Also handle resource resolver errors gracefully in the GracefulResourceRenderer.

Author: thet

CHANGES.rst

@@ -4,6 +4,9 @@ Changelog
 1.3 (unreleased)
 ----------------
 
+- Also handle resource resolver errors gracefully in the GracefulResourceRenderer.
+  [thet]
+
 - Improve error messages by including more detailed information.
   [thet]
 

webresource/_api.py

@@ -740,7 +740,19 @@ class GracefulResourceRenderer(ResourceRenderer):
 
     def render(self):
         lines = []
-        for resource in self.resolver.resolve():
+        resources = []
+
+        try:
+            resources = self.resolver.resolve()
+        except (
+            ResourceConflictError,
+            ResourceCircularDependencyError,
+            ResourceMissingDependencyError,
+        ) as e:
+            error_message = str(e)
+            logger.exception(error_message)
+
+        for resource in resources:
             error_message = None
             try:
                 lines.append(resource.render(self.base_url))

webresource/tests.py

@@ -811,6 +811,35 @@ def test_GracefulResourceRenderer(self):
             """<!-- File not found for resource <ScriptResource name="js2", depends="['js']"> - details in logs -->"""
         ))
 
+    def test_GreacefulResourceRenderer_resolver_errors(self):
+        # Get log level to restore it later
+        import logging
+        original_log_level = logging.getLogger().getEffectiveLevel()
+
+        # Create a resource with a circular dependency
+        resource = Resource(name='res1', resource='res1.ext', depends='res1')
+
+        resolver = wr.ResourceResolver([resource])
+        renderer = wr.GracefulResourceRenderer(resolver)
+
+        rendered = None
+        try:
+            # Supress error traceback in logs
+            logging.disable(logging.CRITICAL)
+            rendered = renderer.render()
+            # Restore logging level
+            logging.disable(original_log_level)
+        except wr.ResourceCircularDependencyError:  # pragma: nocover
+            self.fail(
+                'GracefulResourceRenderer should not raise '
+                'ResourceCircularDependencyError'
+            )
+
+        # No error is raised, but rendered is also empty.
+        # However, a server rendered HTML based UI form should still be
+        # interactible.
+        self.assertEqual(rendered, "")
+
 
 if __name__ == '__main__':
     unittest.main()