Error Handling

#Custom Not Found Handler

By default, Zuplo will return a 404 (using problem details) if no matching path/method combination is found. You can override this behavior by adding code to the zuplo.runtime.ts file (see runtime extensions).

For example - a custom not found handler can be used to return a 405 - Method Not Allowed if a matching path is found, but no matching METHOD, here is an example function that would implement this behavior:

export function runtimeInit(runtime: RuntimeExtensions) {
  //add a custom not found handler
  runtime.notFoundHandler = async (request, context, notFoundOptions) => {
    if (notFoundOptions.routesMatchedByPathOnly.length > 0) {
      // It is required to have an 'Allow' header with a 405 response
      // Generate a string of allowed methods
      const allowedMethods = notFoundOptions.routesMatchedByPathOnly
        .map((route) => route.methods)
        .reduce((acc, val) => acc.concat(val), [])
        .join(", ");

      return HttpProblems.methodNotAllowed(
        request,
        context,
        {},
        { allow: allowedMethods },
      );
    }

    return HttpProblems.notFound(request, context);
  };
}

An error in your zuplo.runtime.ts can break your gateway for all requests. Be sure to carefully review any custom code in this file and add generous error handling where appropriate.

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