feat: Correct stubs for TypeVars (#67)

Closes #63

### Summary of Changes
TypeVars create correct stubs.

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>

src/safeds_stubgen/api_analyzer/_api.py

@@ -16,7 +16,7 @@
         ResultDocstring,
     )
 
-    from ._types import AbstractType
+    from ._types import AbstractType, TypeVarType
 
 API_SCHEMA_VERSION = 1
 
@@ -237,6 +237,7 @@ class Function:
     is_static: bool
     is_class_method: bool
     is_property: bool
+    type_var_types: list[TypeVarType] = field(default_factory=list)
     results: list[Result] = field(default_factory=list)
     reexported_by: list[Module] = field(default_factory=list)
     parameters: list[Parameter] = field(default_factory=list)
@@ -311,11 +312,15 @@ class ParameterAssignment(PythonEnum):
 @dataclass(frozen=True)
 class TypeParameter:
     name: str
-    type: AbstractType
+    type: AbstractType | None
     variance: VarianceKind
 
     def to_dict(self) -> dict[str, Any]:
-        return {"name": self.name, "type": self.type.to_dict(), "variance_type": self.variance.name}
+        return {
+            "name": self.name,
+            "type": self.type.to_dict() if self.type is not None else None,
+            "variance_type": self.variance.name,
+        }
 
 
 class VarianceKind(PythonEnum):

src/safeds_stubgen/api_analyzer/_ast_visitor.py

@@ -50,6 +50,8 @@ def __init__(self, docstring_parser: AbstractDocstringParser, api: API, aliases:
         self.__declaration_stack: list[Module | Class | Function | Enum | list[Attribute | EnumInstance]] = []
         self.aliases = aliases
         self.mypy_file: mp_nodes.MypyFile | None = None
+        # We gather type var types used as a parameter type in a function
+        self.type_var_types: set[sds_types.TypeVarType] = set()
 
     def enter_moduledef(self, node: mp_nodes.MypyFile) -> None:
         self.mypy_file = node
@@ -153,13 +155,17 @@ def enter_classdef(self, node: mp_nodes.ClassDef) -> None:
 
             for generic_type in generic_types:
                 variance_type = mypy_variance_parser(generic_type.variance)
-                variance_values: sds_types.AbstractType
+                variance_values: sds_types.AbstractType | None = None
                 if variance_type == VarianceKind.INVARIANT:
-                    variance_values = sds_types.UnionType(
-                        [self.mypy_type_to_abstract_type(value) for value in generic_type.values],
-                    )
+                    values = [self.mypy_type_to_abstract_type(value) for value in generic_type.values]
+                    if values:
+                        variance_values = sds_types.UnionType(
+                            [self.mypy_type_to_abstract_type(value) for value in generic_type.values],
+                        )
                 else:
-                    variance_values = self.mypy_type_to_abstract_type(generic_type.upper_bound)
+                    upper_bound = generic_type.upper_bound
+                    if upper_bound.__str__() != "builtins.object":
+                        variance_values = self.mypy_type_to_abstract_type(upper_bound)
 
                 type_parameters.append(
                     TypeParameter(
@@ -229,11 +235,19 @@ def enter_funcdef(self, node: mp_nodes.FuncDef) -> None:
         # Get docstring
         docstring = self.docstring_parser.get_function_documentation(node)
 
-        # Function args
+        # Function args & TypeVar
         arguments: list[Parameter] = []
+        type_var_types: list[sds_types.TypeVarType] = []
+        # Reset the type_var_types list
+        self.type_var_types = set()
         if getattr(node, "arguments", None) is not None:
             arguments = self._parse_parameter_data(node, function_id)
 
+            if self.type_var_types:
+                type_var_types = list(self.type_var_types)
+                # Sort for the snapshot tests
+                type_var_types.sort(key=lambda x: x.name)
+
         # Create results
         results = self._parse_results(node, function_id)
 
@@ -252,6 +266,7 @@ def enter_funcdef(self, node: mp_nodes.FuncDef) -> None:
             results=results,
             reexported_by=reexported_by,
             parameters=arguments,
+            type_var_types=type_var_types,
         )
         self.__declaration_stack.append(function)
 
@@ -666,7 +681,7 @@ def _parse_parameter_data(self, node: mp_nodes.FuncDef, function_id: str) -> lis
         for argument in node.arguments:
             mypy_type = argument.variable.type
             type_annotation = argument.type_annotation
-            arg_type = None
+            arg_type: AbstractType | None = None
             default_value = None
             default_is_none = False
 
@@ -827,7 +842,14 @@ def mypy_type_to_abstract_type(
 
         # Special Cases
         elif isinstance(mypy_type, mp_types.TypeVarType):
-            return sds_types.TypeVarType(mypy_type.name)
+            upper_bound = mypy_type.upper_bound
+            type_ = None
+            if upper_bound.__str__() != "builtins.object":
+                type_ = self.mypy_type_to_abstract_type(upper_bound)
+
+            type_var = sds_types.TypeVarType(name=mypy_type.name, upper_bound=type_)
+            self.type_var_types.add(type_var)
+            return type_var
         elif isinstance(mypy_type, mp_types.CallableType):
             return sds_types.CallableType(
                 parameter_types=[self.mypy_type_to_abstract_type(arg_type) for arg_type in mypy_type.arg_types],

src/safeds_stubgen/api_analyzer/_types.py

@@ -391,16 +391,21 @@ def __hash__(self) -> int:
 @dataclass(frozen=True)
 class TypeVarType(AbstractType):
     name: str
+    upper_bound: AbstractType | None = None
 
     @classmethod
-    def from_dict(cls, d: dict[str, str]) -> TypeVarType:
-        return TypeVarType(d["name"])
+    def from_dict(cls, d: dict[str, Any]) -> TypeVarType:
+        return TypeVarType(d["name"], d["upper_bound"])
 
-    def to_dict(self) -> dict[str, str]:
-        return {"kind": self.__class__.__name__, "name": self.name}
+    def to_dict(self) -> dict[str, Any]:
+        return {
+            "kind": self.__class__.__name__,
+            "name": self.name,
+            "upper_bound": self.upper_bound.to_dict() if self.upper_bound is not None else None,
+        }
 
     def __hash__(self) -> int:
-        return hash(frozenset([self.name]))
+        return hash(frozenset([self.name, self.upper_bound]))
 
 
 # ############################## Utilities ############################## #

src/safeds_stubgen/stubs_generator/_generate_stubs.py

@@ -88,6 +88,7 @@ def __call__(self, module: Module) -> str:
         self.module_imports = set()
         self._current_todo_msgs: set[str] = set()
         self.module = module
+        self.class_generics: list = []
         return self._create_module_string(module)
 
     def _create_module_string(self, module: Module) -> str:
@@ -175,7 +176,8 @@ def _create_class_string(self, class_: Class, class_indentation: str = "") -> st
         constraints_info = ""
         variance_info = ""
         if class_.type_parameters:
-            variances = []
+            # We collect the class generics for the methods later
+            self.class_generics = []
             out = "out "
             for variance in class_.type_parameters:
                 variance_direction = {
@@ -189,12 +191,12 @@ def _create_class_string(self, class_: Class, class_indentation: str = "") -> st
                 variance_name_camel_case = self._replace_if_safeds_keyword(variance_name_camel_case)
 
                 variance_item = f"{variance_direction}{variance_name_camel_case}"
-                if variance_direction == out:
+                if variance.type is not None:
                     variance_item = f"{variance_item} sub {self._create_type_string(variance.type.to_dict())}"
-                variances.append(variance_item)
+                self.class_generics.append(variance_item)
 
-            if variances:
-                variance_info = f"<{', '.join(variances)}>"
+            if self.class_generics:
+                variance_info = f"<{', '.join(self.class_generics)}>"
 
         # Class name - Convert to camelCase and check for keywords
         class_name = class_.name
@@ -265,6 +267,10 @@ def _create_class_attribute_string(self, attributes: list[Attribute], inner_inde
             if attribute.type:
                 attribute_type = attribute.type.to_dict()
 
+                # Don't create TypeVar attributes
+                if attribute_type["kind"] == "TypeVarType":
+                    continue
+
             static_string = "static " if attribute.is_static else ""
 
             # Convert name to camelCase and add PythonName annotation
@@ -317,6 +323,24 @@ def _create_function_string(self, function: Function, indentations: str = "", is
             is_instance_method=not is_static and is_method,
         )
 
+        # TypeVar
+        type_var_info = ""
+        if function.type_var_types:
+            type_var_names = []
+            for type_var in function.type_var_types:
+                type_var_name = self._convert_snake_to_camel_case(type_var.name)
+                type_var_name = self._replace_if_safeds_keyword(type_var_name)
+
+                # We don't have to display generic types in methods if they were already displayed in the class
+                if not is_method or (is_method and type_var_name not in self.class_generics):
+                    if type_var.upper_bound is not None:
+                        type_var_name += f" sub {self._create_type_string(type_var.upper_bound.to_dict())}"
+                    type_var_names.append(type_var_name)
+
+            if type_var_names:
+                type_var_string = ", ".join(type_var_names)
+                type_var_info = f"<{type_var_string}>"
+
         # Convert function name to camelCase
         name = function.name
         camel_case_name = self._convert_snake_to_camel_case(name)
@@ -334,8 +358,8 @@ def _create_function_string(self, function: Function, indentations: str = "", is
             f"{self._create_todo_msg(indentations)}"
             f"{indentations}@Pure\n"
             f"{function_name_annotation}"
-            f"{indentations}{static}fun {camel_case_name}({func_params})"
-            f"{result_string}"
+            f"{indentations}{static}fun {camel_case_name}{type_var_info}"
+            f"({func_params}){result_string}"
         )
 
     def _create_property_function_string(self, function: Function, indentations: str = "") -> str:
@@ -621,9 +645,9 @@ def _create_type_string(self, type_data: dict | None) -> str:
                 else:
                     types.append(f"{literal_type}")
             return f"literal<{', '.join(types)}>"
-        # Todo See issue #63
         elif kind == "TypeVarType":
-            return ""
+            name = self._convert_snake_to_camel_case(type_data["name"])
+            return self._replace_if_safeds_keyword(name)
 
         raise ValueError(f"Unexpected type: {kind}")  # pragma: no cover
 

tests/data/various_modules_package/attribute_module.py

@@ -1,4 +1,4 @@
-from typing import Optional, Final, Literal, TypeVar
+from typing import Optional, Final, Literal
 from tests.data.main_package.another_path.another_module import AnotherClass
 
 
@@ -66,7 +66,5 @@ def some_func() -> bool:
     attr_type_from_outside_package: AnotherClass
     attr_default_value_from_outside_package = AnotherClass
 
-    type_var = TypeVar("type_var")
-
     def __init__(self):
         self.init_attr: bool = False

tests/data/various_modules_package/function_module.py

@@ -1,4 +1,4 @@
-from typing import Callable, Optional, Literal, Any, TypeVar
+from typing import Callable, Optional, Literal, Any
 from tests.data.main_package.another_path.another_module import AnotherClass
 
 
@@ -187,10 +187,6 @@ def param_from_outside_the_package(param_type: AnotherClass, param_value=Another
 def result_from_outside_the_package() -> AnotherClass: ...
 
 
-_type_var = TypeVar("_type_var")
-def type_var_func(type_var_list: list[_type_var]) -> list[_type_var]: ...
-
-
 class FunctionModulePropertiesClass:
     @property
     def property_function(self): ...

tests/data/various_modules_package/type_var_module.py

@@ -0,0 +1,30 @@
+from typing import TypeVar, Generic
+
+T = TypeVar('T')
+
+
+class TypeVarClass(Generic[T]):
+    type_var = TypeVar("type_var")
+
+    def __init__(self, items: list[T]): ...
+
+    def type_var_class_method(self, a: T) -> T: ...
+
+
+class TypeVarClass2(Generic[T]):
+    type_var = TypeVar("type_var")
+
+    def type_var_class_method2(self, a: T) -> T: ...
+
+
+_type_var = TypeVar("_type_var")
+def type_var_func(a: list[_type_var]) -> list[_type_var]: ...
+
+
+_type_var1 = TypeVar("_type_var1")
+_type_var2 = TypeVar("_type_var2")
+def multiple_type_var(a: _type_var1, b: _type_var2) -> list[_type_var1 | _type_var2]: ...
+
+
+T_in = TypeVar("T_in", bound=int)
+def type_var_fun_invariance_with_bound(a: list[T_in]) -> T_in: ...

tests/data/various_modules_package/variance_module.py

@@ -5,14 +5,27 @@ class A:
     ...
 
 
-_T_co = TypeVar("_T_co", covariant=True, bound=str)
-_T_con = TypeVar("_T_con", contravariant=True, bound=A)
-_T_in = TypeVar("_T_in", int, Literal[1, 2])
+_T_in = TypeVar("_T_in")
+_T_co = TypeVar("_T_co", covariant=True)
+_T_con = TypeVar("_T_con", contravariant=True)
 
 
-class VarianceClassAll(Generic[_T_co, _T_con, _T_in]):
+class VarianceClassOnlyCovarianceNoBound(Generic[_T_co]):
     ...
 
 
-class VarianceClassOnlyInvariance(Generic[_T_in]):
+class VarianceClassOnlyVarianceNoBound(Generic[_T_in]):
+    ...
+
+
+class VarianceClassOnlyContravarianceNoBound(Generic[_T_con]):
+    ...
+
+
+_T_co2 = TypeVar("_T_co2", covariant=True, bound=str)
+_T_con2 = TypeVar("_T_con2", contravariant=True, bound=A)
+_T_in2 = TypeVar("_T_in2", int, Literal[1, 2])
+
+
+class VarianceClassAll(Generic[_T_co2, _T_con2, _T_in2]):
     ...