From 5d34a1f14a63a256dfc3fd4e290a1280931a6c40 Mon Sep 17 00:00:00 2001
From: Egor Andreevici <egor@squareup.com>
Date: Thu, 21 Apr 2022 17:25:18 -0400
Subject: [PATCH] Unwrap nested KSTypeAliases recursively

---
 .../com/squareup/kotlinpoet/ksp/ksTypes.kt    | 39 +++++++++++--------
 .../ksp/test/processor/TestProcessorTest.kt   |  4 ++
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/ksTypes.kt b/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/ksTypes.kt
index 96c6fad883..3de5a77361 100644
--- a/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/ksTypes.kt
+++ b/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/ksTypes.kt
@@ -70,25 +70,34 @@ internal fun KSType.toTypeName(
     }
     is KSTypeParameter -> typeParamResolver[decl.name.getShortName()]
     is KSTypeAlias -> {
-      val extraResolver = if (decl.typeParameters.isEmpty()) {
-        typeParamResolver
-      } else {
-        decl.typeParameters.toTypeParameterResolver(typeParamResolver)
-      }
+      var typeAlias: KSTypeAlias = decl
+      var arguments = arguments
 
-      val resolvedType = decl.type.resolve()
-      val mappedArgs = mapTypeArgumentsFromTypeAliasToAbbreviatedType(
-        typeParamResolver = typeParamResolver,
-        typeAlias = decl,
-        typeAliasTypeArguments = arguments,
-        abbreviatedType = resolvedType,
-      )
+      var resolvedType: KSType
+      var mappedArgs: List<KSTypeArgument>
+      var extraResolver: TypeParameterResolver
+      while (true) {
+        resolvedType = typeAlias.type.resolve()
+        mappedArgs = mapTypeArgumentsFromTypeAliasToAbbreviatedType(
+          typeAlias = typeAlias,
+          typeAliasTypeArguments = arguments,
+          abbreviatedType = resolvedType,
+        )
+        extraResolver = if (typeAlias.typeParameters.isEmpty()) {
+          typeParamResolver
+        } else {
+          typeAlias.typeParameters.toTypeParameterResolver(typeParamResolver)
+        }
+
+        typeAlias = resolvedType.declaration as? KSTypeAlias ?: break
+        arguments = mappedArgs
+      }
 
       val abbreviatedType = resolvedType
         .toTypeName(extraResolver)
         .copy(nullable = isMarkedNullable)
         .rawType()
-        .withTypeArguments(mappedArgs)
+        .withTypeArguments(mappedArgs.map { it.toTypeName(typeParamResolver) })
 
       val aliasArgs = typeArguments.map { it.toTypeName(typeParamResolver) }
 
@@ -104,11 +113,10 @@ internal fun KSType.toTypeName(
 
 @KotlinPoetKspPreview
 private fun mapTypeArgumentsFromTypeAliasToAbbreviatedType(
-  typeParamResolver: TypeParameterResolver,
   typeAlias: KSTypeAlias,
   typeAliasTypeArguments: List<KSTypeArgument>,
   abbreviatedType: KSType,
-): List<TypeName> {
+): List<KSTypeArgument> {
   return abbreviatedType.arguments
     .map { typeArgument ->
       // Check if type argument is a reference to a typealias type parameter, and not an actual type.
@@ -121,7 +129,6 @@ private fun mapTypeArgumentsFromTypeAliasToAbbreviatedType(
         typeArgument
       }
     }
-    .map { it.toTypeName(typeParamResolver) }
 }
 
 /**
diff --git a/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt b/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
index e22ae003d6..5cfb657eec 100644
--- a/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
+++ b/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
@@ -270,6 +270,8 @@ class TestProcessorTest {
            typealias GenericTypeAlias = List<String>
            typealias GenericMapTypeAlias<V, K> = Map<K, V>
            typealias T1Unused<T1, T2> = Map<T2, String>
+           typealias A1<T1, T2> = A2<T2, T1>
+           typealias A2<T2, T3> = Map<T3, T2>
 
            @ExampleAnnotation
            class Example {
@@ -278,6 +280,7 @@ class TestProcessorTest {
                genericAlias: GenericTypeAlias,
                genericMapAlias: GenericMapTypeAlias<String, Int>,
                t1Unused: T1Unused<String, Int>,
+               a1: A1<String, Int>,
              ) {
              }
            }
@@ -305,6 +308,7 @@ class TestProcessorTest {
           genericAlias: List<String>,
           genericMapAlias: Map<Int, String>,
           t1Unused: Map<Int, String>,
+          a1: Map<String, Int>,
         ): Unit {
         }
       }