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

1 files changed, 6 insertions, 3 deletions

diff --git a/release/scripts/startup/bl_operators/wm.py b/release/scripts/startup/bl_operators/wm.py
index c5457713d36..db15f4597bf 100644
--- a/release/scripts/startup/bl_operators/wm.py
+++ b/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