Fix T63892: Tools cannot be registered into some contexts (e.g.

PAINT_TEXTURE)

This fails because some tool contexts define their tools with functions
[see the following list for context that fail]:

- PARTICLE (_defs_particle.generate_from_brushes)
- SCULPT (_defs_sculpt.generate_from_brushes)
- PAINT_TEXTURE (_defs_texture_paint.generate_from_brushes)
- PAINT_VERTEX (_defs_vertex_paint.generate_from_brushes)
- PAINT_WEIGHT (_defs_weight_paint.generate_from_brushes)
- PAINT_GPENCIL (_defs_gpencil_paint.generate_from_brushes)
- SCULPT_GPENCIL (_defs_gpencil_sculpt.generate_from_brushes)
- WEIGHT_GPENCIL (_defs_gpencil_weight.generate_from_brushes)

ToolSelectPanelHelper._tools_flatten() is usually called with
cls.tools_from_context(context) [that already yields from the function].
But when registering a tool, _tools_flatten() will still give back this
function, not a ToolDef - and we cannot get a bl_idname from that.
Now check for this and yield None in that case.

Also share logic across all tool_flatten functions:
- _tools_flatten
- _tools_flatten_with_tool_index
- _tools_flatten_with_keymap

Maniphest Tasks: T63892

Differential Revision: https://developer.blender.org/D6763

release/scripts/startup/bl_ui/space_toolsystem_common.py

@@ -216,29 +216,52 @@ class ToolSelectPanelHelper:
         else:
             return 0
 
+    # tool flattening
+    #
+    # usually 'tools' is already expanded into ToolDef
+    # but when registering a tool, this can still be a function
+    # (_tools_flatten is usually called with cls.tools_from_context(context)
+    # [that already yields from the function])
+    # so if item is still a function (e.g._defs_XXX.generate_from_brushes)
+    # seems like we cannot expand here (have no context yet)
+    # if we yield None here, this will risk running into duplicate tool bl_idname [in register_tool()]
+    # but still better than erroring out
     @staticmethod
     def _tools_flatten(tools):
-        for item in tools:
+        for item_parent in tools:
-            if type(item) is tuple:
+            if item_parent is None:
-                yield from item
+                yield None
+            for item in item_parent if (type(item_parent) is tuple) else (item_parent,):
+                if item is None or _item_is_fn(item):
+                    yield None
                 else:
-                # May be None.
                     yield item
 
     @staticmethod
     def _tools_flatten_with_tool_index(tools):
-        for item in tools:
+        for item_parent in tools:
-            if type(item) is tuple:
+            if item_parent is None:
+                yield None, -1
             i = 0
-                for sub_item in item:
+            for item in item_parent if (type(item_parent) is tuple) else (item_parent,):
-                    if sub_item is None:
+                if item is None or _item_is_fn(item):
                     yield None, -1
                 else:
-                        yield sub_item, i
+                    yield item, i
                     i += 1
-            else:
+
-                # May be None.
+    # Special internal function, gives use items that contain keymaps.
-                yield item, -1
+    @staticmethod
+    def _tools_flatten_with_keymap(tools):
+        for item_parent in tools:
+            if item_parent is None:
+                continue
+            for item in item_parent if (type(item_parent) is tuple) else (item_parent,):
+                # skip None or generator function
+                if item is None or _item_is_fn(item):
+                    continue
+                if item.keymap is not None:
+                    yield item
 
     @classmethod
     def _tool_get_active(cls, context, space_type, mode, with_icon=False):
@@ -413,19 +436,6 @@ class ToolSelectPanelHelper:
             keymap_fn[0](km)
         keymap_fn[0] = km.name
 
-    # Special internal function, gives use items that contain keymaps.
-    @staticmethod
-    def _tools_flatten_with_keymap(tools):
-        for item_parent in tools:
-            if item_parent is None:
-                continue
-            for item in item_parent if (type(item_parent) is tuple) else (item_parent,):
-                # skip None or generator function
-                if item is None or _item_is_fn(item):
-                    continue
-                if item.keymap is not None:
-                    yield item
-
     @classmethod
     def register(cls):
         wm = bpy.context.window_manager