Kotlin: fix type of nested class reached via imported outer type

[vlsi]

Why

On Kotlin sources, ShortenFullyQualifiedTypeReferences corrupts a nested type reached through an imported outer type. Given:

import org.apiguardian.api.API

@API(status = API.Status.EXPERIMENTAL, since = "5.6")
class Foo

it rewrites API.Status.EXPERIMENTAL to Status.EXPERIMENTAL without adding an import, so Status no longer resolves and the file fails to compile. The equivalent Java source is left untouched. This surfaced running CodeCleanup over Apache JMeter's mixed Java/Kotlin sources — #8237.

What

The root cause is in Kotlin type attribution, not the recipe. PsiElementAssociations.matchClassId0 matched a reference's source text only against the fully-qualified class name (org.apiguardian.api.API.Status). The import-shortened form API.Status never matched, so the lookup walked up the outerClassId chain and returned the outer class org.apiguardian.api.API. The nested reference therefore carried the outer type, whose owningClass is null — which is exactly the guard ShortenFullyQualifiedTypeReferences uses to decide a reference is top-level and safe to shorten.

matchClassId0 now resolves every way a nested type can be written to its own class id:

• fully qualified (foo.bar.A.B) and relative to an imported outer (A.B) match by text;
• an import alias (import ... API as GuardApi, then GuardApi.Status) matches by leaf name plus nesting depth, since the aliased root matches neither the fully-qualified nor the package-relative name;
• an imported nested type (import foo.bar.A.B, then B.A.C) matches a trailing run of the nested names.

The two multi-segment fallbacks require at least two segments, so a single receiver name whose leaf repeats deeper (the outer A of A.B.A.C) is not matched too deep.

• Broaden matchClassId0 to the alias and imported-nested forms.
• Add type-mapping tests next to the existing nestedFieldAccessType / nestedFieldAccessWithPackage cases: import-shortened at one and multiple levels, same simple name across different outers, and an imported nested class.
• Add recipe-level reproduction tests from ShortenFullyQualifiedTypeReferences drops the qualifier and import for nested types on Kotlin #8237 for the imported-outer and aliased-outer forms.
• Closes http://github.com/openrewrite/rewrite/issues/8237

How to verify

./gradlew :rewrite-kotlin:test — the full module passes, including the new ShortenFullyQualifiedTypeReferencesKotlinTest cases and the KotlinTypeMappingTest nestedFieldAccess* / nestedTypesWithSameSimpleNameFromDifferentOuters cases.

[vlsi]

I just saw the build produced 27635 lines. That is huge. Have you considered reducing the output? I see you have --info which sounds strange to me.
At this scale I do not think build log is helpful. How do you identify the reasons for the build failure?

[greg-at-moderne]

I suggest we rewrite the test cases to be generic, i.e. possibly use some standard library references or existing dependencies. This way we can refrain from adding this (test) dependency.