[kikoso]

Summary

maps-compose has no check on its public API today. AGENTS.md says public API changes must be additive and backward compatible, but nothing enforces it, so an accidental break (a removed overload, a changed parameter type, a default that moved) would only be found by users after a release. android-maps-utils already guards this with the binary compatibility validator; this PR sets up the same thing here.

• org.jetbrains.kotlinx.binary-compatibility-validator 0.18.2, same version as android-maps-utils.
• PublishingConventionPlugin registers apiBuild, apiDump and apiCheck for each library module, reading the release classes.jar, exactly like android-maps-utils does (the plugin's own Android integration does not fit AGP 9 built-in Kotlin). check depends on apiCheck, and there are root apiDump/apiCheck tasks for all modules.
• The current public API is committed in maps-compose/api/maps-compose.api (319 lines), maps-compose-utils/api/maps-compose-utils.api (51) and maps-compose-widgets/api/maps-compose-widgets.api (6). The generated R classes and their nested classes are ignored, since they are public in bytecode but not part of the API.
• CI runs apiCheck in the test workflow.
• AGENTS.md explains when to run apiDump.

A few points worth to mention

• The .api files are also a nice snapshot of what we expose today. It is worth a quick look: some things are public only for technical reasons (i.e. ComposableSingletons$GoogleMapKt, generated by the Compose compiler).
• The check compares binary signatures. Renaming a parameter keeps the signature, so it passes, but it still breaks callers using named arguments. AGENTS.md mentions it so we keep an eye on it in review.

Testing

• ./gradlew apiDump generates the three files, and ./gradlew apiCheck passes on them.
• Adding a required parameter to ScaleBar makes :maps-compose-widgets:apiCheck fail with the old and new signatures; reverting it passes again.
• ./gradlew build apiCheck (same as the updated CI command) and spotlessKotlinCheck pass locally.

[github-actions]

Coverage (unit tests)

Compared against 174f0fd on main (#1060).

Module	Line %	Change	Branch %	Change
maps-compose	15.28%	no change	3.76%	no change
maps-compose-utils	6.09%	no change	4.47%	no change
maps-compose-widgets	10.88%	no change	11.11%	no change
TOTAL	12.99%	no change	4.12%	no change

_{Line and branch coverage from unit test reports. History is recorded on the coverage-history branch after each merge to main.}

[googlemaps-bot]

Coverage (instrumentation tests)

Overall Project	43.69%	🍏

There is no coverage information present for the Files changed