Include base_url at start of kernelspec resources path

jupyter_server/gateway/managers.py

@@ -200,9 +200,28 @@ def _get_endpoint_for_user_filter(default_endpoint):
             return "?user=".join([default_endpoint, kernel_user])
         return default_endpoint
 
+    def _replace_path_kernelspec_resources(self, kernel_specs):
+        """Helper method that replaces any gateway base_url with the server's base_url
+        This enables clients to properly route through jupyter_server to a gateway
+        for kernel resources such as logo files
+        """
+        kernelspecs = kernel_specs["kernelspecs"]
+        for kernel_name in kernelspecs:
+            resources = kernelspecs[kernel_name]["resources"]
+            for resource_name in resources:
+                original_path = resources[resource_name]
+                split_eg_base_url = str.rsplit(original_path, sep="/kernelspecs/", maxsplit=1)
+                kernel_specs["kernelspecs"][kernel_name]["resources"][
+                    resource_name
+                ] = url_path_join(self.parent.base_url, "/kernelspecs", split_eg_base_url[1])
+                self.log.debug(
+                    f"Replaced original kernel resource path {original_path} with new "
+                    f"path {kernel_specs['kernelspecs'][kernel_name]['resources'][resource_name]}"
+                )
+        return kernel_specs
+
     def _get_kernelspecs_endpoint_url(self, kernel_name=None):
         """Builds a url for the kernels endpoint
-
         Parameters
         ----------
         kernel_name : kernel name (optional)
@@ -237,6 +256,7 @@ async def list_kernel_specs(self):
         self.log.debug(f"Request list kernel specs at: {kernel_spec_url}")
         response = await gateway_request(kernel_spec_url, method="GET")
         kernel_specs = json_decode(response.body)
+        kernel_specs = self._replace_path_kernelspec_resources(kernel_specs)
         return kernel_specs
 
     async def get_kernel_spec(self, kernel_name, **kwargs):

tests/test_gateway.py

@@ -38,7 +38,11 @@ def generate_kernelspec(name):
             "metadata": {},
         }
     }
-    kernelspec_stanza = {"name": name, "spec": spec_stanza, "resources": {}}
+    kernelspec_stanza = {
+        "name": name,
+        "spec": spec_stanza,
+        "resources": {"logo-64x64": f"f/kernelspecs/{name}/logo-64x64.png"},
+    }
     return kernelspec_stanza