ResolverResource

Source: src/AWS/AppSync/Resolver.ts

An AppSync resolver — attaches request/response logic to a schema field.

UNIT resolvers target a single data source; PIPELINE resolvers run a sequence of Functions. The modern default is APPSYNC_JS code (a module exporting request(ctx) / response(ctx)); VTL mapping templates remain supported.

Unit Resolvers

const resolver = yield* AppSync.Resolver("AddResolver", {
  api,
  typeName: "Query",
  fieldName: "add",
  dataSource: lambdaDS,
  code: `
    export function request(ctx) {
      return { operation: "Invoke", payload: { args: ctx.args } };
    }
    export function response(ctx) {
      return ctx.result;
    }
  `,
});

Pipeline Resolvers

const fn = yield* AppSync.Function("Step", {
  api,
  dataSource: lambdaDS,
  code: fnCode,
});
const resolver = yield* AppSync.Resolver("PipelineResolver", {
  api,
  typeName: "Query",
  fieldName: "double",
  kind: "PIPELINE",
  pipelineFunctionIds: [fn.functionId],
  code: `
    export function request(ctx) { return {}; }
    export function response(ctx) { return ctx.prev.result; }
  `,
});