EvaluateMappingTemplate

Source: src/AWS/AppSync/EvaluateMappingTemplate.ts

Runtime binding for appsync:EvaluateMappingTemplate — evaluate a VTL request/response mapping template against a mock context without touching a deployed resolver. The VTL twin of EvaluateCode, for resolvers defined with requestMappingTemplate/responseMappingTemplate instead of APPSYNC_JS code.

An account-level operation: the binding takes no resource. Template evaluation errors do not fail the effect — they surface on the response’s error field. Provide AppSync.EvaluateMappingTemplateHttp on the hosting function’s Effect to implement the binding.

Evaluating Mapping Templates

// init — account-level binding takes no resource
const evaluateTemplate = yield* AppSync.EvaluateMappingTemplate();

// runtime
const result = yield* evaluateTemplate({
  template: `{ "sum": $util.toJson($ctx.args.a + $ctx.args.b) }`,
  context: JSON.stringify({ arguments: { a: 2, b: 3 } }),
});
// JSON.parse(result.evaluationResult!) → { sum: 5 }