Property Injectors usage for custom L2/L3

[msessa]

Hi @pcheungamz

I've been following the development of property injectors and can see the potential to simplify adoption of CDK in our organization.

I'm just wondering, will this mechanism be available to custom L2/L3 constructs built by the users?

for example will I be able to define a MyCustomConstruct class with MyCustomConstructProps interface which allows an injector to override the properties?

Currently it doesn't seem like the propertyInjectable decorator is available for use outside the main cdk code repo.

[pcheungamz]

Hi @msessa ,

Property Injectors were designed for all CDK L2 non-abstract Constructs. But I think it should work for you MyCustomConstruct too.

MyCustomConstruct must have these 2 things:

1. Have class decorator @propertyInjectable
2. Have public static readonly PROPERTY_INJECTION_ID: string = 'your.unique.path.to.MyCustomConstruct';

propertyInjectable is defined here: https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/core/lib/prop-injectable.ts#L20

I don't understand why it would not work for MyCustomConstruct. What kind of error are you getting?

[msessa]

@pcheungamz

To use it in my own construct library I would need to import the decorator first. eg:

import { propertyInjectable } from 'aws-cdk-lib';

However that doesn't compile because

'"aws-cdk-lib"' has no exported member named 'propertyInjectable'. Did you mean 'IPropertyInjector'?

I suspect that's because the prop-injectable.ts file is not exported here:
https://github.com/aws/aws-cdk/blob/main/packages/aws-cdk-lib/core/lib/index.ts

[pcheungamz]

I see. You are correct. I think the aws-cdk team made that refactoring intentionally.

[msessa]

@rix0rrr

Do you see any issues in exporting the decorator for use on downstream, higher level constructs and/or end-user applications?