preliminary support for backporting to Python 3.12 and Python 3.10

unpy/_types.py

@@ -29,7 +29,7 @@
 
 class PythonVersion(tuple[int, ...], enum.ReprEnum):  # noqa: SLOT001
     # PY39 = (3, 9)
-    # PY310 = (3, 10)
+    PY310 = (3, 10)
     PY311 = (3, 11)
     PY312 = (3, 12)
     # PY313 = (3, 13)

unpy/transformers.py

@@ -136,6 +136,15 @@ def visit_Module(self, /, node: cst.Module) -> None:
         visitor = self.visitor
         target = self.target
 
+        if target >= (3, 12):
+            # PEP 695 makes these redundant
+            for tvar_name in ["TypeVar", "TypeVarTuple", "ParamSpec"]:
+                visitor.imports_add.discard(f"typing.{tvar_name}")
+        if target >= (3, 13):
+            # PEP 695 & PEP 696 make these redundant
+            visitor.imports_add.clear()
+            visitor.imports_del.clear()
+
         for fqn in visitor.imports:
             if "." not in fqn or fqn.startswith(".") or fqn.endswith("*"):
                 continue
@@ -256,6 +265,11 @@ def leave_FunctionDef(
     ) -> cst.FunctionDef | cst.FlattenSentinel[cst.BaseStatement]:
         self._stack.pop()
 
+        if not (tpars := updated_node.type_parameters):
+            return updated_node
+        if self.target >= (3, 12) and not any(tpar.default for tpar in tpars.params):
+            return updated_node
+
         updated_node = _remove_tpars(updated_node)
         return updated_node if self._stack else self._prepend_tvars(updated_node)
 
@@ -274,6 +288,8 @@ def leave_ClassDef(
 
         if not (tpars := original_node.type_parameters):
             return updated_node
+        if self.target >= (3, 12) and not any(tpar.default for tpar in tpars.params):
+            return updated_node
 
         base_args = updated_node.bases
         tpar_names = (tpar.param.name for tpar in tpars.params)
@@ -304,6 +320,8 @@ def leave_ClassDef(
             expr_generic = parse_name(name_generic or "Generic")
             new_bases.insert(i, cst.Arg(parse_subscript(expr_generic, *tpar_names)))
 
+            visitor.desire_import("typing", "Generic", has_backport=True)
+
         updated_node = updated_node.with_changes(type_parameters=None, bases=new_bases)
 
         stack.pop()
@@ -374,6 +392,4 @@ def transform_source(
     *,
     target: PythonVersion = PythonVersion.PY311,
 ) -> str:
-    if target != PythonVersion.PY311:
-        raise NotImplementedError(f"Python {target}")
     return transform_module(cst.parse_module(source), target=target).code

unpy/visitors.py

@@ -482,9 +482,6 @@ def visit_ClassDef(self, /, node: cst.ClassDef) -> None:
             )
 
         if tpars := node.type_parameters:
-            if self.imported_from_typing_as("Protocol") not in base_set:
-                self.desire_import("typing", "Generic", has_backport=True)
-
             self._register_type_params(stack[0], tpars, variant=True)
 
     @override