Rule Ideas

[WhosNickDoglio]

Vanilla Dagger

• Components must be abstract
• Favor Constructor injection over member injection
• Avoid unnecessary Provides methods and just constructor injection
• Favor Binds over Provides
• Methods annotated with @Binds must be abstract
• @Provides method should be static
• If a Factory or Builder is present in a Component make sure it's called.
• If a class has @Provides or @Binds methods make sure it's annotated with @Module.
• valid provision methods
• val member injection methods
• @Binds return type is super type of impl
• Suggest using KSP over KAPT

Anvil

• Use @MergeX or ContributesTo annotations on Component and Subcomponents
• Use @ContributesTo annotations on each Module
• Favor @ContributesBinding over @Binds
• @ContributesBinding has a super class
• Cant be used in Java
• Warn not compatible with KSP Dagger yet

Hilt

• Use @InstallIn annotations on each Module
• Use @InstallBinding over @Binds (Add InstallBinding google/dagger#3516)
• Don't forget hilt annotations (@HiltAndroidApp, @AndroidEntryPoint, @HiltViewModel)
• use by hiltViewModel() for getting viewModels from DI Graph
• @EntryPoint can only be applied to interfaces
• Missing @InstallIn
• Suggest using KSP over KAPT

Inspiration / Resources

• Keeping your Daggers sharp (Square)
• That Missing Guide: How to use Dagger2
• Dagger 2 on Android: The Simple Way
  • It's complicated, but it doesn't have to be: a Dagger journey
  • Dagger 2 on Android: The Official Guidelines You Should Be Following
• Refactoring our Dependency Injection using Anvil
• Extending Anvil for Fun and Profit
• Dagger + Anvil: Learning to Love Dependency Injection on Android (Article)
• Dagger + Anvil: Learning to Love Dependency Injection on Android (Droidcon talk)
• N26 Path to Anvil
• Fragmented episode 202: Dagger on the Anvil with Ralf Wondratschek
• Dagger documentation
• Anvil GitHub project

[WhosNickDoglio]

Block Impl from being injected if it used @ContributesBinding

Logic might look like something like this:

• Check if class has an @Inject annotation
• if it does, check if the constructor parameters are abstract
• if a parameter is not abstract check if it has a super that's not Any or Object
• Complain if it does

This might have a large amount of false positives but we'll see 🤷

Maybe this is better as SPI check?

[WhosNickDoglio]

flag incorrect usage of @BindsInstance