RNA: Add basic tests for the path_from_id() function.

Simply load factory startup file, and recursively iterate over
all (valid) `POINTER` and `COLLECTION` properties of all IDs.

NOTE: A few cases are currently returning invalid rna paths (at least
from quick look), these are skipped for now.

Pull Request: https://projects.blender.org/blender/blender/pulls/132809

tests/python/CMakeLists.txt

@@ -237,6 +237,11 @@ add_blender_test(
   --python ${CMAKE_CURRENT_LIST_DIR}/bl_id_management.py
 )
 
+add_blender_test(
+  bl_rna_paths
+  --python ${CMAKE_CURRENT_LIST_DIR}/bl_rna_paths.py
+)
+
 # ------------------------------------------------------------------------------
 # BLEND IO & LINKING
 

tests/python/bl_rna_paths.py

@@ -0,0 +1,83 @@
+# SPDX-FileCopyrightText: 2025 Blender Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+
+import bpy
+import unittest
+
+
+def process_rna_struct(self, struct, rna_path):
+    # These paths are currently known failures of `path_from_id`.
+    KNOWN_FAILURES = {
+        "view_settings",
+        "display_settings",
+        "colorspace_settings",
+        "render.views[\"left\"]",
+        "render.views[\"right\"]",
+        "display_settings",
+        "colorspace_settings",
+        "uv_layers[\"UVMap\"]",
+        "uv_layers[\"UVMap\"]",
+    }
+    SKIP_KNOWN_FAILURES = True
+
+    def filter_prop_iter(struct):
+        for p in struct.bl_rna.properties:
+            # Internal rna meta-data, not expected to support RNA paths generation.
+            if p.identifier in {"bl_rna", "rna_type"}:
+                continue
+            # Only these types can point to sub-structs.
+            if p.type not in {'POINTER', 'COLLECTION'}:
+                continue
+            # TODO: Dynamic typed pointer/collection properties are ignored for now.
+            if not p.fixed_type:
+                continue
+            if bpy.types.ID.bl_rna in {p.fixed_type, p.fixed_type.base}:
+                continue
+            yield p
+
+    def validate_rna_path(self, struct, rna_path_root, p, p_data, p_keys=[]):
+        if not p_data:
+            return None
+        rna_path_references = [rna_path_root + "." + p.identifier if rna_path_root else p.identifier]
+        if p_keys:
+            rna_path_reference = rna_path_references[0]
+            rna_path_references = [rna_path_reference + '[' + p_key + ']' for p_key in p_keys]
+        try:
+            rna_path_generated = p_data.path_from_id()
+        except ValueError:
+            return None
+        if SKIP_KNOWN_FAILURES and rna_path_generated in KNOWN_FAILURES:
+            return None
+        self.assertTrue((rna_path_generated in rna_path_references) or ("..." in rna_path_generated),
+                        msg=f"\"{rna_path_generated}\" (from {struct}) failed to match expected paths {rna_path_references}")
+        return rna_path_generated
+
+    for p in filter_prop_iter(struct):
+        if p.type == 'COLLECTION':
+            for p_idx, (p_key, p_data) in enumerate(getattr(struct, p.identifier).items()):
+                p_keys = ['"' + p_key + '"', str(p_idx)] if isinstance(p_key, str) else [str(p_key), str(p_idx)]
+                rna_path_sub = validate_rna_path(self, struct, rna_path, p, p_data, p_keys)
+                if rna_path_sub is not None:
+                    process_rna_struct(self, p_data, rna_path_sub)
+        else:
+            assert (p.type == 'POINTER')
+            p_data = getattr(struct, p.identifier)
+            rna_path_sub = validate_rna_path(self, struct, rna_path, p, p_data)
+            if rna_path_sub is not None:
+                process_rna_struct(self, p_data, rna_path_sub)
+
+
+# Walk over all exposed RNA properties in factory startup file, and compare generated RNA paths to 'actual' paths.
+class TestRnaPaths(unittest.TestCase):
+    def test_paths_generation(self):
+        bpy.ops.wm.read_factory_settings()
+        for data_block in bpy.data.user_map().keys():
+            process_rna_struct(self, data_block, "")
+
+
+if __name__ == '__main__':
+    import sys
+    sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else [])
+    unittest.main()