Improve directives support

[FluorescentHallucinogen]

Directives may alter execution and type validation behavior.

const a = buildSchema(/* GraphQL */ `
  directive @foo on FIELD

  type Dummy {
    field: String @foo
  }
`);

const b = buildSchema(/* GraphQL */ `
  directive @foo on FIELD

  type Dummy {
    field: String
  }
`);

const changes = diff(a, b);
...
expect(change.type).toEqual('FIELD_DIRECTIVE_REMOVED');

const changes = diff(b, a);
...
expect(change.type).toEqual('FIELD_DIRECTIVE_ADDED');

See possible directive locations: https://spec.graphql.org/draft/#sec-Type-System.Directives

Directive order is significant.

const a = buildSchema(/* GraphQL */ `
  directive @addExternalFields(source: String!) on FIELD
  directive @excludeField(source: String!) on FIELD

  type Person @addExternalFields(source: "profiles") @excludeField(name: "photo") {
    name: String
  }
`);

const b = buildSchema(/* GraphQL */ `
  directive @addExternalFields(source: String!) on FIELD
  directive @excludeField(source: String!) on FIELD

  type Person @excludeField(name: "photo") @addExternalFields(source: "profiles") {
    name: String
  }
`);

const changes = diff(a, b);
...
expect(change.type).toEqual('DIRECTIVE_ORDER_CHANGED');

[FluorescentHallucinogen]

@kamilkisiela PTAL.

[Voldemat]

Is there any plans to implement this feature? This feature would allow to statically define all validation rules on schema fields and ensure that they are in sync with server definitions, therefore providing end-to-end validation safety. I`m currently looking into this, so any help or suggestions will be appreciated.