GraphQL links not working

[SabbeRubbish]

Hi guys/girls,

Writing my first gatsby source plugin #superexcited.
All is working fine, I'm getting my data from external service and created nodes in GraphQL:

"allSalonizedAppointments": {
      "nodes": [
        {
          "customer_id": "7508867",
          "id": "27201514",
          "customer": null
        }
      ]
    },
    "allSalonizedCustomers": {
      "nodes": [
        {
          "first_name": "John",
          "last_name": "Doe",
          "id": "7508867"
        },
        {
          "first_name": "Jane",
          "last_name": "Doe",
          "id": "7522368"
        }
      ]
    }
  },

As you can see I've already added a "customer" field, trying to populate it with salonizedCustomer type. GraphQL already finds all fields, but the link is giving me issues:

exports.createSchemaCustomization = ({ actions, schema }) => {
  const { createTypes } = actions;
  createTypes(`
    type salonizedAppointments implements Node {
      customer_id: String!
      customer: salonizedCustomers @link(from: "salonizedCustomers.id" by: "customer_id")
    }
    type salonizedCustomers implements Node {
      id: String!
    }
  `);
};

I've already tried using other syntax using the more explicit syntax, but to no avail.
I'm guessing some issues may be related to the fact that the actual data has salonizedAppointments.id as a String and salonizedCustomers.id as an int, but as I've treated both of them in the schema as Strings I don't see the issue.

Some help would be really appreciated!

[vladar]

Try something like this instead:

exports.createSchemaCustomization = ({ actions, schema }) => {
  const { createTypes } = actions;
  createTypes(`
    type salonizedAppointments implements Node {
      customer_id: String!
      customer: salonizedCustomers @link(from: "customer_id")
    }
    type salonizedCustomers implements Node {
      id: String!
    }
  `);
};

[SabbeRubbish]

Hi vlad,

Thanks again, but making them all strings didn't help either.
I've made minimal reproduction in which I also don't succeed in making the foreign key relationship:
https://github.com/SabbeRubbish/bug-repro

[vladar]

I think you are using the wrong argument (by vs from). I've changed this line in your repro and it worked:

exports.createSchemaCustomization = ({ actions, schema }) => {
    const { createTypes } = actions;
    createTypes(`
      type salonizedAppointments implements Node {
        customer_id: String!
-        customer: salonizedCustomers @link(by: "customer_id")
+        customer: salonizedCustomers @link(from: "customer_id")
      }
      type salonizedCustomers implements Node {
        id: String!
      }
    `);
  };

[SabbeRubbish]

wow vlad, you found it!
Not entirely my mistake though, as this documentation article is stating it incorrectly:

type MarkdownRemark implements Node {
  frontmatter: Frontmatter
}
type Frontmatter {
  author: AuthorJson @link # default foreign-key relation by `id`
  reviewers: [AuthorJson] @link(by: "email") # foreign-key relation by custom field
}
type AuthorJson implements Node {
  posts: [MarkdownRemark] @link(by: "frontmatter.author.email", from: "email") # easy back-ref
}

Line 6 has the incorrect "by" mentioned that I took over in my example. I'll make a PR to correct that #30174.

But your suggestion to convert all ints to **string*s was also important. Both pieces fixed my puzzle!
Thanks!

[vladar]

I think documentation is correct 😅 but I do agree that argument naming is confusing.

The argument from defines a field on this type to use for matching. The argument by defines a field on the referenced type to use for matching.

So take this example:

type Frontmatter {
  reviewers: [AuthorJson] @link(by: "email") # foreign-key relation by custom field
}

It implies that your markdown looks like this:

---
reviewers:
  - [email protected]
  - [email protected]
---

And your author JSON looks like this:

[
  {
    "name": "Doe",
    "firstName": "Jane",
    "email": "[email protected]",
    "joinedAt": "2018-01-01"
  },
  {
    "name": "Doe",
    "firstName": "Zoe",
    "email": "[email protected]",
    "receivedSwag": true
  }
]

Then you read @link directive this way:

Use the value from the field `Frontmatter.reviewers` and match it by the field `AuthorJSON.email`

(from is omitted so we use the field value itself as a source for matching).

[SabbeRubbish]

Ok that makes sense now :)
Sorry for the bogus PR, I'll retract it (somehow :)).