Feature request: enable feature flags when running tests

[jfly]

Description

Right now, feature flags in cdk.json take effect when inside of a cdk synth, but are not picked up when in tests. @nija-at says that this is intentional.

Use Case

I don't think this is a very sane default for users of cdk: I can totally see why people working on cdk would not want feature flags to automagically get enabled in tests, but IMO that's not appropriate behavior for users of cdk. For example, we recently started getting warnings like this when running cdk synth:

[WARNING] @aws-cdk/aws-kms.KeyProps#trustAccountIdentities is deprecated.
redundant with the @aws-cdk/aws-kms:defaultKeyPolicies feature flag
This API will be removed in the next major release.

This felt pretty silly to us, because even though we had the @aws-cdk/aws-kms:defaultKeyPolicies enabled in our cdk.json file, we could not remove this trustAccountIdentities parameter without breaking tests.

Proposed Solution

I'd love to see cdk.json feature flags handled the same way between cdk synth and unittests.

Other information

No response

Acknowledge

• I may be able to implement this feature request
• This feature might incur a breaking change

[njlynch]

When invoking the cdk CLI, the CLI itself takes care of loading the cdk.json file and parsing out the context; however, it's difficult to provide a one-size-fits-all solution to enable that context while running inside any given test runner in all of the languages we support.

That being said, the solution in any given language + test runner is fairly trivial; you simply need to pass the context from cdk.json and pass it into your App creation. Here's an example for Typescript + Jest:

let app: cdk.App;
let context: { [key: string]: any };
beforeAll(async () => { context = JSON.parse((await fs.readFile('cdk.json', 'utf8'))).context; });
beforeEach(() => { app = new cdk.App({ context }); });

I hope that helps.

[github-actions]

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