Resolve getDisplayName also when inherited or returning non-null String

[zaburen]

Fixes #135

What

• getDisplayNameFunction(): look the function up via memberFunctions instead of declaredMemberFunctions, so implementations inherited from an interface default or an abstract superclass are found. kotlin-reflect returns the most-derived override and the function is called on the provider instance, so dispatch stays correct.
• Accept a non-null String return type as well as String? (legal covariant overrides of AndroidX's getDisplayName(index: Int): String?).

Tests

• 3 new fixture providers beside the existing AndroidStringProviderWithDisplayName: declared non-null return, interface-default inherited, abstract-superclass inherited — each with its own preview group.
• New AndroidComposablePreviewParameterDisplayNameTest: scans the fixture package and asserts previewIndexDisplayName for all four shapes. Written before the fix: the three new cases failed with expected:<[Jim, Jens]> but was:<[null, null]>; the control (declared nullable) passed — and it keeps guarding the same-name decoy overload (getDisplayName(index: Int?) returning "WRONG").
• New goldens for the 3 new fixture previews (roborazzi runtime + sourceset, paparazzi) — the filenames now carry the Jim/Jens display names.
• All checks green locally on JDK 17: :tests:testApi (468 tests), :tests:testSourceSets, paparazziPreviewsRuntime/SourceSet -Pverify=true, roborazziPreviewsRuntime/SourceSet -Pverify=true, metalavaCheckCompatibility for all 5 modules (no public API change). No existing golden changes.

Behavior note

• Providers that inherit or covariantly narrow getDisplayName start resolving names — consumers who relied on the index fallback for such providers will see index → name screenshot-ID changes when they upgrade.
• AndroidX's base PreviewParameterProvider.getDisplayName (default null) now matches for every provider; it returns null, so previews without a real implementation keep today's index fallback unchanged.

Repro

https://github.com/zaburen/composable-preview-scanner-displayname-repro — fails 3/4 against 0.9.0; its -Pfixed mode swaps in the patched scanner from this branch and passes 4/4.

Summary by CodeRabbit

• Bug Fixes

  • Improved how preview parameter display names are detected, so the app now uses the correct non-null display-name method in more cases.
  • Better handling for display names inherited from interfaces and abstract superclasses, reducing incorrect preview name resolution.

• Tests

  • Added coverage for display-name edge cases to verify preview names are generated consistently across multiple provider setups.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 40734d59-62ad-4942-9aba-824fac385b6f

📥 Commits

Reviewing files that changed from the base of the PR and between 10b2f90 and ad930e3.

📒 Files selected for processing (2)

• tests/src/main/java/sergio/sastre/composable/preview/scanner/android/previewparametersdisplayname/Composables.kt
• tests/src/test/java/sergio/sastre/composable/preview/scanner/tests/api/main/screenshotid/AndroidComposablePreviewParameterDisplayNameEdgeCasesTest.kt

🚧 Files skipped from review as they are similar to previous changes (1)

• tests/src/main/java/sergio/sastre/composable/preview/scanner/android/previewparametersdisplayname/Composables.kt

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Walkthrough

The getDisplayName resolution in ComposablePreviewWithPreviewParameterMapper now uses memberFunctions instead of declaredMemberFunctions and accepts non-nullable String return types, fixing cases where inherited or non-nullable getDisplayName implementations previously resolved to null display names. New test fixtures and a parameterized JUnit test validate these scenarios.

Changes

getDisplayName resolution fix

Layer / File(s)	Summary
Mapper reflection lookup changes core/.../ComposablePreviewWithPreviewParameterMapper.kt	Switches from declaredMemberFunctions to memberFunctions for discovering getDisplayName, and widens the return-type match to accept non-nullable String in addition to String?.
New provider fixtures and previews tests/.../previewparametersdisplayname/Composables.kt	Updates the decoy getDisplayName(Int?) to throw instead of returning a wrong value; adds providers with non-nullable, interface-inherited, and superclass-inherited getDisplayName implementations, each wired to a new @Preview composable.
Display-name resolution tests tests/.../AndroidComposablePreviewParameterDisplayNameEdgeCasesTest.kt	Adds a parameterized test class with an enum of edge-case scenarios, scanning previews by group and asserting resolved display names match expectations.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Mapper as ComposablePreviewWithPreviewParameterMapper
  participant Reflection as KotlinReflect
  participant Provider as ProviderInstance
  Mapper->>Reflection: providerInstance::class.memberFunctions
  Reflection-->>Mapper: getDisplayName(Int) candidates (String or String?)
  Mapper->>Provider: call getDisplayName(index)
  Provider-->>Mapper: display name value (inherited or non-nullable)

Loading

Poem

A rabbit dug through reflection's burrow deep,
Found names that inherited providers keep.
No longer null, no longer lost,
Non-nullable strings cross the frost.
Hop, hop, hooray — the display names leap! 🐰✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the key fix: resolving getDisplayName for inherited implementations and non-null String returns.
Linked Issues check	✅ Passed	The code and tests address the issue’s required fixes: inherited lookup, non-null String support, and rejecting the Int? decoy overload.
Out of Scope Changes check	✅ Passed	The changes are focused on the reported display-name resolution bug and the accompanying validation tests.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[sergio-sastre]

@zaburen Looks very good!
I've just converted the tests into Parameterized, but everything remains.
Thank you very much for your contribution, I'll merge it and release a new version with the bug fix today

[zaburen]

@sergio-sastre
Thank you very much for your attention and time on this issue.

My team and I greatly appreciate you and your amazing tool!