSpec("P")
+        p_tuple = cast(Tuple[ParamSpec], (P,))
+        assert generate_inline_generic(p_tuple) == "[**P]"
+        U = TypeVarTuple("U")
+        u_tuple = cast(Tuple[TypeVarTuple], (U,))
+        assert generate_inline_generic(u_tuple) == "[*U]"
+        all_tuple = cast(
+            Tuple[TypeVar, TypeVar, TypeVar, ParamSpec, TypeVarTuple],
+            (T, TBound, TBoundTuple, P, U),
+        )
+        assert (
+            generate_inline_generic(all_tuple)
+            == "[T, TBound: int, TBoundTuple: (int, str), **P, *U]"
+        )
+
 
 class StubgenHelpersSuite(unittest.TestCase):
     def test_is_blacklisted_path(self) -> None:
@@ -906,6 +931,50 @@ class TestClass(argparse.Action):
         assert_equal(output, ["class C(argparse.Action): ..."])
         assert_equal(gen.get_imports().splitlines(), ["import argparse"])
 
+    @unittest.skipIf(sys.version_info < (3, 12), "Inline Generics not supported before Python3.12")
+    def test_inline_generic_class(self) -> None:
+        T = TypeVar("T")
+
+        class TestClass:
+            __type_params__ = (T,)
+
+        output: list[str] = []
+        mod = ModuleType("module", "")
+        gen = InspectionStubGenerator(mod.__name__, known_modules=[mod.__name__], module=mod)
+        gen.generate_class_stub("C", TestClass, output)
+        assert_equal(output, ["class C[T]: ..."])
+
+    @unittest.skipIf(sys.version_info < (3, 12), "Inline Generics not supported before Python3.12")
+    def test_inline_generic_function(self) -> None:
+
+        if sys.version_info < (
+            3,
+            12,
+        ):  # Done to prevent mypy [attr-defined] error on __type_params__ in older versions of python
+            return
+
+        T = TypeVar("T", bound=int)
+
+        class TestClass:
+            def test(self, arg0: T) -> T:
+                """
+                test(self, arg0: T) -> T
+                """
+                return arg0
+
+            test.__type_params__ = (T,)
+
+        output: list[str] = []
+        mod = ModuleType(TestClass.__module__, "")
+        gen = InspectionStubGenerator(mod.__name__, known_modules=[mod.__name__], module=mod)
+        gen.generate_function_stub(
+            "test",
+            TestClass.test,
+            output=output,
+            class_info=ClassInfo(self_var="self", cls=TestClass, name="TestClass"),
+        )
+        assert_equal(output, ["def test[T: int](self, arg0: T) -> T: ..."])
+
     def test_generate_c_type_inheritance_builtin_type(self) -> None:
         class TestClass(type):
             pass