Add support for readOnly/writeOnly adapters for codeGen (kapt/KSP).

.gitignore

@@ -28,3 +28,4 @@ obj
 
 # Temporary until generating a docsite
 docs/
+/local.properties

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 autoService = "1.1.1"
 jvmTarget = "1.8"
-kotlin = "1.9.21"
+kotlin = "1.9.23"
 kotlinCompileTesting = "0.4.0"
 kotlinpoet = "1.14.2"
 ksp = "1.9.23-1.0.19"

jitpack.yml

@@ -0,0 +1,6 @@
+jdk:
+  - openjdk20
+before_install:
+   - sdk install java 17.0.1-open
+   - sdk install java 20.0.2-open
+   - sdk use java 20.0.2-open

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

@@ -55,6 +55,8 @@ private const val TO_STRING_SIZE_BASE = TO_STRING_PREFIX.length + 1 // 1 is the
 public class AdapterGenerator(
   private val target: TargetType,
   private val propertyList: List<PropertyGenerator>,
+  private val readOnly: Boolean,
+  private val writeOnly: Boolean,
 ) {
 
   private companion object {
@@ -273,8 +275,9 @@ public class AdapterGenerator(
         return CodeBlock.of("%N[%L]", typesParam, index)
       }
     }
-
-    result.addProperty(optionsProperty)
+    if (!writeOnly) {
+      result.addProperty(optionsProperty)
+    }
     for (uniqueAdapter in nonTransientProperties.distinctBy { it.delegateKey }) {
       result.addProperty(
         uniqueAdapter.delegateKey.generateProperty(
@@ -287,8 +290,8 @@ public class AdapterGenerator(
     }
 
     result.addFunction(generateToStringFun())
-    result.addFunction(generateFromJsonFun(result))
-    result.addFunction(generateToJsonFun())
+    result.addFunction(generateFromJsonFun(result, writeOnly))
+    result.addFunction(generateToJsonFun(readOnly))
 
     return result.build()
   }
@@ -321,12 +324,27 @@ public class AdapterGenerator(
       .build()
   }
 
-  private fun generateFromJsonFun(classBuilder: TypeSpec.Builder): FunSpec {
+  private fun generateFromJsonFun(classBuilder: TypeSpec.Builder, writeOnly: Boolean): FunSpec {
     val result = FunSpec.builder("fromJson")
       .addModifiers(KModifier.OVERRIDE)
       .addParameter(readerParam)
       .returns(originalTypeName)
 
+    if (writeOnly) {
+      val name = originalRawTypeName.simpleNames.joinToString(".")
+      result.addStatement(
+        "throw·%T(%M(%L)·{ append(%S).append(%S).append('%L').append(%S) })",
+        UnsupportedOperationException::class,
+        MemberName("kotlin.text", "buildString"),
+        TO_STRING_SIZE_BASE + name.length + 53,
+        TO_STRING_PREFIX,
+        name,
+        ")",
+        " is write only. @JsonClass is set with writeOnly=true",
+      )
+      return result.build()
+    }
+
     for (property in nonTransientProperties) {
       result.addCode("%L", property.generateLocalProperty())
       if (property.hasLocalIsPresentName) {
@@ -677,12 +695,27 @@ public class AdapterGenerator(
     )
   }
 
-  private fun generateToJsonFun(): FunSpec {
+  private fun generateToJsonFun(readOnly: Boolean): FunSpec {
     val result = FunSpec.builder("toJson")
       .addModifiers(KModifier.OVERRIDE)
       .addParameter(writerParam)
       .addParameter(valueParam)
 
+    if (readOnly) {
+      val name = originalRawTypeName.simpleNames.joinToString(".")
+      result.addStatement(
+        "throw·%T(%M(%L)·{ append(%S).append(%S).append('%L').append(%S) })",
+        UnsupportedOperationException::class,
+        MemberName("kotlin.text", "buildString"),
+        TO_STRING_SIZE_BASE + name.length + 51,
+        TO_STRING_PREFIX,
+        name,
+        ")",
+        " is read only. @JsonClass is set with readOnly=true",
+      )
+      return result.build()
+    }
+
     result.beginControlFlow("if (%N == null)", valueParam)
     result.addStatement(
       "throw·%T(%S)",

moshi-kotlin-codegen/src/main/java/com/squareup/moshi/kotlin/codegen/apt/JsonClassCodegenProcessor.kt

@@ -104,7 +104,15 @@ public class JsonClassCodegenProcessor : AbstractProcessor() {
       }
       val jsonClass = type.getAnnotation(annotation)
       if (jsonClass.generateAdapter && jsonClass.generator.isEmpty()) {
-        val generator = adapterGenerator(type, cachedClassInspector) ?: continue
+        if (jsonClass.readOnly && jsonClass.writeOnly) {
+          messager.printMessage(
+            Diagnostic.Kind.ERROR,
+            "@JsonClass can't be both readOnly and writeOnly",
+            type,
+          )
+          continue
+        }
+        val generator = adapterGenerator(type, cachedClassInspector, jsonClass.readOnly, jsonClass.writeOnly) ?: continue
         val preparedAdapter = generator
           .prepare(generateProguardRules) { spec ->
             spec.toBuilder()
@@ -137,6 +145,8 @@ public class JsonClassCodegenProcessor : AbstractProcessor() {
   private fun adapterGenerator(
     element: TypeElement,
     cachedClassInspector: MoshiCachedClassInspector,
+    readOnly: Boolean,
+    writeOnly: Boolean,
   ): AdapterGenerator? {
     val type = targetType(
       messager,
@@ -174,7 +184,7 @@ public class JsonClassCodegenProcessor : AbstractProcessor() {
       }
     }
 
-    return AdapterGenerator(type, sortedProperties)
+    return AdapterGenerator(type, sortedProperties, readOnly, writeOnly)
   }
 }
 

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

@@ -89,7 +89,7 @@ private class JsonClassSymbolProcessor(
 
       try {
         val originatingFile = type.containingFile!!
-        val adapterGenerator = adapterGenerator(logger, resolver, type) ?: return emptyList()
+        val adapterGenerator = adapterGenerator(logger, resolver, type, jsonClassAnnotation.readOnly, jsonClassAnnotation.writeOnly) ?: return emptyList()
         val preparedAdapter = adapterGenerator
           .prepare(generateProguardRules) { spec ->
             spec.toBuilder()
@@ -114,6 +114,8 @@ private class JsonClassSymbolProcessor(
     logger: KSPLogger,
     resolver: Resolver,
     originalType: KSDeclaration,
+    readOnly: Boolean,
+    writeOnly: Boolean,
   ): AdapterGenerator? {
     val type = targetType(originalType, resolver, logger) ?: return null
 
@@ -142,7 +144,7 @@ private class JsonClassSymbolProcessor(
       }
     }
 
-    return AdapterGenerator(type, sortedProperties)
+    return AdapterGenerator(type, sortedProperties, readOnly, writeOnly)
   }
 }
 

moshi-kotlin-codegen/src/test/java/com/squareup/moshi/kotlin/codegen/apt/JsonClassCodegenProcessorTest.kt

@@ -537,6 +537,75 @@ class JsonClassCodegenProcessorTest {
     )
   }
 
+  @Test
+  fun `ReadOnly adapter should throw on read`() {
+    val result = compile(
+      kotlin(
+        "source.kt",
+        """
+      import com.squareup.moshi.JsonClass
+      typealias FirstName = String
+      typealias LastName = String
+      @JsonClass(generateAdapter = true, readOnly = true)
+      data class Person(val firstName: FirstName, val lastName: LastName, val hairColor: String)
+      """,
+      ),
+    )
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
+
+    result.generatedFiles.filter { it.name == "PersonJsonAdapter.kt" }.forEach { generatedFile ->
+      assertThat(generatedFile.readText()).contains(
+        """
+      throw UnsupportedOperationException(buildString(79) {
+      append("GeneratedJsonAdapter(").append("Person").append(')').append(" is read only. @JsonClass is set with readOnly=true")
+      })""",
+      )
+    }
+  }
+
+  @Test
+  fun `WriteOnly adapter should throw on write`() {
+    val result = compile(
+      kotlin(
+        "source.kt",
+        """
+      import com.squareup.moshi.JsonClass
+      typealias FirstName = String
+      typealias LastName = String
+      @JsonClass(generateAdapter = true, writeOnly = true)
+      data class Person(val firstName: FirstName, val lastName: LastName, val hairColor: String)
+      """,
+      ),
+    )
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
+    result.generatedFiles.filter { it.name == "PersonJsonAdapter.kt" }.forEach { generatedFile ->
+      assertThat(generatedFile.readText()).contains(
+        """
+      throw UnsupportedOperationException(buildString(81) {
+      append("GeneratedJsonAdapter(").append("Person").append(')').append(" is write only. @JsonClass is set with writeOnly=true")
+      })""",
+      )
+    }
+  }
+
+  @Test
+  fun `Adapter can't be readOnly and writeOnly`() {
+    val result = compile(
+      kotlin(
+        "source.kt",
+        """
+      import com.squareup.moshi.JsonClass
+      typealias FirstName = String
+      typealias LastName = String
+      @JsonClass(generateAdapter = true, writeOnly = true, readOnly = true)
+      data class Person(val firstName: FirstName, val lastName: LastName, val hairColor: String)
+      """,
+      ),
+    )
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.COMPILATION_ERROR)
+    assertThat(result.messages).contains("@JsonClass can't be both readOnly and writeOnly")
+  }
+
   @Test
   fun `Processor should generate comprehensive proguard rules`() {
     val result = compile(

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

@@ -64,4 +64,19 @@ public annotation class JsonClass(
    * expected signature.
    */
   val generator: String = "",
+  /**
+   * An optional parameter that replace generated toJson() code of the adapter to simply throw a
+   * {@link JsonDataException}.
+   *
+   * <p>Reduce generated code size when data is never serialized to JSON.
+   */
+  val readOnly: Boolean = false,
+
+  /**
+   * An optional parameter that replace generated fromJson() code of the adapter to simply throw a
+   * {@link JsonDataException}.
+   *
+   * <p>Reduce generated code size when data is never deserialized from JSON.
+   */
+  val writeOnly: Boolean = false,
 )