Update metro to v0.10.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
dev.zacsweers.metro	0.9.4 → 0.10.0
dev.zacsweers.metro:dev.zacsweers.metro.gradle.plugin	0.9.4 → 0.10.0
dev.zacsweers.metro:metrox-android	0.9.4 → 0.10.0

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Release Notes

ZacSweers/metro (dev.zacsweers.metro)

v0.10.0

Compare Source

2026-01-19

Behavior Changes

• Enable contributesAsInject by default. See its docs for more details, but in short this means that @Inject is now optional on @ContributesBinding, @ContributesIntoSet, and @ContributesIntoMap annotated declarations.

  @​ContributesBinding(AppScope::class)
  // @&#8203;Inject // <-- now implicit!
  class TacoImpl(...) : Taco

• [Gradle / FIR] Enable FIR hint generation by default on Kotlin 2.3.20-Beta1 or later.
  • By extension, this resolves Metro's most subscribed issue (#​460) by enabling cross-module contribution/aggregation features in non-jvm/android compilations 🎉.
  • Note that there is a separate known kotlinc issue around qualifier annotations that affects native builds and is targeted for 2.3.20-Beta2. Follow #​1556 for updates.
• [Gradle / FIR] Enable top-level function injection by default on Kotlin 2.3.20-Beta1 or later.
• [Gradle / FIR] Disable automatic transformation of providers to private + deprecate the option, as this results in less efficient code generation and somewhat unclear error messages. It's recommended to write a lint check in another static analysis tool if you want this, for example this implementation from slack-lints.
  • Metro may add an option for the inverse in the future. i.e., allow writing a private provider in source but then transform it to internal at compile-time.

New

• Support Map<K, Lazy<V>> and Map<K, Provider<Lazy<V>> multibindings expressions.
• [FIR/IR] Report diagnostics for unmatched exclusions and replacements during contribution merging. These are written to reportsDestination if enabled, and should be used for debugging only.
• [IR / Gradle] Add new experimental enableSwitchingProviders option. If enabled, this changes code generation to use "switching providers" to defer classloading until a giving binding is actually requested.
  • This is analogous to Dagger's fastInit feature.
  • You should really only use this if you've benchmarked it and measured a meaningful difference, as it comes with the same tradeoffs (always holding a graph instance ref, etc.)
• [IR / Gradle] Add an unusedGraphInputsSeverity option to report diagnostics for unused direct graph inputs. This includes any @Provides or @Includes parameters to graph factories or managed binding containers declared via the @DependencyGraph.includes annotation.
  • This is in addition to the existing reportsDestination-only diagnostic for unused bindings, but limited to bindings that we know are not reused elsewhere and can thus safely soft-enforce at compile-time.
  • This matches a similar feature in Dagger.

Enhancements

• [IR] Restructure graph validation and generation to be separate phases, allowing for whole-graph validation before any code gen runs and better optimizing shared bindings across graph extension hierarchies.
• [IR] Improve member injection error trace in graph validation.
  • Previously it would show something like this

    dev.zacsweers.metro.MembersInjector<test.FeatureScreen> is requested at
        [test.FeatureGraph] test.FeatureGraph#inject()
    

  • Now it will specify the injected type is being injected instead

    test.Dependency is requested at
        [test.FeatureGraph] test.FeatureScreen.dependency
    test.FeatureScreen is injected at
        [test.FeatureGraph] test.FeatureGraph#inject()
    

  • It now also reports the location at the exact member injection callable declaration, rather than the graph.
• [IR] Validate parameter type keys on native builds to help clarify encounters with KT-83427. Example below:

  e: Mirror/create function parameter type mismatch:
    - Source:         com.example.navigation.NavigationProviders.navigationSerializationModule
    - Mirror param:   @&#8203;com.example.app.navigation.NavigationSerializers kotlin.collections.Set<kotlinx.serialization.modules.SerializersModule>
    - create() param: kotlin.collections.Set<kotlinx.serialization.modules.SerializersModule>
  
  This is a known bug in the Kotlin compiler, follow https://github.com/ZacSweers/metro/issues/1556
  

• [IR] Avoid generating unnecessary Provider refcounts for bindings only used by graph injector functions.
• [IR] When reporting graph failures in dynamic graphs, report the original call location in error reporting.
• [IR] Optimize equals/hashCode in type keys. Benchmarks show a ~2% macro improvement.
• [IR/Sharding] Rebalance shard groups after computing shard bindings.
• [Gradle] Generalize support for sourcing default values from gradle/system properties + document.

Fixes

• [FIR] Ensure hint functions generated by FIR hint generation match the visibility of the source contributor.
• [FIR/IR] Always check for @Inject-annotated constructor even if class is annotated. This is important for the contributesAsInject feature, as it would previously always use the primary constructor in these cases.
• [FIR/IR] Don't clear reports dir between FIR and IR compiler phases.
• [IR] Never eagerly init graph extension impls (scoped or not).
• [IR] Don't cache creator-less scoped graph extension impls in their parent graphs. This was initially implemented this way due to a misunderstanding to how Dagger generated subcomponents! Getters for graph extensions now always return new instances.
• [IR] Check for open or final modality on classes first before searching for injectable constructors.
• [IR] Mark all supertypes' member injections as dependencies of subtypes' member injections. That's a wordier way of saying that member-injecting a class Dog that extends Animal also depends on member-injected dependencies of Animal.
• [IR] Don't process companion objects of graphs or binding containers independently of their parent classes.
• [IR/Native] Work around Abstract function '___' is not implemented in non-abstract class 'Impl' info warnings from native compilations.
• [IR/Dynamic Graphs] Always check if a key is replaced by a dynamic type key when building binding graphs. Previously, some bindings would be added even if a dynamic key was available, resulting in unexpected DuplicateBinding errors.
• [IC] Record lookups of contributed classes when looking up hints from IR. Previously Metro only recorded a lookup of the generated hint function, which appears to not be enough for Kotlin 2.3.20.
• [IC] Link IR-generated hint function files back to source class via expect-actual tracker to link their compilations. This fixes an edge case where simply changing a contribution scope (or removing it) could leave behind a stale hint file that downstream compilations would incidentally read.

Misc Changes

• [IR] Already mentioned above, but worth calling out again — creator-less scoped graph extensions are no longer cached in their parent graphs. Accessors to this will always get new instances now.
• [IR] Report log files reported from within graph generation now use snake-cased fully-qualified names of the impl graph as the file name suffix.
• [IR] Do not report similar bindings when a missing binding has type kotlin.Any. In practice this reported all available bindings.
• [interop-dagger] Update to Dagger 2.58.
• [Docs] Publish kdocs for guice/jakarta/javax interop and metrox artifacts to doc site.
• [Docs] Expand IDE support docs.
• [Docs] Update adoption.md docs about subcomponents interop.
• Test Kotlin 2.3.10-RC.
• Test Kotlin 2.3.20-Beta1.

Contributors

Special thanks to the following contributors for contributing to this release!

• @​neworld
• @​JoelWilcox
• @​C2H6O

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