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This is the documentation for the old GraphQL Mesh version v0. We recommend upgrading to the latest GraphQL Mesh version v1.

Migrate to GraphQL Mesh v1

Extend Transform (experimental)

extend transform allows you to extend the source’s schema directly on the source level. But this might cause inconsistency if the schema heavily relies on that schema’s existing structure. This transform can be used for the data sources that return fixed results.

For example, OpenAPI and JSON Schema handlers are good examples of this kind of source. In contrast, PostGraphile and GraphQL handlers don’t because they rely on their existing structure. The resolvers added by this transform access directly to root, args, and context of that schema, so you cannot use selectionSet (actually, you shouldn’t, because this is not a root level transform).

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Note: This transform cannot access other sources; it can only be used at the source level.

⚠️

Please DO NOT use this transform unless you know what you’re doing! We strongly recommend you to extend the schema using additionalTypeDefs and additionalResolvers as described in Extend Schema part in this documentation.

How to use?

Add the following configuration under the source configuration;

.meshrc.yaml

transforms:
  - extend:
      typeDefs: ./someTypeDefs.graphql
      resolvers: ./someResolvers.ts

You can extend the existing types in:

someTypeDefs.graphql

extend type User {
  fullName: String
}

And define resolvers for those types;

someResolvers.ts

module.exports = {
  User: {
    fullName: user => `${user.firstName} ${user.lastName}` // e.g. `user` is the raw result returned by your data source
  }
}

Config API Reference

typeDefs (type: Any)
resolvers (type: Any)

Federation Subgraph Prune