gh-119180: Add evaluate functions for type params and type aliases (#122212)

Author: JelleZijlstra

Include/internal/pycore_global_objects.h

@@ -81,6 +81,7 @@ struct _Py_interp_cached_objects {
     PyTypeObject *paramspec_type;
     PyTypeObject *paramspecargs_type;
     PyTypeObject *paramspeckwargs_type;
+    PyTypeObject *constevaluator_type;
 };
 
 #define _Py_INTERP_STATIC_OBJECT(interp, NAME) \

Include/internal/pycore_typevarobject.h

@@ -16,6 +16,7 @@ extern PyObject *_Py_subscript_generic(PyThreadState *, PyObject *);
 extern PyObject *_Py_set_typeparam_default(PyThreadState *, PyObject *, PyObject *);
 extern int _Py_initialize_generic(PyInterpreterState *);
 extern void _Py_clear_generic_types(PyInterpreterState *);
+extern int _Py_typing_type_repr(PyUnicodeWriter *, PyObject *);
 
 extern PyTypeObject _PyTypeAlias_Type;
 extern PyTypeObject _PyNoDefault_Type;

Lib/annotationlib.py

@@ -413,7 +413,16 @@ def __missing__(self, key):
         return fwdref
 
 
-def call_annotate_function(annotate, format, owner=None):
+def call_evaluate_function(evaluate, format, *, owner=None):
+    """Call an evaluate function. Evaluate functions are normally generated for
+    the value of type aliases and the bounds, constraints, and defaults of
+    type parameter objects.
+    """
+    return call_annotate_function(evaluate, format, owner=owner, _is_evaluate=True)
+
+
+def call_annotate_function(annotate, format, *, owner=None,
+                           _is_evaluate=False):
     """Call an __annotate__ function. __annotate__ functions are normally
     generated by the compiler to defer the evaluation of annotations. They
     can be called with any of the format arguments in the Format enum, but
@@ -459,8 +468,11 @@ def call_annotate_function(annotate, format, owner=None):
             closure = tuple(new_closure)
         else:
             closure = None
-        func = types.FunctionType(annotate.__code__, globals, closure=closure)
+        func = types.FunctionType(annotate.__code__, globals, closure=closure,
+                                  argdefs=annotate.__defaults__, kwdefaults=annotate.__kwdefaults__)
         annos = func(Format.VALUE)
+        if _is_evaluate:
+            return annos if isinstance(annos, str) else repr(annos)
         return {
             key: val if isinstance(val, str) else repr(val)
             for key, val in annos.items()
@@ -511,7 +523,8 @@ def call_annotate_function(annotate, format, owner=None):
             closure = tuple(new_closure)
         else:
             closure = None
-        func = types.FunctionType(annotate.__code__, globals, closure=closure)
+        func = types.FunctionType(annotate.__code__, globals, closure=closure,
+                                  argdefs=annotate.__defaults__, kwdefaults=annotate.__kwdefaults__)
         result = func(Format.VALUE)
         for obj in globals.stringifiers:
             obj.__class__ = ForwardRef

Lib/test/test_annotationlib.py

@@ -773,6 +773,25 @@ def test_pep_695_generics_with_future_annotations_nested_in_function(self):
         )
 
 
+class TestCallEvaluateFunction(unittest.TestCase):
+    def test_evaluation(self):
+        def evaluate(format, exc=NotImplementedError):
+            if format != 1:
+                raise exc
+            return undefined
+
+        with self.assertRaises(NameError):
+            annotationlib.call_evaluate_function(evaluate, annotationlib.Format.VALUE)
+        self.assertEqual(
+            annotationlib.call_evaluate_function(evaluate, annotationlib.Format.FORWARDREF),
+            annotationlib.ForwardRef("undefined"),
+        )
+        self.assertEqual(
+            annotationlib.call_evaluate_function(evaluate, annotationlib.Format.SOURCE),
+            "undefined",
+        )
+
+
 class MetaclassTests(unittest.TestCase):
     def test_annotated_meta(self):
         class Meta(type):

Lib/test/test_type_params.py

@@ -1,3 +1,4 @@
+import annotationlib
 import asyncio
 import textwrap
 import types
@@ -6,7 +7,7 @@
 import weakref
 from test.support import requires_working_socket, check_syntax_error, run_code
 
-from typing import Generic, NoDefault, Sequence, TypeVar, TypeVarTuple, ParamSpec, get_args
+from typing import Generic, NoDefault, Sequence, TypeAliasType, TypeVar, TypeVarTuple, ParamSpec, get_args
 
 
 class TypeParamsInvalidTest(unittest.TestCase):
@@ -1394,3 +1395,43 @@ def test_symtable_key_regression_name(self):
 
         self.assertEqual(ns["X1"].__type_params__[0].__default__, "A")
         self.assertEqual(ns["X2"].__type_params__[0].__default__, "B")
+
+
+class TestEvaluateFunctions(unittest.TestCase):
+    def test_general(self):
+        type Alias = int
+        Alias2 = TypeAliasType("Alias2", int)
+        def f[T: int = int, **P = int, *Ts = int](): pass
+        T, P, Ts = f.__type_params__
+        T2 = TypeVar("T2", bound=int, default=int)
+        P2 = ParamSpec("P2", default=int)
+        Ts2 = TypeVarTuple("Ts2", default=int)
+        cases = [
+            Alias.evaluate_value,
+            Alias2.evaluate_value,
+            T.evaluate_bound,
+            T.evaluate_default,
+            P.evaluate_default,
+            Ts.evaluate_default,
+            T2.evaluate_bound,
+            T2.evaluate_default,
+            P2.evaluate_default,
+            Ts2.evaluate_default,
+        ]
+        for case in cases:
+            with self.subTest(case=case):
+                self.assertIs(case(1), int)
+                self.assertIs(annotationlib.call_evaluate_function(case, annotationlib.Format.VALUE), int)
+                self.assertIs(annotationlib.call_evaluate_function(case, annotationlib.Format.FORWARDREF), int)
+                self.assertEqual(annotationlib.call_evaluate_function(case, annotationlib.Format.SOURCE), 'int')
+
+    def test_constraints(self):
+        def f[T: (int, str)](): pass
+        T, = f.__type_params__
+        T2 = TypeVar("T2", int, str)
+        for case in [T, T2]:
+            with self.subTest(case=case):
+                self.assertEqual(case.evaluate_constraints(1), (int, str))
+                self.assertEqual(annotationlib.call_evaluate_function(case.evaluate_constraints, annotationlib.Format.VALUE), (int, str))
+                self.assertEqual(annotationlib.call_evaluate_function(case.evaluate_constraints, annotationlib.Format.FORWARDREF), (int, str))
+                self.assertEqual(annotationlib.call_evaluate_function(case.evaluate_constraints, annotationlib.Format.SOURCE), '(int, str)')

Misc/NEWS.d/next/Library/2024-07-23-22-26-00.gh-issue-119180.B2IVT8.rst

@@ -0,0 +1,7 @@
+As part of :pep:`749`, add the following attributes for customizing
+evaluation of annotation scopes:
+
+* ``evaluate_value`` on :class:`typing.TypeAliasType`
+* ``evaluate_bound``, ``evaluate_constraints``, and ``evaluate_default`` on :class:`typing.TypeVar`
+* ``evaluate_default`` on :class:`typing.ParamSpec`
+* ``evaluate_default`` on :class:`typing.TypeVarTuple`

Objects/genericaliasobject.c

@@ -4,6 +4,7 @@
 #include "pycore_ceval.h"         // _PyEval_GetBuiltin()
 #include "pycore_modsupport.h"    // _PyArg_NoKeywords()
 #include "pycore_object.h"
+#include "pycore_typevarobject.h" // _Py_typing_type_repr
 #include "pycore_unionobject.h"   // _Py_union_type_or, _PyGenericAlias_Check
 
 
@@ -50,69 +51,6 @@ ga_traverse(PyObject *self, visitproc visit, void *arg)
     return 0;
 }
 
-static int
-ga_repr_item(PyUnicodeWriter *writer, PyObject *p)
-{
-    PyObject *qualname = NULL;
-    PyObject *module = NULL;
-    int rc;
-
-    if (p == Py_Ellipsis) {
-        // The Ellipsis object
-        rc = PyUnicodeWriter_WriteUTF8(writer, "...", 3);
-        goto done;
-    }
-
-    if ((rc = PyObject_HasAttrWithError(p, &_Py_ID(__origin__))) > 0 &&
-        (rc = PyObject_HasAttrWithError(p, &_Py_ID(__args__))) > 0)
-    {
-        // It looks like a GenericAlias
-        goto use_repr;
-    }
-    if (rc < 0) {
-        goto error;
-    }
-
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__qualname__), &qualname) < 0) {
-        goto error;
-    }
-    if (qualname == NULL) {
-        goto use_repr;
-    }
-    if (PyObject_GetOptionalAttr(p, &_Py_ID(__module__), &module) < 0) {
-        goto error;
-    }
-    if (module == NULL || module == Py_None) {
-        goto use_repr;
-    }
-
-    // Looks like a class
-    if (PyUnicode_Check(module) &&
-        _PyUnicode_EqualToASCIIString(module, "builtins"))
-    {
-        // builtins don't need a module name
-        rc = PyUnicodeWriter_WriteStr(writer, qualname);
-        goto done;
-    }
-    else {
-        rc = PyUnicodeWriter_Format(writer, "%S.%S", module, qualname);
-        goto done;
-    }
-
-error:
-    rc = -1;
-    goto done;
-
-use_repr:
-    rc = PyUnicodeWriter_WriteRepr(writer, p);
-    goto done;
-
-done:
-    Py_XDECREF(qualname);
-    Py_XDECREF(module);
-    return rc;
-}
-
 static int
 ga_repr_items_list(PyUnicodeWriter *writer, PyObject *p)
 {
@@ -131,7 +69,7 @@ ga_repr_items_list(PyUnicodeWriter *writer, PyObject *p)
             }
         }
         PyObject *item = PyList_GET_ITEM(p, i);
-        if (ga_repr_item(writer, item) < 0) {
+        if (_Py_typing_type_repr(writer, item) < 0) {
             return -1;
         }
     }
@@ -162,7 +100,7 @@ ga_repr(PyObject *self)
             goto error;
         }
     }
-    if (ga_repr_item(writer, alias->origin) < 0) {
+    if (_Py_typing_type_repr(writer, alias->origin) < 0) {
         goto error;
     }
     if (PyUnicodeWriter_WriteChar(writer, '[') < 0) {
@@ -181,7 +119,7 @@ ga_repr(PyObject *self)
                 goto error;
             }
         }
-        else if (ga_repr_item(writer, p) < 0) {
+        else if (_Py_typing_type_repr(writer, p) < 0) {
             goto error;
         }
     }