Cached REST-Response does not contain URL

[marhaupe]

I use apollo-datasource-rest to cache responses from remote REST-APIs. Responses that have a 404 status get cached and thus read from cached on subsequent calls to that same endpoint. This is fine, until the error for the request gets created. The first request - the one that actually hit the remote and not the cache - creates an error like this:

      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "response": {
          "url": "http://localhost:4000/someResource",
          "status": 404,
          "statusText": "Not Found",
          "body": "Not found"
        },
        "exception": {
          "stacktrace": [
            "Error: 404: Not Found",
            "    at ExampleDataSource.<anonymous> (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:84:25)",
            "    at Generator.next (<anonymous>)",
            "    at /sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:8:71",
            "    at new Promise (<anonymous>)",
            "    at __awaiter (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:4:12)",
            "    at ExampleDataSource.errorFromResponse (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:74:16)",
            "    at ExampleDataSource.<anonymous> (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:52:34)",
            "    at Generator.next (<anonymous>)",
            "    at /sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:8:71",
            "    at new Promise (<anonymous>)"
          ]
        }
      }

The important bit is the url-field telling us which exact request failed. The actual issue lies in the second request - the one that hits the cache -, which creates the following error:

      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "response": {
          "status": 404,
          "statusText": "Not Found",
          "body": "Not found"
        },
        "exception": {
          "stacktrace": [
            "Error: 404: Not Found",
            "    at ExampleDataSource.<anonymous> (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:84:25)",
            "    at Generator.next (<anonymous>)",
            "    at /sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:8:71",
            "    at new Promise (<anonymous>)",
            "    at __awaiter (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:4:12)",
            "    at ExampleDataSource.errorFromResponse (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:74:16)",
            "    at ExampleDataSource.<anonymous> (/sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:52:34)",
            "    at Generator.next (<anonymous>)",
            "    at /sandbox/node_modules/apollo-datasource-rest/dist/RESTDataSource.js:8:71",
            "    at new Promise (<anonymous>)"
          ]
        }
      }

As you can see, the url-field is missing. Interestingly enough, this only happens if i set a ttl in the RequestInit object I pass to the datasource. I prepared a small reproduction for this issue: https://codesandbox.io/s/little-microservice-hm0sv

I analyzed the source and believe the line causing the issue is this one: https://github.com/apollographql/apollo-server/blob/c177acd7959aaf516f8ac814f1a6bb2e6d3ed2e6/packages/apollo-datasource-rest/src/HTTPCache.ts#L60
Before spending too much time looking for possible solutions, I wanted to make sure that this is in fact an issue and not something you actually intended because of some piece of information that I'm currently missing.

[marhaupe]

Cheers!