From 3db6d16dca991abbbbed5e7441606966c4d44810 Mon Sep 17 00:00:00 2001
From: Ralf Wondratschek <rwo@amazon.com>
Date: Mon, 28 Oct 2024 13:00:54 -0700
Subject: [PATCH] Generate binding method for subcomponent factory

Generate a binding method for types annotated with `@ContributesSubcomponent.Factory` in the parent scope. This allows us to inject the factory type itself.

Fixes #49
---
 ...ContributesSubcomponentFactoryProcessor.kt | 17 +++++++-
 .../ContributesSubcomponentProcessorTest.kt   | 41 +++++++++++++++++++
 2 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/compiler/src/main/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentFactoryProcessor.kt b/compiler/src/main/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentFactoryProcessor.kt
index 4b1ba7a..5242e00 100644
--- a/compiler/src/main/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentFactoryProcessor.kt
+++ b/compiler/src/main/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentFactoryProcessor.kt
@@ -10,10 +10,12 @@ import com.google.devtools.ksp.symbol.KSAnnotated
 import com.google.devtools.ksp.symbol.KSClassDeclaration
 import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.FileSpec
+import com.squareup.kotlinpoet.FunSpec
 import com.squareup.kotlinpoet.TypeSpec
 import com.squareup.kotlinpoet.ksp.addOriginatingKSFile
 import com.squareup.kotlinpoet.ksp.toClassName
 import com.squareup.kotlinpoet.ksp.writeTo
+import me.tatarka.inject.annotations.Provides
 import software.amazon.lastmile.kotlin.inject.anvil.ContextAware
 import software.amazon.lastmile.kotlin.inject.anvil.ContributesSubcomponent
 import software.amazon.lastmile.kotlin.inject.anvil.ContributesTo
@@ -27,7 +29,8 @@ import software.amazon.lastmile.kotlin.inject.anvil.internal.Subcomponent
  * In the lookup package [LOOKUP_PACKAGE] a new interface is generated extending the contributed
  * interface. To avoid name clashes the package name of the original interface is encoded in the
  * interface name. This is very similar to [ContributesTo] with the key differences that there
- * are more strict checks and that [Subcomponent] is added as marker.
+ * are more strict checks and that [Subcomponent] is added as marker. Further, an `@Provides`
+ * (binding) function is generated to be able to inject the factory type.
  * ```
  * package software.amazon.test
  *
@@ -46,7 +49,10 @@ import software.amazon.lastmile.kotlin.inject.anvil.internal.Subcomponent
  *
  * @Origin(Subcomponent.Factory::class)
  * @Subcomponent
- * interface SoftwareAmazonTestSubcomponentFactory : Subcomponent.Factory
+ * interface SoftwareAmazonTestSubcomponentFactory : Subcomponent.Factory {
+ *     @Provides
+ *     fun provideSubcomponentFactory(): Subcomponent.Factory = this
+ * }
  * ```
  */
 @OptIn(KspExperimental::class)
@@ -95,6 +101,13 @@ internal class ContributesSubcomponentFactoryProcessor(
                     .addOriginAnnotation(factory)
                     .addAnnotation(Subcomponent::class)
                     .addSuperinterface(factory.toClassName())
+                    .addFunction(
+                        FunSpec.builder("provide${factory.innerClassNames()}")
+                            .addAnnotation(Provides::class)
+                            .returns(factory.toClassName())
+                            .addStatement("return this")
+                            .build()
+                    )
                     .build(),
             )
             .build()
diff --git a/compiler/src/test/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentProcessorTest.kt b/compiler/src/test/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentProcessorTest.kt
index f351ccf..3a1e415 100644
--- a/compiler/src/test/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentProcessorTest.kt
+++ b/compiler/src/test/kotlin/software/amazon/lastmile/kotlin/inject/anvil/processor/ContributesSubcomponentProcessorTest.kt
@@ -490,6 +490,47 @@ class ContributesSubcomponentProcessorTest {
         }
     }
 
+    @Test
+    fun `the factory interface is provided and can be injected in the parent scope`() {
+        compile(
+            """
+            package software.amazon.test
+    
+            import software.amazon.lastmile.kotlin.inject.anvil.AppScope
+            import software.amazon.lastmile.kotlin.inject.anvil.ContributesSubcomponent
+            import software.amazon.lastmile.kotlin.inject.anvil.ContributesTo
+            import software.amazon.lastmile.kotlin.inject.anvil.MergeComponent
+            import software.amazon.lastmile.kotlin.inject.anvil.SingleIn
+            import me.tatarka.inject.annotations.Component
+            import me.tatarka.inject.annotations.Provides
+
+            @MergeComponent(AppScope::class)
+            @Component
+            @SingleIn(AppScope::class)
+            interface ComponentInterface : ComponentInterfaceMerged {
+                val factory: LoggedInComponent.Factory
+            }
+
+            @ContributesSubcomponent(LoggedInScope::class)
+            @SingleIn(LoggedInScope::class)
+            interface LoggedInComponent {
+                @ContributesSubcomponent.Factory(AppScope::class)
+                interface Factory {
+                    fun loggedInComponent(): LoggedInComponent 
+                }
+            }
+            """,
+            scopesSource,
+        ) {
+            val component = componentInterface.newComponent<Any>()
+            val loggedInComponent = component::class.java.methods
+                .single { it.name == "getFactory" }
+                .invoke(component)
+
+            assertThat(loggedInComponent).isNotNull()
+        }
+    }
+
     private val JvmCompilationResult.componentInterface2: Class<*>
         get() = classLoader.loadClass("software.amazon.test.ComponentInterface2")