Fix support for classes w/ multiple constructors in code gen (#976)

* Fix broken test

This test suite doesn't run on CI builds but fails locally since the method was moved

* Add multiple constructors test case

* Implement TypeName.asTypeBlock()

* Make DEFAULT_CONSTRUCTOR_MARKER public

* Look up constructor via getDeclaredConstructor with exact param types

Resolves #975

* Remove dead code

kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/AdapterGenerator.kt

@@ -20,6 +20,7 @@ import com.squareup.kotlinpoet.AnnotationSpec
 import com.squareup.kotlinpoet.CodeBlock
 import com.squareup.kotlinpoet.FileSpec
 import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.INT
 import com.squareup.kotlinpoet.KModifier
 import com.squareup.kotlinpoet.MemberName
 import com.squareup.kotlinpoet.NameAllocator
@@ -31,6 +32,7 @@ import com.squareup.kotlinpoet.TypeSpec
 import com.squareup.kotlinpoet.TypeVariableName
 import com.squareup.kotlinpoet.asClassName
 import com.squareup.kotlinpoet.asTypeName
+import com.squareup.kotlinpoet.joinToCode
 import com.squareup.moshi.JsonAdapter
 import com.squareup.moshi.JsonReader
 import com.squareup.moshi.JsonWriter
@@ -48,6 +50,14 @@ internal class AdapterGenerator(
     target: TargetType,
     private val propertyList: List<PropertyGenerator>
 ) {
+
+  companion object {
+    private val DEFAULT_CONSTRUCTOR_EXTRA_PARAMS = arrayOf(
+        CodeBlock.of("%T::class.javaPrimitiveType", INT),
+        CodeBlock.of("%T.DEFAULT_CONSTRUCTOR_MARKER", Util::class)
+    )
+  }
+
   private val nonTransientProperties = propertyList.filterNot { it.isTransient }
   private val className = target.typeName.rawType()
   private val visibility = target.visibility
@@ -56,6 +66,7 @@ internal class AdapterGenerator(
   private val nameAllocator = NameAllocator()
   private val adapterName = "${className.simpleNames.joinToString(separator = "_")}JsonAdapter"
   private val originalTypeName = target.typeName
+  private val originalRawTypeName = originalTypeName.rawType()
 
   private val moshiParam = ParameterSpec.builder(
       nameAllocator.newName("moshi"),
@@ -158,7 +169,7 @@ internal class AdapterGenerator(
   }
 
   private fun generateToStringFun(): FunSpec {
-    val name = originalTypeName.rawType().simpleNames.joinToString(".")
+    val name = originalRawTypeName.simpleNames.joinToString(".")
     val size = TO_STRING_SIZE_BASE + name.length
     return FunSpec.builder("toString")
         .addModifiers(KModifier.OVERRIDE)
@@ -201,10 +212,12 @@ internal class AdapterGenerator(
     // JsonReader.Options.
     var propertyIndex = 0
     var maskIndex = 0
+    val constructorPropertyTypes = mutableListOf<CodeBlock>()
     for (property in propertyList) {
       if (property.isTransient) {
         if (property.hasConstructorParameter) {
           maskIndex++
+          constructorPropertyTypes += property.target.type.asTypeBlock()
         }
         continue
       }
@@ -238,6 +251,9 @@ internal class AdapterGenerator(
               exception)
         }
       }
+      if (property.hasConstructorParameter) {
+        constructorPropertyTypes += property.target.type.asTypeBlock()
+      }
       propertyIndex++
       maskIndex++
     }
@@ -267,12 +283,13 @@ internal class AdapterGenerator(
     if (useDefaultsConstructor) {
       classBuilder.addProperty(constructorProperty)
       // Dynamic default constructor call
-      val rawOriginalTypeName = originalTypeName.rawType()
       val nonNullConstructorType = constructorProperty.type.copy(nullable = false)
+      val args = constructorPropertyTypes.plus(DEFAULT_CONSTRUCTOR_EXTRA_PARAMS)
+          .joinToCode(", ")
       val coreLookupBlock = CodeBlock.of(
-          "%T.lookupDefaultsConstructor(%T::class.java)",
-          MOSHI_UTIL,
-          rawOriginalTypeName
+          "%T::class.java.getDeclaredConstructor(%L)",
+          originalRawTypeName,
+          args
       )
       val lookupBlock = if (originalTypeName is ParameterizedTypeName) {
         CodeBlock.of("(%L·as·%T)", coreLookupBlock, nonNullConstructorType)
@@ -280,7 +297,7 @@ internal class AdapterGenerator(
         coreLookupBlock
       }
       val initializerBlock = CodeBlock.of(
-          "this.%1N ?:·%2L.also·{ this.%1N·= it }",
+          "this.%1N·?: %2L.also·{ this.%1N·= it }",
           constructorProperty,
           lookupBlock
       )
@@ -310,7 +327,7 @@ internal class AdapterGenerator(
           // We have to use the default primitive for the available type in order for
           // invokeDefaultConstructor to properly invoke it. Just using "null" isn't safe because
           // the transient type may be a primitive type.
-          result.addCode(property.target.type.defaultPrimitiveValue())
+          result.addCode(property.target.type.rawType().defaultPrimitiveValue())
         } else {
           result.addCode("%N", property.localName)
         }

kotlin/codegen/src/main/java/com/squareup/moshi/kotlin/codegen/api/kotlintypes.kt

@@ -15,6 +15,8 @@
  */
 package com.squareup.moshi.kotlin.codegen.api
 
+import com.squareup.kotlinpoet.ANY
+import com.squareup.kotlinpoet.ARRAY
 import com.squareup.kotlinpoet.BOOLEAN
 import com.squareup.kotlinpoet.BYTE
 import com.squareup.kotlinpoet.CHAR
@@ -25,9 +27,11 @@ import com.squareup.kotlinpoet.FLOAT
 import com.squareup.kotlinpoet.INT
 import com.squareup.kotlinpoet.KModifier
 import com.squareup.kotlinpoet.LONG
+import com.squareup.kotlinpoet.NOTHING
 import com.squareup.kotlinpoet.ParameterizedTypeName
 import com.squareup.kotlinpoet.SHORT
 import com.squareup.kotlinpoet.TypeName
+import com.squareup.kotlinpoet.TypeVariableName
 import com.squareup.kotlinpoet.UNIT
 import com.squareup.kotlinpoet.asTypeName
 
@@ -49,10 +53,41 @@ internal fun TypeName.defaultPrimitiveValue(): CodeBlock =
       FLOAT -> CodeBlock.of("0f")
       LONG -> CodeBlock.of("0L")
       DOUBLE -> CodeBlock.of("0.0")
-      UNIT, Void::class.asTypeName() -> throw IllegalStateException("Parameter with void or Unit type is illegal")
+      UNIT, Void::class.asTypeName(), NOTHING -> throw IllegalStateException("Parameter with void, Unit, or Nothing type is illegal")
       else -> CodeBlock.of("null")
     }
 
+internal fun TypeName.asTypeBlock(): CodeBlock {
+  when (this) {
+    is ParameterizedTypeName -> {
+      return if (rawType == ARRAY) {
+        CodeBlock.of("%T::class.java", copy(nullable = false))
+      } else {
+        rawType.asTypeBlock()
+      }
+    }
+    is TypeVariableName -> {
+      val bound = bounds.firstOrNull() ?: ANY
+      return bound.asTypeBlock()
+    }
+    is ClassName -> {
+      return when (this) {
+        BOOLEAN, CHAR, BYTE, SHORT, INT, FLOAT, LONG, DOUBLE -> {
+          if (isNullable) {
+            // Remove nullable but keep the java object type
+            CodeBlock.of("%T::class.javaObjectType", copy(nullable = false))
+          } else {
+            CodeBlock.of("%T::class.javaPrimitiveType", this)
+          }
+        }
+        UNIT, Void::class.asTypeName(), NOTHING -> throw IllegalStateException("Parameter with void, Unit, or Nothing type is illegal")
+        else -> CodeBlock.of("%T::class.java", copy(nullable = false))
+      }
+    }
+    else -> throw UnsupportedOperationException("Parameter with type '${javaClass.simpleName}' is illegal. Only classes, parameterized types, or type variables are allowed.")
+  }
+}
+
 internal fun KModifier.checkIsVisibility() {
   require(ordinal <= ordinal) {
     "Visibility must be one of ${(0..ordinal).joinToString { KModifier.values()[it].name }}. Is $name"

kotlin/reflect/src/main/test/java/com/squareup/moshi/kotlin/reflect/KotlinJsonAdapterTest.kt

@@ -15,7 +15,7 @@ class KotlinJsonAdapterTest {
     val moshi = Moshi.Builder()
         .add(KotlinJsonAdapterFactory())
         .build()
-    val adapter = moshi.adapter<Data>()
+    val adapter = moshi.adapter(Data::class.java)
     assertThat(adapter.toString()).isEqualTo(
         "KotlinJsonAdapter(com.squareup.moshi.kotlin.reflect.KotlinJsonAdapterTest.Data).nullSafe()"
     )

kotlin/tests/src/test/kotlin/com/squareup/moshi/kotlin/DualKotlinTest.kt

@@ -322,6 +322,26 @@ class DualKotlinTest(useReflection: Boolean) {
 
   @JsonClass(generateAdapter = true)
   class InternalAbstractProperty(override val test: String) : InternalAbstractPropertyBase()
+
+  // Regression test for https://github.com/square/moshi/issues/975
+  @Test fun multipleConstructors() {
+    val adapter = moshi.adapter<MultipleConstructorsB>()
+
+    assertThat(adapter.toJson(MultipleConstructorsB(6))).isEqualTo("""{"f":{"f":6},"b":6}""")
+
+    @Language("JSON")
+    val testJson = """{"b":6}"""
+    val result = adapter.fromJson(testJson)!!
+    assertThat(result.b).isEqualTo(6)
+  }
+
+  @JsonClass(generateAdapter = true)
+  class MultipleConstructorsA(val f: Int)
+
+  @JsonClass(generateAdapter = true)
+  class MultipleConstructorsB(val f: MultipleConstructorsA = MultipleConstructorsA(5), val b: Int) {
+    constructor(f: Int, b: Int = 6): this(MultipleConstructorsA(f), b)
+  }
 }
 
 // Has to be outside since inline classes are only allowed on top level