GraphQL support

Engine

The GraphQL "Engine" defines the logic for expressing a service in terms of GraphQL. It is used to power the schema generator included in this package and can be used for building custom generators for emitting GraphQL-related code.

Generator

The provided generator creates a GraphQL schema. This package also provides a definition for the rel metadata type that defines the relationship between types. This allows the generator to produce a scehma that can be implemented solely by calls to the methods also defined in the service.

Use the rel metadata type and the provided rules to ensure that the service design includes the necessary features to support generating a GraphQL schema.

Rules

TODO

Relational Metadata

The rel metadata type provides the syntax for defining relationships between types.

primaryKey

Use primaryKey to indicate that a property is the primary key of an object. In a generated GraphQL schema, primary key fields are rendered with an ID! type.

Usage:

{ "primaryKey": true }

foreignKey

Add foreignKey to a property define a foreign key relationship to another type's primary key. The GraphQL schema will replace the field with a resolver to the other entity. If the field is not defined in the service, then the GraphQL schema will define an "external entity" to support federation.

Usage:

{
  "type": "user",
  "property": "id"
}

To create a connection resolver on the foreign type, use "many": true. This will generate the resolver and the appropriate connection and edge types.

{
  "type": "user",
  "property": "id",
  "many": true
}

A foreign key may also be added to a parameter to indicate that it refers to a type's primary key. (Note that many is has no effect in this context.) Add a foreign key to a method parameter is required to indicate that a method can be used to batch-load a particular type.

edge

Add edge to a type to define a many-to-many edge between to types. For example, to define a many-to-many edge between the product and order types, create a productOrder type with a foreign key to both products and orders. Then, add an edge rel object that includes both foreign key properties. Doing so will establish the many-to-many relationship.

Usage:

{ "edge": ["productId", "orderId"] }

This relationship will generate two connection types—one from products to orders and another going the other way. All properties of the productOrder edge type (except for the foreign keys) will be added to the GraphQL edge types.

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For contributors:

Run this project

1. Install packages: npm ci
2. Build the code: npm run build
3. Run it! npm start

Note that the lint script is run prior to build. Auto-fixable linting or formatting errors may be fixed by running npm run fix.

Create and run tests

1. Add tests by creating files with the .test.ts suffix
2. Run the tests: npm t
3. Test coverage can be viewed at /coverage/lcov-report/index.html

Publish a new package version

1. Ensure latest code is published on the main branch.
2. Create the new version number with npm version {major|minor|patch}
3. Push the branch and the version tag: git push origin main --follow-tags

The publish workflow will build and pack the new version then push the package to NPM. Note that publishing requires write access to the main branch.

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