Add AdapterRegistryGenerator and related functionality for default adapter registration

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

@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2018 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi.kotlin.codegen.api
+
+import com.squareup.kotlinpoet.ClassName
+import com.squareup.kotlinpoet.CodeBlock
+import com.squareup.kotlinpoet.FileSpec
+import com.squareup.kotlinpoet.FunSpec
+import com.squareup.kotlinpoet.KModifier
+import com.squareup.kotlinpoet.ParameterizedTypeName.Companion.parameterizedBy
+import com.squareup.kotlinpoet.PropertySpec
+import com.squareup.kotlinpoet.STAR
+import com.squareup.kotlinpoet.TypeSpec
+import com.squareup.kotlinpoet.WildcardTypeName
+import com.squareup.kotlinpoet.asClassName
+
+private const val DEFAULT_ADAPTER_REGISTRY_PACKAGE_NAME_PREFIX = "com.squareup.moshi.generated"
+private const val DEFAULT_ADAPTER_REGISTRY_CLASS_NAME = "DefaultMoshiAdapterRegistry"
+
+public data class AdapterRegistration(
+  val targetClassName: ClassName,
+  val adapterClassName: ClassName,
+  val hasTypeParameters: Boolean
+)
+
+/** Generates a registry of adapters. */
+@InternalMoshiCodegenApi
+public class AdapterRegistryGenerator(
+  private val adapterRegistrations: List<AdapterRegistration>
+) {
+
+  public fun generate(): FileSpec {
+    // Get the top-level package name of the project (inferred from the shortest package name)
+    val packageName = run {
+      val firstPackage = adapterRegistrations
+        .filter { it.targetClassName.packageName.isNotEmpty() }
+        .minByOrNull { it.targetClassName.packageName.length }
+        ?.targetClassName?.packageName
+
+      firstPackage
+    } ?: "default" // fallback package name
+
+    // Generate a package hash of the package name to avoid potential collisions.
+    val packageHash = packageName.hashCode().toUInt().toString(16).take(12)
+    val registryPackageName = "$DEFAULT_ADAPTER_REGISTRY_PACKAGE_NAME_PREFIX.r$packageHash"
+
+    val moshiClass = ClassName("com.squareup.moshi", "Moshi")
+    val adapterRegistryClass = moshiClass.nestedClass("AdapterRegistry")
+    val jsonAdapterClass = ClassName("com.squareup.moshi", "JsonAdapter")
+    val typeClass = ClassName("java.lang.reflect", "Type")
+
+    val adaptersMapBuilder = CodeBlock.builder()
+    adaptersMapBuilder.add("mapOf(")
+
+    val nonGenericAdapters = adapterRegistrations.filter { !it.hasTypeParameters }
+    nonGenericAdapters.forEachIndexed { index, registration ->
+      if (index > 0) adaptersMapBuilder.add(",")
+      adaptersMapBuilder.add(
+        "\n  %T::class.java to %T::class.java",
+        registration.targetClassName,
+        registration.adapterClassName
+      )
+    }
+
+    if (nonGenericAdapters.isNotEmpty()) {
+      adaptersMapBuilder.add("\n")
+    }
+    adaptersMapBuilder.add(")")
+
+    val adaptersProperty = PropertySpec.builder(
+      "adapters",
+      Map::class.asClassName().parameterizedBy(
+        typeClass,
+        Class::class.asClassName().parameterizedBy(
+          WildcardTypeName.producerOf(jsonAdapterClass.parameterizedBy(STAR))
+        )
+      )
+    )
+      .addModifiers(KModifier.OVERRIDE)
+      .getter(
+        FunSpec.getterBuilder()
+          .addCode("return %L", adaptersMapBuilder.build())
+          .build()
+      )
+      .build()
+
+    val registryClass = TypeSpec.classBuilder(DEFAULT_ADAPTER_REGISTRY_CLASS_NAME)
+      .addSuperinterface(adapterRegistryClass)
+      .addProperty(adaptersProperty)
+      .build()
+
+    val file = FileSpec.builder(registryPackageName, DEFAULT_ADAPTER_REGISTRY_CLASS_NAME)
+      .addFileComment(
+        """
+            This file is auto generated by Moshi Kotlin CodeGen.
+            **DO NOT EDIT THIS FILE MANUALLY**
+          """.trimIndent()
+      )
+      .addType(registryClass)
+      .build()
+
+    return file
+  }
+}

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

@@ -37,6 +37,27 @@ public object Options {
    */
   public const val OPTION_GENERATE_PROGUARD_RULES: String = "moshi.generateProguardRules"
 
+  /**
+   * This boolean processing option can enable omission of `-keepnames` rules for target classes.
+   * Moshi's reflective lookup of adapters by class name will fail if obfuscation is applied
+   * to the target class. Only enable this if you are sure you won't be using Moshi's
+   * reflective adapter lookup.
+   * If you set [OPTION_GENERATE_DEFAULT_ADAPTER_REGISTRY] to `true` and decide to
+   * manually set the generated registry, you can also enable this option to
+   * avoid keeping target class names. (LET THEM BE OBFUSCATION, I DON'T WANT THE CLASS NAME TO BE RETAINED!)
+   * This option is automatically invalid if [OPTION_GENERATE_PROGUARD_RULES] is set to `false`.
+   * This is disabled by default for backward compatibility.
+   */
+  public const val OPTION_PROGUARD_RULES_DONT_KEEP_CLASS_NAMES: String = "moshi.proguardRulesDontKeepClassNames"
+
+  /**
+   * This boolean processing option can enable generation of a default adapter registry that
+   * a compile-time adapter registry that doesn't depend on class names for lookup.
+   * The generated registry content is a class annotated with `@JsonClass(generateAdapter = true)`.
+   * This is disabled by default for backward compatibility.
+   */
+  public const val OPTION_GENERATE_DEFAULT_ADAPTER_REGISTRY: String = "moshi.generateDefaultAdapterRegistry"
+
   /**
    * This boolean processing option controls whether or not Moshi will directly instantiate
    * JsonQualifier annotations in Kotlin 1.6+. Note that this is enabled by default in Kotlin 1.6

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

@@ -45,7 +45,7 @@ public data class ProguardConfig(
     return "META-INF/proguard/moshi-$canonicalName"
   }
 
-  public fun writeTo(out: Appendable): Unit = out.run {
+  public fun writeTo(out: Appendable, dontKeepClassNames: Boolean): Unit = out.run {
     //
     // -keepnames class {the target class}
     // -if class {the target class}
@@ -56,11 +56,17 @@ public data class ProguardConfig(
     //
     val targetName = targetClass.reflectionName()
     val adapterCanonicalName = ClassName(targetClass.packageName, adapterName).canonicalName
-    // Keep the class name for Moshi's reflective lookup based on it
-    appendLine("-keepnames class $targetName")
+
+    // Keep the class name for Moshi's reflective lookup based on it,
+    // but only if the user hasn't opted out of this.
+    if (!dontKeepClassNames)
+      appendLine("-keepnames class $targetName")
+
+    // Keep the `JsonClass` annotation on the target class, R8 will shrink it away otherwise.
+    appendLine("-keep${if (dontKeepClassNames) ",allowobfuscation" else ""} @com.squareup.moshi.JsonClass class *")
 
     appendLine("-if class $targetName")
-    appendLine("-keep class $adapterCanonicalName {")
+    appendLine("-${if (dontKeepClassNames) "keepclassmembers" else "keep"} class $adapterCanonicalName {")
     // Keep the constructor for Moshi's reflective lookup
     val constructorArgs = adapterConstructorParams.joinToString(",")
     appendLine("    public <init>($constructorArgs);")

moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/ksp/JsonClassSymbolProcessorProvider.kt

@@ -24,16 +24,22 @@ import com.google.devtools.ksp.processing.SymbolProcessor
 import com.google.devtools.ksp.processing.SymbolProcessorEnvironment
 import com.google.devtools.ksp.processing.SymbolProcessorProvider
 import com.google.devtools.ksp.symbol.KSAnnotated
+import com.google.devtools.ksp.symbol.KSClassDeclaration
 import com.google.devtools.ksp.symbol.KSDeclaration
 import com.google.devtools.ksp.symbol.KSFile
 import com.squareup.kotlinpoet.AnnotationSpec
 import com.squareup.kotlinpoet.ClassName
 import com.squareup.kotlinpoet.ksp.addOriginatingKSFile
+import com.squareup.kotlinpoet.ksp.toClassName
 import com.squareup.kotlinpoet.ksp.writeTo
 import com.squareup.moshi.JsonClass
 import com.squareup.moshi.kotlin.codegen.api.AdapterGenerator
+import com.squareup.moshi.kotlin.codegen.api.AdapterRegistration
+import com.squareup.moshi.kotlin.codegen.api.AdapterRegistryGenerator
 import com.squareup.moshi.kotlin.codegen.api.Options.OPTION_GENERATED
+import com.squareup.moshi.kotlin.codegen.api.Options.OPTION_GENERATE_DEFAULT_ADAPTER_REGISTRY
 import com.squareup.moshi.kotlin.codegen.api.Options.OPTION_GENERATE_PROGUARD_RULES
+import com.squareup.moshi.kotlin.codegen.api.Options.OPTION_PROGUARD_RULES_DONT_KEEP_CLASS_NAMES
 import com.squareup.moshi.kotlin.codegen.api.Options.POSSIBLE_GENERATED_NAMES
 import com.squareup.moshi.kotlin.codegen.api.ProguardConfig
 import com.squareup.moshi.kotlin.codegen.api.PropertyGenerator
@@ -63,6 +69,10 @@ private class JsonClassSymbolProcessor(
     }
   }
   private val generateProguardRules = environment.options[OPTION_GENERATE_PROGUARD_RULES]?.toBooleanStrictOrNull() ?: true
+  private val proguardRulesDontKeepClassNames = environment.options[OPTION_PROGUARD_RULES_DONT_KEEP_CLASS_NAMES]?.toBooleanStrictOrNull() ?: false
+  private val generateDefaultAdapterRegistry = environment.options[OPTION_GENERATE_DEFAULT_ADAPTER_REGISTRY]?.toBooleanStrictOrNull() ?: false
+
+  private val adapterRegistrations = mutableListOf<AdapterRegistration>()
 
   override fun process(resolver: Resolver): List<KSAnnotated> {
     val generatedAnnotation = generatedOption?.let {
@@ -100,13 +110,40 @@ private class JsonClassSymbolProcessor(
               .build()
           }
         preparedAdapter.spec.writeTo(codeGenerator, aggregating = false)
-        preparedAdapter.proguardConfig?.writeTo(codeGenerator, originatingFile)
+        preparedAdapter.proguardConfig?.writeTo(codeGenerator, originatingFile, proguardRulesDontKeepClassNames)
+
+        // Collect adapter registration information.
+        if (generateDefaultAdapterRegistry && type is KSClassDeclaration) {
+          val targetClassName = type.toClassName()
+          val adapterClassName = ClassName(
+            targetClassName.packageName,
+            "${targetClassName.simpleNames.joinToString("_")}JsonAdapter"
+          )
+          val hasTypeParameters = type.typeParameters.isNotEmpty()
+
+          adapterRegistrations.add(
+            AdapterRegistration(
+              targetClassName = targetClassName,
+              adapterClassName = adapterClassName,
+              hasTypeParameters = hasTypeParameters
+            )
+          )
+        }
       } catch (e: Exception) {
         logger.error(
           "Error preparing ${type.simpleName.asString()}: ${e.stackTrace.joinToString("\n")}",
         )
       }
     }
+
+    if (adapterRegistrations.isNotEmpty()) {
+      // FileAlreadyExistsException can happen if multiple compilations.
+      runCatching {
+        val adapterRegistryGenerator = adapterRegistryGenerator()
+        adapterRegistryGenerator.generate().writeTo(codeGenerator, aggregating = false)
+      }
+    }
+
     return emptyList()
   }
 
@@ -144,10 +181,12 @@ private class JsonClassSymbolProcessor(
 
     return AdapterGenerator(type, sortedProperties)
   }
+
+  private fun adapterRegistryGenerator() = AdapterRegistryGenerator(adapterRegistrations)
 }
 
 /** Writes this config to a [codeGenerator]. */
-private fun ProguardConfig.writeTo(codeGenerator: CodeGenerator, originatingKSFile: KSFile) {
+private fun ProguardConfig.writeTo(codeGenerator: CodeGenerator, originatingKSFile: KSFile, dontKeepClassNames: Boolean) {
   val file = codeGenerator.createNewFile(
     dependencies = Dependencies(aggregating = false, originatingKSFile),
     packageName = "",
@@ -156,5 +195,5 @@ private fun ProguardConfig.writeTo(codeGenerator: CodeGenerator, originatingKSFi
   )
   // Don't use writeTo(file) because that tries to handle directories under the hood
   OutputStreamWriter(file, StandardCharsets.UTF_8)
-    .use(::writeTo)
+    .use { writeTo(it, dontKeepClassNames) }
 }

moshi/src/main/java/com/squareup/moshi/Moshi.kt

@@ -45,6 +45,8 @@ public class Moshi internal constructor(builder: Builder) {
   private val lookupChainThreadLocal = ThreadLocal<LookupChain>()
   private val adapterCache = LinkedHashMap<Any?, JsonAdapter<*>?>()
 
+  internal val registry = builder.registry
+
   /** Returns a JSON adapter for `type`, creating it if necessary. */
   @CheckReturnValue
   public fun <T> adapter(type: Type): JsonAdapter<T> = adapter(type, NO_ANNOTATIONS)
@@ -191,6 +193,7 @@ public class Moshi internal constructor(builder: Builder) {
   public class Builder {
     internal val factories = mutableListOf<JsonAdapter.Factory>()
     internal var lastOffset = 0
+    internal var registry: AdapterRegistry? = null
 
     @CheckReturnValue
     @ExperimentalStdlibApi
@@ -239,10 +242,42 @@ public class Moshi internal constructor(builder: Builder) {
       addLast(AdapterMethodsFactory(adapter))
     }
 
+    public fun setRegistry(adapterRegistry: AdapterRegistry): Builder = apply {
+      this.registry = adapterRegistry
+    }
+
     @CheckReturnValue
     public fun build(): Moshi = Moshi(this)
   }
 
+  /**
+   * A registry of [JsonAdapter]s to be registered with a [Moshi] instance.
+   *
+   * To use, create a subclass and implement [adapters]. Then set an instance of your subclass on
+   * [Moshi.Builder.setRegistry].
+   *
+   * Example:
+   * ```
+   * class MyAdapterRegistry : Moshi.AdapterRegistry {
+   *   override val adapters = mapOf(
+   *     MyType::class.java to MyTypeJsonAdapter::class.java,
+   *     Types.newParameterizedType(List::class.java, String::class.java) to MyStringListJsonAdapter::class.java
+   *   )
+   * }
+   *
+   * val myRegistry = MyAdapterRegistry()
+   *
+   * val builder = Moshi.Builder().setRegistry(myRegistry)
+   * val moshi = builder.build()
+   * ```
+   */
+  public interface AdapterRegistry {
+    /**
+     * A map of [Type] to [JsonAdapter] to be registered.
+     */
+    public val adapters: Map<Type, Class<out JsonAdapter<*>>>
+  }
+
   /**
    * A possibly-reentrant chain of lookups for JSON adapters.
    *

moshi/src/main/java/com/squareup/moshi/internal/Util.kt

@@ -378,12 +378,24 @@ public fun Moshi.generatedAdapter(
   if (jsonClass == null || !jsonClass.generateAdapter) {
     return null
   }
-  val adapterClassName = Types.generatedJsonAdapterName(rawType.name)
+
+  val adapters = registry?.adapters
+
+  val rawAdapterClassName = Types.generatedJsonAdapterName(rawType.name)
   var possiblyFoundAdapter: Class<out JsonAdapter<*>>? = null
+
   return try {
     @Suppress("UNCHECKED_CAST")
-    val adapterClass = Class.forName(adapterClassName, true, rawType.classLoader) as Class<out JsonAdapter<*>>
+    val adapterClass = adapters?.firstNotNullOfOrNull { (regType, regAdapter) ->
+      if (typesMatch(rawType, regType)) {
+        regAdapter
+      } else {
+        null
+      }
+    } ?: Class.forName(rawAdapterClassName, true, rawType.classLoader) as? Class<out JsonAdapter<*>>?
+    ?: throw ClassNotFoundException()
     possiblyFoundAdapter = adapterClass
+
     var constructor: Constructor<out JsonAdapter<*>>
     var args: Array<Any>
     if (type is ParameterizedType) {