Invoking synth multiple times with adapter throws errors

[sapslaj]

Description

Attempting to invoke synth multiple times causes the adapter to attempt to re-convert existing resources. For most practical cases there's no reason to run synth multiple times, with the major exception being tests. It's not too uncommon to see Testing.synth(stack) multiple times in a test in my experience, so having synth be essentially non-idempotent was a nasty surprise for me.

CDKTF AWS Adapter Version

v0.13.5

AWS CDK Version

v2.128.0

Gist

https://gist.github.com/sapslaj/017ed9ec3265d062e8207df408a0564c

Possible Solutions

The most brute-force approach would be to simply mark any resources that have already been converted during convert() and just ignore them, but that's not super great if you synth, mutate a construct, then run synth again.

Perhaps a better approach would be to remove any existing resource that matches the logical ID and then define a new one. Somewhere right here:

cdktf-aws-cdk/src/aws-adapter.ts

Line 157 in c0ac04d

const res = m.resource(scope, logicalId, props);

// pseudo-code, untested

// remove any child that matches the logical ID so we can overwrite it
scope.tryRemoveChild(logicalId);

// create new resource
const res = m.resource(scope, logicalId, props);

Workarounds

I messed around with trying to unregister the Aspect that the adapter uses after it finishes, but that's egregiously fragile and has other downsides.

The best workaround is... to just not synth twice!

// ...

const synthed = Testing.synth(stack);
expect(synthed).toBeValidTerraform();
expect(synthed).toHaveResourceWithProperties(...);

Anything Else?

Yes, this is very much an edge case, but it was quite surprising and took a good hour of debugging before I realized what was happening 😅.

References

No response

Help Wanted

• I'm interested in contributing a fix myself

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[github-actions]

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