(aws-lambda-python): Change assetHashType to cdk.AssetHashType.SOURCE

[fsmanuel]

I noticed that my lambda layers get rebuild everytime I run the cdk.

Becaus the current implementation defines cdk.AssetHashType.BUNDLE it has some side effects if dependencies change. I can mitigate the side effects by specifining the versions in the requirements.txt e.g. pandas==1.1.* but still it always bundles the layer even if nothing changes.

I would propose to change the assetHashType to SOURCE especially because BUNDLE is deprecated and the suggested change to OUTPUT would still have the described side effects mentioned above.

aws-cdk/packages/@aws-cdk/aws-lambda-python/lib/bundling.ts

Line 65 in 7dc45b2

assetHashType: cdk.AssetHashType.BUNDLE,

That would also solve #12684

[TLadd]

Would the fix for this also address aws-lambda-nodejs? As seen in #11625 (comment), node js lambda functions always end up being rebuilt as well.

[fsmanuel]

@TLadd no, the current PR only addresses the python lambdas. But for nodejs the same approach would work:

aws-cdk/packages/@aws-cdk/aws-lambda-nodejs/lib/bundling.ts

Lines 37 to 42 in 7dc45b2

	public static bundle(options: BundlingProps): AssetCode {
	return Code.fromAsset(path.dirname(options.depsLockFilePath), {
	assetHashType: cdk.AssetHashType.OUTPUT,
	bundling: new Bundling(options),
	});
	}

Currently we are discussing the best solution to this in the PR #12984

[github-actions]

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