Check for same subtypes before erroring on duplicate labels (#602)

Resolves #507

CHANGELOG.md

@@ -6,6 +6,7 @@ Changelog
 
 - Improve moshi-sealed KSP error messages.
 - Fix fallback adapter support in IR code gen not recognizing Moshi parameters to primary constructors.
+- Check for same subtypes before erroring on duplicate labels in moshi-sealed IR.
 
 0.27.0
 ------

moshi-ir/moshi-compiler-plugin/src/main/kotlin/dev/zacsweers/moshix/ir/compiler/sealed/SealedAdapterGenerator.kt

@@ -317,8 +317,10 @@ private constructor(
         }
 
     seenLabels.put(mainLabel, subtype)?.let { prev ->
-      logger.error(target) {
-        "Duplicate label '$mainLabel' defined for ${subtype.fqNameWhenAvailable} and ${prev.fqNameWhenAvailable}."
+      if (prev != subtype) {
+        logger.error(target) {
+          "Duplicate label '$mainLabel' defined for ${subtype.fqNameWhenAvailable} and ${prev.fqNameWhenAvailable}."
+        }
       }
       return null
     }

moshi-ir/moshi-compiler-plugin/src/test/kotlin/dev/zacsweers/moshix/ir/compiler/MoshiIrVisitorTest.kt

@@ -1076,6 +1076,36 @@ class MoshiIrVisitorTest(private val useK2: Boolean) {
     assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
   }
 
+  // Covers cases where a nested sealed interface is also implemented by a subtype that implements
+  // the super type
+  @Test
+  fun nestedSealedWithCommonSubtypes() {
+    val source =
+      kotlin(
+        "BaseType.kt",
+        """
+      package test
+      import com.squareup.moshi.JsonClass
+      import dev.zacsweers.moshix.sealed.annotations.TypeLabel
+      import dev.zacsweers.moshix.sealed.annotations.NestedSealed
+
+      @JsonClass(generateAdapter = true, generator = "sealed:type")
+      sealed interface Foo {
+
+        @NestedSealed
+        sealed interface SuperFoo : Foo
+
+        @JsonClass(generateAdapter = true)
+        @TypeLabel("real")
+        data class RealFoo(val value: String) : SuperFoo, Foo
+      }
+    """,
+      )
+
+    val result = compile(source)
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
+  }
+
   private fun prepareCompilation(
     generatedAnnotation: String? = null,
     vararg sourceFiles: SourceFile,

moshi-sealed/codegen/src/main/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorProvider.kt

@@ -418,8 +418,10 @@ private class MoshiSealedSymbolProcessor(environment: SymbolProcessorEnvironment
         }
 
     seenLabels.put(mainLabel, className)?.let { prev ->
-      logger.error("Duplicate label '$mainLabel' defined for $className and $prev.", rootType)
-      return null
+      if (prev != className) {
+        logger.error("Duplicate label '$mainLabel' defined for $className and $prev.", rootType)
+        return null
+      }
     }
 
     labels += mainLabel

moshi-sealed/codegen/src/test/kotlin/dev/zacsweers/moshix/sealed/codegen/ksp/MoshiSealedSymbolProcessorTest.kt

@@ -517,6 +517,36 @@ class MoshiSealedSymbolProcessorProviderTest(private val useKSP2: Boolean) {
       )
   }
 
+  // Covers cases where a nested sealed interface is also implemented by a subtype that implements
+  // the super type
+  @Test
+  fun nestedSealedWithCommonSubtypes() {
+    val source =
+      kotlin(
+        "BaseType.kt",
+        """
+      package test
+      import com.squareup.moshi.JsonClass
+      import dev.zacsweers.moshix.sealed.annotations.TypeLabel
+      import dev.zacsweers.moshix.sealed.annotations.NestedSealed
+
+      @JsonClass(generateAdapter = true, generator = "sealed:type")
+      sealed interface Foo {
+
+        @NestedSealed
+        sealed interface SuperFoo : Foo
+
+        @JsonClass(generateAdapter = true)
+        @TypeLabel("real")
+        data class RealFoo(val value: String) : SuperFoo, Foo
+      }
+    """,
+      )
+
+    val result = compile(source)
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
+  }
+
   private fun prepareCompilation(vararg sourceFiles: SourceFile): KotlinCompilation =
     KotlinCompilation().apply {
       sources = sourceFiles.toList()