PyAPI: use postponed annotations to support Python 3.10

Support Python 3.10a5 or 3.9x with support explicitly enabled.

- Enable Python's postponed annotations for Blender's RNA classes
  types registered on startup.

- Using postponed annotations has implications for how they are defined,
  since they must evaluate in the modules name-space instead of the
  classes name-space. See changes to annotations in `release/scripts`.

- Use `from __future__ import annotations` at the top of the module
  to ensure the script will run with Python 3.10.

- Old logic is kept since it could be used if PEP-649 is supported.

Resolves T83626

Ref D10474

intern/cycles/blender/addon/__init__.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 bl_info = {
     "name": "Cycles Render Engine",

intern/cycles/blender/addon/engine.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 
 def _is_using_buggy_driver():

intern/cycles/blender/addon/operators.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.types import Operator

intern/cycles/blender/addon/osl.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 import _cycles

intern/cycles/blender/addon/presets.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 from bl_operators.presets import AddPresetBase
 from bpy.types import Operator

intern/cycles/blender/addon/properties.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.props import (
@@ -841,7 +842,7 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
             ('MEGA', "Mega", ""),
             ('SPLIT', "Split", ""),
         ),
-        update=_devices_update_callback
+        update=CyclesRenderSettings._devices_update_callback
     )
 
     debug_opencl_device_type: EnumProperty(
@@ -855,11 +856,9 @@ class CyclesRenderSettings(bpy.types.PropertyGroup):
             ('GPU', "GPU", ""),
             ('ACCELERATOR', "Accelerator", ""),
         ),
-        update=_devices_update_callback
+        update=CyclesRenderSettings._devices_update_callback
     )
 
-    del _devices_update_callback
-
     debug_use_opencl_debug: BoolProperty(name="Debug OpenCL", default=False)
 
     debug_opencl_mem_limit: IntProperty(
@@ -1481,7 +1480,7 @@ class CyclesPreferences(bpy.types.AddonPreferences):
     compute_device_type: EnumProperty(
         name="Compute Device Type",
         description="Device to use for computation (rendering with Cycles)",
-        items=get_device_types,
+        items=CyclesPreferences.get_device_types,
     )
 
     devices: bpy.props.CollectionProperty(type=CyclesDeviceSettings)

intern/cycles/blender/addon/ui.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy_extras.node_utils import find_node_input

intern/cycles/blender/addon/version_update.py

@@ -15,6 +15,7 @@
 #
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 import math

release/scripts/modules/bpy_extras/object_utils.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 __all__ = (
     "add_object_align_init",
@@ -180,7 +181,7 @@ class AddObjectHelper:
             ('CURSOR', "3D Cursor", "Use the 3D cursor orientation for the new object"),
         ),
         default='WORLD',
-        update=align_update_callback,
+        update=AddObjectHelper.align_update_callback,
     )
     location: FloatVectorProperty(
         name="Location",

release/scripts/startup/bl_operators/__init__.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8 compliant>
+from __future__ import annotations
 
 # support reloading sub-modules
 if "bpy" in locals():

release/scripts/startup/bl_operators/add_mesh_torus.py

@@ -17,6 +17,8 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
+
 import bpy
 from bpy.types import Operator
 
@@ -156,7 +158,7 @@ class AddTorus(Operator, object_utils.AddObjectHelper):
             ('EXT_INT', "Exterior/Interior",
              "Use the exterior/interior radii for torus dimensions"),
         ),
-        update=mode_update_callback,
+        update=AddTorus.mode_update_callback,
     )
     major_radius: FloatProperty(
         name="Major Radius",

release/scripts/startup/bl_operators/anim.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 if "bpy" in locals():
     from importlib import reload

release/scripts/startup/bl_operators/assets.py

@@ -16,6 +16,9 @@
 #
 # ##### END GPL LICENSE BLOCK #####
 
+# <pep8 compliant>
+from __future__ import annotations
+
 import bpy
 
 from bpy_extras.asset_utils import (

release/scripts/startup/bl_operators/console.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.types import Operator

release/scripts/startup/bl_operators/constraint.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 from bpy.types import (
     Operator,

release/scripts/startup/bl_operators/node.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8-80 compliant>
+from __future__ import annotations
 
 import bpy
 import nodeitems_utils
@@ -218,7 +219,7 @@ class NODE_OT_add_search(NodeAddOperator, Operator):
     node_item: EnumProperty(
         name="Node Type",
         description="Node type",
-        items=node_enum_items,
+        items=NODE_OT_add_search.node_enum_items,
     )
 
     def execute(self, context):

release/scripts/startup/bl_operators/wm.py

@@ -17,6 +17,7 @@
 # ##### END GPL LICENSE BLOCK #####
 
 # <pep8 compliant>
+from __future__ import annotations
 
 import bpy
 from bpy.types import (
@@ -859,9 +860,7 @@ class WM_OT_url_open_preset(Operator):
 
     type: EnumProperty(
         name="Site",
-        items=lambda self, _context: (
-            item for (item, _) in WM_OT_url_open_preset.preset_items
-        ),
+        items=WM_OT_url_open_preset._preset_items,
     )
 
     id: StringProperty(
@@ -916,6 +915,10 @@ class WM_OT_url_open_preset(Operator):
          "https://www.blender.org/about/credits/"),
     ]
 
+    @staticmethod
+    def _preset_items(_self, _context):
+        return (item for (item, _) in WM_OT_url_open_preset.preset_items)
+
     def execute(self, context):
         url = None
         type = self.type

source/blender/python/intern/bpy_props.c

@@ -227,6 +227,20 @@ static PyObject *bpy_prop_deferred_repr(BPy_PropDeferred *self)
   return PyUnicode_FromFormat("<%.200s, %R, %R>", Py_TYPE(self)->tp_name, self->fn, self->kw);
 }
 
+/**
+ * HACK: needed by `typing.get_type_hints`
+ * with `from __future__ import annotations` enabled or when using Python 3.10 or newer.
+ *
+ * When callable this object type passes the test for being an acceptable annotation.
+ */
+static PyObject *bpy_prop_deferred_call(BPy_PropDeferred *UNUSED(self),
+                                        PyObject *UNUSED(args),
+                                        PyObject *UNUSED(kw))
+{
+  /* Dummy value. */
+  Py_RETURN_NONE;
+}
+
 /* Get/Set Items. */
 
 /**
@@ -257,7 +271,6 @@ static PyGetSetDef bpy_prop_deferred_getset[] = {
     {NULL, NULL, NULL, NULL, NULL} /* Sentinel */
 };
 
-
 PyTypeObject bpy_prop_deferred_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
 
@@ -265,6 +278,7 @@ PyTypeObject bpy_prop_deferred_Type = {
     .tp_basicsize = sizeof(BPy_PropDeferred),
     .tp_dealloc = (destructor)bpy_prop_deferred_dealloc,
     .tp_repr = (reprfunc)bpy_prop_deferred_repr,
+    .tp_call = (ternaryfunc)bpy_prop_deferred_call,
 
     .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
 

source/blender/python/intern/bpy_rna.c

@@ -80,6 +80,15 @@
 #define USE_MATHUTILS
 #define USE_STRING_COERCE
 
+/**
+ * This _must_ be enabled to support Python 3.10's postponed annotations,
+ * `from __future__ import annotations`.
+ *
+ * This has the disadvantage of evaluating strings at run-time, in the future we might be able to
+ * reinstate the older, more efficient logic using descriptors, see: pep-0649
+ */
+#define USE_POSTPONED_ANNOTATIONS
+
 /* Unfortunately Python needs to hold a global reference to the context.
  * If we remove this is means `bpy.context` won't be usable from some parts of the code:
  * `bpy.app.handler` callbacks for example.
@@ -7935,6 +7944,65 @@ static int deferred_register_prop(StructRNA *srna, PyObject *key, PyObject *item
   return 0;
 }
 
+/**
+ * Extract `__annotations__` using `typing.get_type_hints` which handles the delayed evaluation.
+ */
+static int pyrna_deferred_register_class_from_type_hints(StructRNA *srna, PyTypeObject *py_class)
+{
+  PyObject *annotations_dict = NULL;
+
+  /* `typing.get_type_hints(py_class)` */
+  {
+    PyObject *typing_mod = PyImport_ImportModuleLevel("typing", NULL, NULL, NULL, 0);
+    if (typing_mod != NULL) {
+      PyObject *get_type_hints_fn = PyObject_GetAttrString(typing_mod, "get_type_hints");
+      if (get_type_hints_fn != NULL) {
+        PyObject *args = PyTuple_New(1);
+
+        PyTuple_SET_ITEM(args, 0, (PyObject *)py_class);
+        Py_INCREF(py_class);
+
+        annotations_dict = PyObject_CallObject(get_type_hints_fn, args);
+
+        Py_DECREF(args);
+        Py_DECREF(get_type_hints_fn);
+      }
+      Py_DECREF(typing_mod);
+    }
+  }
+
+  int ret = 0;
+  if (annotations_dict != NULL) {
+    if (PyDict_CheckExact(annotations_dict)) {
+      PyObject *item, *key;
+      Py_ssize_t pos = 0;
+
+      while (PyDict_Next(annotations_dict, &pos, &key, &item)) {
+        ret = deferred_register_prop(srna, key, item);
+        if (ret != 0) {
+          break;
+        }
+      }
+    }
+    else {
+      /* Should never happen, an error wont have been raised, so raise one. */
+      PyErr_Format(PyExc_TypeError,
+                   "typing.get_type_hints returned: %.200s, expected dict\n",
+                   Py_TYPE(annotations_dict)->tp_name);
+      ret = -1;
+    }
+
+    Py_DECREF(annotations_dict);
+  }
+  else {
+    BLI_assert(PyErr_Occurred());
+    fprintf(stderr, "typing.get_type_hints failed with: %.200s\n", py_class->tp_name);
+    ret = -1;
+  }
+
+  return ret;
+}
+
 static int pyrna_deferred_register_props(StructRNA *srna, PyObject *class_dict)
 {
   PyObject *annotations_dict;
@@ -7999,6 +8067,15 @@ int pyrna_deferred_register_class(StructRNA *srna, PyTypeObject *py_class)
     return 0;
   }
 
+#ifdef USE_POSTPONED_ANNOTATIONS
+  const bool use_postponed_annotations = true;
+#else
+  const bool use_postponed_annotations = false;
+#endif
+
+  if (use_postponed_annotations) {
+    return pyrna_deferred_register_class_from_type_hints(srna, py_class);
+  }
   return pyrna_deferred_register_class_recursive(srna, py_class);
 }