How to add a UsagePlan to an imported Rest API

[owenashurst]

Hi,

I'm having an issue where I have a core infrastructure stack, let's call this Stack A, that has an API Gateway with a CloudFront CDN. This stack exports the RestApiId and RootResourceId. I'm then importing this into my other stack, let's call this Stack B, that's solely for a lambda function. The method creation works great in stack B. However, when I come to add a usage plan for an API Key to secure the function, it throws an error because it can't serialise the deployment stage.

Here's the code:

var apiGateway = RestApi.FromRestApiAttributes(this, "api-gateway", new RestApiAttributes
            {
                RestApiId = Fn.ImportValue("APIGatewayId"),
                RootResourceId = Fn.ImportValue("APIGatewayRootResourceId")
            });

......

var apiKey = new ApiKey(this, "api-key", new ApiKeyProps
            {
                ApiKeyName = "Admin UI",
                DefaultIntegration = lambdaIntegration
            });

            var deployment = new Deployment(this, "deployment", new DeploymentProps
            {
                Api = apiGateway
            });

            var usagePlan = new UsagePlan(this, "usage-plan", new UsagePlanProps
            {
                Name = "Admin UI",
                ApiStages = new UsagePlanPerApiStage[]
                {
                    new UsagePlanPerApiStage
                    {
                        Api = apiGateway,
                        Stage = apiGateway.DeploymentStage
                    }
                }
            });

            usagePlan.AddApiKey(apiKey);

Exception:

Unhandled exception. System.Exception: Of property aws-cdk-lib.aws_apigateway.RestApiBase.deploymentStage: Unable to serialize value as aws-cdk-lib.aws_apigateway.Stage
├── 🛑 Failing value is undefined
╰── 🔍 Failure reason(s):
    ╰─ A value is required (type is non-optional)
   at Amazon.JSII.Runtime.Services.Client.TryDeserialize[TResponse](String responseJson)
   at Amazon.JSII.Runtime.Services.Client.ReceiveResponse[TResponse]()
   at Amazon.JSII.Runtime.Services.Client.Send[TRequest,TResponse](TRequest requestObject)
   at Amazon.JSII.Runtime.Services.Client.Get(GetRequest request)
   at Amazon.JSII.Runtime.Services.Client.Get(ObjectReference objectReference, String property)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.<>c__DisplayClass9_0`1.<GetInstanceProperty>b__0(IClient client)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.GetPropertyCore[T](JsiiPropertyAttribute propertyAttribute, Func`2 getFunc)
   at Amazon.JSII.Runtime.Deputy.DeputyBase.GetInstanceProperty[T](String propertyName)
   at Amazon.CDK.AWS.APIGateway.RestApiBase.get_DeploymentStage()

Has anyone any ideas how I can get around this?

Thanks,
Owen