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2.x - Aliases do not work with default resolvers in merged schemas

See original GitHub issue

I opened an issue on graphql-js: https://github.com/graphql/graphql-js/issues/1530#event-1862105684

Comment by Dan https://github.com/apollographql/apollo-server/issues/1724#issuecomment-425596109

This issues doesn’t seem to be related to fragments. Aliases do not appear to be working with default resolvers in merged schemas:

OP:

Basically, when using fragments in a hierarchy like the below query, aliases don’t work and can return non-nullable errors or they simply just cause the objects to be null.

It appears that my issue may not be related to the parser itself. This is a bug that was introduced when I upgraded to Apollo Server 2.x. I even rolled back every package except apollo-server to what I had before and the issue persists.

Playground: https://pinto-hip.glitch.me

Issue the query:

{
  books {
    name
    categoryHierarchy {
      ...category
      categories {
        ...category
      }
    }
  }
}

fragment category on Category {
  abc: name
}

Error:

{
  "data": {
    "books": [
      {
        "name": "Harry Potter and the Chamber of Secrets",
        "categoryHierarchy": [
          null
        ]
      },
      {
        "name": "Jurassic Park",
        "categoryHierarchy": [
          null
        ]
      }
    ]
  },
  "errors": [
    {
      "message": "Expected Iterable, but did not find one for field Category.categories.",
      "locations": [
        {
          "line": 6,
          "column": 7
        }
      ],
      "path": [
        "books",
        0,
        "categoryHierarchy",
        0,
        "categories"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "Error: Expected Iterable, but did not find one for field Category.categories.",
            "    at invariant (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/jsutils/invariant.js:19:11)",
            "    at completeListValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:673:65)",
            "    at completeValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:643:12)",
            "    at completeValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:629:21)",
            "    at completeValueWithLocatedError (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:580:21)",
            "    at completeValueCatchingError (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:550:12)",
            "    at resolveField (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:497:10)",
            "    at /rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:364:18",
            "    at Array.reduce (<anonymous>)",
            "    at executeFields (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:361:42)"
          ]
        }
      }
    },
    {
      "message": "Expected Iterable, but did not find one for field Category.categories.",
      "locations": [
        {
          "line": 6,
          "column": 7
        }
      ],
      "path": [
        "books",
        1,
        "categoryHierarchy",
        0,
        "categories"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "Error: Expected Iterable, but did not find one for field Category.categories.",
            "    at invariant (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/jsutils/invariant.js:19:11)",
            "    at completeListValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:673:65)",
            "    at completeValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:643:12)",
            "    at completeValue (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:629:21)",
            "    at completeValueWithLocatedError (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:580:21)",
            "    at completeValueCatchingError (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:550:12)",
            "    at resolveField (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:497:10)",
            "    at /rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:364:18",
            "    at Array.reduce (<anonymous>)",
            "    at executeFields (/rbd/pnpm-volume/0897a123-e913-41b8-a689-0921f96aa33a/node_modules/.registry.npmjs.org/graphql/0.13.2/node_modules/graphql/execution/execute.js:361:42)"
          ]
        }
      }
    }
  ]
}

Issue Analytics

State:
Created 5 years ago
Comments:12

Top GitHub Comments

1reaction

dncrewscommented, Sep 28, 2018

This issues doesn’t seem to be related to fragments. Aliases do not appear to be working with default resolvers in merged schemas:

This doesn’t work:

  const typeDefs = gql`
    type Query {
      book: Book
    }

    type Book {
      category: String!
    }
  `;

  const schema = makeExecutableSchema({ typeDefs });

  const resolvers = {
    Query: {
      book: () => ({ category: 'Test' })
    }
  };

  const server = new ApolloServer({
    schema: mergeSchemas({
      schemas: [ schema ],
      resolvers
    }),
  });

This does:

  const typeDefs = gql`
    type Query {
      book: Book
    }

    type Book {
      category: String!
    }
  `;

  const schema = makeExecutableSchema({ typeDefs });

  const resolvers = {
    Query: {
      book: () => ({ category: 'Test' })
    },
    Book: {
      category: (parent) => parent.category // Adding default resolver to fix bug
    }
  };

  const server = new ApolloServer({
    schema: mergeSchemas({
      schemas: [ schema ],
      resolvers
    }),
  });

1reaction

dncrewscommented, Sep 27, 2018

Expected Iterable, but did not find one for field Category.categories.

The error message is correct Your bug is here:

  const books = [
    {
      name: 'Harry Potter and the Chamber of Secrets',
      author: 'J.K. Rowling',
      categoryHierarchy: [
        { name: 'Fiction', categories: { name: 'Fantasy', categories: [] } }
      ]
    },
    {
      name: 'Jurassic Park',
      author: 'Michael Crichton',
      categoryHierarchy: [
        { name: 'Fiction', categories: { name: 'Sci-Fi', categories: [] } }
      ]
    },
  ];

You aren’t returning an Iterable (array) for the first level of categories. Should be:

  const books = [
    {
      name: 'Harry Potter and the Chamber of Secrets',
      author: 'J.K. Rowling',
      categoryHierarchy: [
        { name: 'Fiction', categories: [ { name: 'Fantasy', categories: [] } ] }
      ]
    },
    {
      name: 'Jurassic Park',
      author: 'Michael Crichton',
      categoryHierarchy: [
        { name: 'Fiction', categories: [ { name: 'Sci-Fi', categories: [] } ] }
      ]
    },
  ];

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