Steps to reproduce

1. Install dependencies

cd books-service && npm install then cd gateway && npm install

2. Compile & run books service

cd books-service
npm run webpack
node dist/index.js

Will bind to port 4000

4. Compile & run gateway

cd gateway
npm run webpack
node dist/index.js

Will bind to port 4001

5. Hit the mutation on the gateway

Navigate to http://localhost:4001 and create a mutation against addBook.

Alternatively, this curl should do it:

curl --request POST \
    --header 'content-type: application/json' \
    --url http://localhost:4001/ \
    --data '{"query":"mutation Mutation($book: BookInput!) {\n  addBook(book: $book) {\n    author\n    title\n  }\n}","variables":{"book":{"author":"a","title":"t"}}}' | jq

Expected behavior: should return a 200 with an empty data field like this:

{
  "data": {
    "addBook": null
  }
}

Instead, it errors out with an invalid signature error such as this:

{
  "errors": [
    {
      "message": "Expected BookInput to be a GraphQL nullable type.",
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "stacktrace": [
          "Error: Expected BookInput to be a GraphQL nullable type.",
          "    at t.devAssert (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:908657)",
          "    at new F (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:936793)",
          "    at e (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:989183)",
          "    at /home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:905991",
          "    at t.getVariableValues (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:906849)",
          "    at /home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:383674",
          "    at e.with (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:579891)",
          "    at e.with (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:580943)",
          "    at e.startActiveSpan (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:583455)",
          "    at e.startActiveSpan (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:583753)",
          "    at T.validateIncomingRequest (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:383521)",
          "    at /home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:370765",
          "    at e.with (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:579891)",
          "    at e.with (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:580943)",
          "    at e.startActiveSpan (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:583455)",
          "    at e.startActiveSpan (/home/luchini/repos/experiments/webpack-bug/gateway/dist/index.js:2:583753)"
        ]
      }
    }
  ]
}

---

Sanity checks

A) Run same query against books service

Navigate to http://localhost:4000 and create a mutation against addBook.

Alternatively, this curl should do it:

curl --request POST \
    --header 'content-type: application/json' \
    --url http://localhost:4000/ \
    --data '{"query":"mutation Mutation($book: BookInput!) {\n  addBook(book: $book) {\n    author\n    title\n  }\n}","variables":{"book":{"author":"a","title":"t"}}}' | jq

Books service should work as expected above. This is proof that the underlying service is working and that the gateway should did not rout the mutation request to the service.

B) Run gateway in our development config

Replace step 4 above with:

cd gateway
npm run webpack:dev
node dist/index.js

Try step 5 above again against the new gateway running on port 4001 and it will work as expected.