[eduardomourar]

Related issue

Fixes #416

Description

Test for an undefined default instead of truthiness, so false, 0 and an empty string render a lookup() call. Update the fqn tests to use lookupNested and the edge integration expectations.

Checklist

• I have updated the PR title to match CDKTN's style guide
• I have run the linter on my code locally
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation if applicable
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works if applicable
• New and existing unit tests pass locally with my changes

[jsteinich]

Thanks for picking this up! I checked the fix on Terraform 1.14.3 and OpenTofu 1.12.6, in both JSON and HCL synth. false, 0 and "" now render lookup() and return the default for a missing key. Keys that exist evaluate the same as before, and the JSII signature is unchanged.

One gap: null. It now passes the !== undefined guard, but _lookup's variadic listOf() drops null elements (functions/helpers.ts:76). So Fn.lookup(m, "k", null) renders lookup(m, "k"), which still errors on a missing key. Terraform and OpenTofu both accept lookup(m, "k", null) and return null. Could you pass an explicit null token and add a null case to the test.each?

if (defaultValue !== undefined)
  return Fn._lookup(inputMap, key, [
    defaultValue === null ? Token.nullValue() : defaultValue,
  ]);

A nit: the inline snapshot in iterator.test.ts was re-indented by one space. Restoring the old indent keeps the diff to the boolean_map line.

For the release notes (no action needed here): a falsy default whose type differs from the map's element type (e.g. "" on a map(number)), or a list passed as inputMap, used to work by accident through the property-access path. These now fail at plan, as the same calls already do with a truthy default.

HCL synth has the same truthiness pattern for variable attributes and locals. That's out of scope here, so it's tracked separately in #589.

[eduardomourar]

All addressed now.