[IMP] test_themes: add test to detect accidental cross-theme references

This commit adds a test to ensure that assets and images referenced from
a theme do actually belong to that theme.

task-4146886

Part-of: odoo/design-themes#889
Signed-off-by: Arthur Detroux (ard) <ard@odoo.com>

test_themes/tests/test_theme_scope.py

@@ -0,0 +1,34 @@
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+import logging
+
+from odoo.tests import tagged, TransactionCase
+
+_logger = logging.getLogger(__name__)
+
+@tagged('post_install', '-at_install')
+class TestThemeScope(TransactionCase):
+
+    def test_scope(self):
+        websites_themes = self.env['website'].get_test_themes_websites()
+        assets_count = 0
+        attachments_count = 0
+        fails = []
+        for website in websites_themes:
+            prefix = f'{website.theme_id.name}/'
+            slash_prefix = f'/{website.theme_id.name}/'
+            theme_module = self.env['ir.module.module'].search([
+                ('name', '=', website.theme_id.name),
+            ])
+            assets = theme_module._get_module_data('ir.asset')
+            for asset in assets:
+                if not asset.path.startswith(prefix) and not asset.path.startswith(slash_prefix):
+                    fails.append(f"Asset {asset.id} {asset.key} references outside of theme {website.theme_id.name}: {asset.path}")
+            assets_count += len(assets)
+            attachments = theme_module._get_module_data('ir.attachment')
+            for attachment in attachments:
+                if not attachment.url.startswith(slash_prefix):
+                    fails.append(f"Attachment {attachment.id} {attachment.key} references outside of theme {website.theme_id.name}: {attachment.url}")
+            attachments_count += len(attachments)
+        _logger.info(f"Verified {assets_count} assets and {attachments_count} attachments")
+        self.assertFalse(fails, "\n".join(fails))