Assets: ensure catalog paths for online assets do not contain a colon

The Asset Catalog definition file is colon-separated, so colons should
not appear in any of the fields themselves. Rather than adding elaborate
escaping rules, just don't write those characters.

This is just implemented for online asset listings, as that's considered
3rd-party data, and thus needs more sanitising before writing to a local
file.

Pull Request: https://projects.blender.org/blender/blender/pulls/157439

tests/python/assets/remote_library_listing/CMakeLists.txt

@@ -2,6 +2,13 @@
 #
 # SPDX-License-Identifier: GPL-2.0-or-later
 
+add_blender_test(
+  assets_remote_library_listing_asset_catalogs_test
+    --python ${CMAKE_CURRENT_LIST_DIR}/listing_asset_catalogs_test.py
+    --
+    --outdir "${TEST_OUT_DIR}/assets"
+)
+
 add_blender_test(
   assets_remote_library_listing_downloader_test
     --python ${CMAKE_CURRENT_LIST_DIR}/listing_downloader_test.py

tests/python/assets/remote_library_listing/listing_asset_catalogs_test.py

@@ -0,0 +1,98 @@
+# SPDX-FileCopyrightText: 2026 Blender Authors
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import sys
+import unittest
+from pathlib import Path
+
+from _bpy_internal.assets.remote_library_listing import listing_asset_catalogs
+from _bpy_internal.assets.remote_library_listing import blender_asset_library_openapi as api_models
+
+"""
+blender -b --factory-startup -P tests/python/assets/remote_library_listing/listing_asset_catalogs_test.py -- --outdir=/tmp
+"""
+
+# CLI argument, will be set to its actual value in main() below.
+arg_outdir: Path
+
+
+class ListingDownloaderTest(unittest.TestCase):
+    cats_path: Path
+
+    @classmethod
+    def setUpClass(cls) -> None:
+        arg_outdir.mkdir(parents=True, exist_ok=True)
+        cls.cats_path = arg_outdir / "test_catalogs.cats.txt"
+
+    def tearDown(self) -> None:
+        self.cats_path.unlink(missing_ok=True)
+
+    def test_write_sanitized_cats(self) -> None:
+        catalogs = [
+            api_models.CatalogV1(
+                path="Cats/Laksa",
+                uuids=["cdf49402-6814-5c20-a026-9f3211d8a615"],
+                simple_name="cats-laksa",
+            ),
+            api_models.CatalogV1(
+                path="Cats/Quercus\nwith\nnewlines",
+                uuids=["2143dfac-9e81-5a31-99f2-befa8ff26ac2"],
+                simple_name="cats-quercus",
+            ),
+            api_models.CatalogV1(
+                path="Cats/Raymond\n: Pawducer",
+                uuids=["db847984-cb61-5197-87b5-39134a2e758c"],
+                simple_name="cats-raymond",
+            ),
+            api_models.CatalogV1(
+                path="Cats/Muesli: Huntress",
+                uuids=["d7ce44c8-d1df-5055-bae4-8a6ed03b8329"],
+                simple_name="cats-muesli",
+            ),
+        ]
+        asset_library_meta = api_models.AssetLibraryMeta(
+            api_versions={},
+            contact=api_models.Contact(name="Unit the Tester"),
+            name="Cats of\nAmsterdam",
+        )
+
+        listing_asset_catalogs.write(catalogs, self.cats_path, asset_library_meta)
+
+        # Check the file is as expected.
+        file_lines = self.cats_path.read_text().splitlines()
+
+        # The line numbers are determined by listing_asset_catalogs._ASSET_CATS_HEADER.
+        header_num_lines = len(listing_asset_catalogs._ASSET_CATS_HEADER.splitlines())
+        self.assertIn("Cats of Amsterdam", file_lines[header_num_lines - 3])
+
+        # The catalogs should be ordered by path, and sanitized.
+        written_cats = file_lines[header_num_lines + 1:]
+        expect_cats = [
+            "cdf49402-6814-5c20-a026-9f3211d8a615:Cats/Laksa:cats-laksa",
+            "d7ce44c8-d1df-5055-bae4-8a6ed03b8329:Cats/Muesli Huntress:cats-muesli",
+            "2143dfac-9e81-5a31-99f2-befa8ff26ac2:Cats/Quercus with newlines:cats-quercus",
+            "db847984-cb61-5197-87b5-39134a2e758c:Cats/Raymond Pawducer:cats-raymond",
+        ]
+        self.assertEqual(expect_cats, written_cats)
+
+
+def main():
+    global arg_outdir
+    import argparse
+
+    argv = [sys.argv[0]]
+    if '--' in sys.argv:
+        argv += sys.argv[sys.argv.index('--') + 1:]
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--outdir', required=True, type=Path)
+    args, remaining = parser.parse_known_args(argv)
+
+    arg_outdir = args.outdir
+
+    unittest.main(argv=remaining)
+
+
+if __name__ == "__main__":
+    main()