Add @Json.ignore (#1417)

* Default Json.name to an unset value

* Promote shared transient tests to DualKotlinTest

* Add new ignore property to Json

* Support it in ClassJsonAdapter

* Mention no enum/record support

* Support in KotlinJsonAdapter

* Rework code gen API to know of "ignored"

* Support in apt code gen

* Support in KSP

* Update old non-working transient example test

* Synthetic holders

* Use field on both

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

@@ -26,5 +26,6 @@ public data class TargetParameter(
   val type: TypeName,
   val hasDefault: Boolean,
   val jsonName: String? = null,
+  val jsonIgnore: Boolean = false,
   val qualifiers: Set<AnnotationSpec>? = null
 )

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

@@ -25,7 +25,8 @@ public data class TargetProperty(
   val propertySpec: PropertySpec,
   val parameter: TargetParameter?,
   val visibility: KModifier,
-  val jsonName: String?
+  val jsonName: String?,
+  val jsonIgnore: Boolean
 ) {
   val name: String get() = propertySpec.name
   val type: TypeName get() = propertySpec.type

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

@@ -64,6 +64,7 @@ import javax.tools.Diagnostic.Kind.WARNING
 
 private val JSON_QUALIFIER = JsonQualifier::class.java
 private val JSON = Json::class.asClassName()
+private val TRANSIENT = Transient::class.asClassName()
 private val OBJECT_CLASS = ClassName("java.lang", "Object")
 private val VISIBILITY_MODIFIERS = setOf(
   KModifier.INTERNAL,
@@ -95,7 +96,8 @@ internal fun primaryConstructor(
       type = parameter.type,
       hasDefault = parameter.defaultValue != null,
       qualifiers = parameter.annotations.qualifiers(messager, elements),
-      jsonName = parameter.annotations.jsonName()
+      jsonName = parameter.annotations.jsonName(),
+      jsonIgnore = parameter.annotations.jsonIgnore(),
     )
   }
 
@@ -386,7 +388,6 @@ private fun declaredProperties(
   currentClass: ClassName,
   resolvedTypes: List<ResolvedTypeMapping>
 ): Map<String, TargetProperty> {
-
   val result = mutableMapOf<String, TargetProperty>()
   for (initialProperty in kotlinApi.propertySpecs) {
     val resolvedType = resolveTypeArgs(
@@ -398,19 +399,22 @@ private fun declaredProperties(
     val property = initialProperty.toBuilder(type = resolvedType).build()
     val name = property.name
     val parameter = constructor.parameters[name]
+    val isIgnored = property.annotations.any { it.typeName == TRANSIENT } ||
+      parameter?.jsonIgnore == true ||
+      property.annotations.jsonIgnore()
     result[name] = TargetProperty(
       propertySpec = property,
       parameter = parameter,
       visibility = property.modifiers.visibility(),
       jsonName = parameter?.jsonName ?: property.annotations.jsonName()
-        ?: name.escapeDollarSigns()
+        ?: name.escapeDollarSigns(),
+      jsonIgnore = isIgnored
     )
   }
 
   return result
 }
 
-private val TargetProperty.isTransient get() = propertySpec.annotations.any { it.typeName == Transient::class.asClassName() }
 private val TargetProperty.isSettable get() = propertySpec.mutable || parameter != null
 private val TargetProperty.isVisible: Boolean
   get() {
@@ -429,11 +433,11 @@ internal fun TargetProperty.generator(
   elements: Elements,
   instantiateAnnotations: Boolean
 ): PropertyGenerator? {
-  if (isTransient) {
+  if (jsonIgnore) {
     if (!hasDefault) {
       messager.printMessage(
         ERROR,
-        "No default value for transient property $name",
+        "No default value for transient/ignored property $name",
         sourceElement
       )
       return null
@@ -510,16 +514,36 @@ private fun List<AnnotationSpec>?.qualifiers(
 
 private fun List<AnnotationSpec>?.jsonName(): String? {
   if (this == null) return null
-  return find { it.typeName == JSON }?.let { annotation ->
-    val mirror = requireNotNull(annotation.tag<AnnotationMirror>()) {
-      "Could not get the annotation mirror from the annotation spec"
-    }
-    mirror.elementValues.entries.single {
-      it.key.simpleName.contentEquals("name")
-    }.value.value as String
+  return filter { it.typeName == JSON }.firstNotNullOfOrNull { annotation ->
+    annotation.jsonName()
   }
 }
 
+private fun List<AnnotationSpec>?.jsonIgnore(): Boolean {
+  if (this == null) return false
+  return filter { it.typeName == JSON }.firstNotNullOfOrNull { annotation ->
+    annotation.jsonIgnore()
+  } ?: false
+}
+
+private fun AnnotationSpec.jsonName(): String? {
+  return elementValue<String>("name").takeUnless { it == Json.UNSET_NAME }
+}
+
+private fun AnnotationSpec.jsonIgnore(): Boolean {
+  return elementValue<Boolean>("ignore") ?: false
+}
+
+private fun <T> AnnotationSpec.elementValue(name: String): T? {
+  val mirror = requireNotNull(tag<AnnotationMirror>()) {
+    "Could not get the annotation mirror from the annotation spec"
+  }
+  @Suppress("UNCHECKED_CAST")
+  return mirror.elementValues.entries.firstOrNull {
+    it.key.simpleName.contentEquals(name)
+  }?.value?.value as? T
+}
+
 private fun String.escapeDollarSigns(): String {
   return replace("\$", "\${\'\$\'}")
 }

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

@@ -21,14 +21,12 @@ import com.google.devtools.ksp.symbol.KSClassDeclaration
 import com.google.devtools.ksp.symbol.KSDeclaration
 import com.squareup.kotlinpoet.AnnotationSpec
 import com.squareup.kotlinpoet.KModifier
-import com.squareup.kotlinpoet.asClassName
 import com.squareup.moshi.JsonQualifier
 import com.squareup.moshi.kotlin.codegen.api.DelegateKey
 import com.squareup.moshi.kotlin.codegen.api.PropertyGenerator
 import com.squareup.moshi.kotlin.codegen.api.TargetProperty
 import com.squareup.moshi.kotlin.codegen.api.rawType
 
-private val TargetProperty.isTransient get() = propertySpec.annotations.any { it.typeName == Transient::class.asClassName() }
 private val TargetProperty.isSettable get() = propertySpec.mutable || parameter != null
 private val TargetProperty.isVisible: Boolean
   get() {
@@ -47,10 +45,10 @@ internal fun TargetProperty.generator(
   originalType: KSDeclaration,
   instantiateAnnotations: Boolean
 ): PropertyGenerator? {
-  if (isTransient) {
+  if (jsonIgnore) {
     if (!hasDefault) {
       logger.error(
-        "No default value for transient property $name",
+        "No default value for transient/ignored property $name",
         originalType
       )
       return null

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

@@ -213,7 +213,11 @@ private fun KSAnnotated?.qualifiers(resolver: Resolver): Set<AnnotationSpec> {
 }
 
 private fun KSAnnotated?.jsonName(): String? {
-  return this?.findAnnotationWithType<Json>()?.name
+  return this?.findAnnotationWithType<Json>()?.name?.takeUnless { it == Json.UNSET_NAME }
+}
+
+private fun KSAnnotated?.jsonIgnore(): Boolean {
+  return this?.findAnnotationWithType<Json>()?.ignore ?: false
 }
 
 private fun declaredProperties(
@@ -223,7 +227,6 @@ private fun declaredProperties(
   resolver: Resolver,
   typeParameterResolver: TypeParameterResolver,
 ): Map<String, TargetProperty> {
-
   val result = mutableMapOf<String, TargetProperty>()
   for (property in classDecl.getDeclaredProperties()) {
     val initialType = property.type.resolve()
@@ -235,12 +238,14 @@ private fun declaredProperties(
     val propertySpec = property.toPropertySpec(resolver, resolvedType, typeParameterResolver)
     val name = propertySpec.name
     val parameter = constructor.parameters[name]
+    val isTransient = property.isAnnotationPresent(Transient::class)
     result[name] = TargetProperty(
       propertySpec = propertySpec,
       parameter = parameter,
       visibility = property.getVisibility().toKModifier() ?: KModifier.PUBLIC,
       jsonName = parameter?.jsonName ?: property.jsonName()
-        ?: name.escapeDollarSigns()
+        ?: name.escapeDollarSigns(),
+      jsonIgnore = isTransient || parameter?.jsonIgnore == true || property.jsonIgnore()
     )
   }
 

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

@@ -334,7 +334,27 @@ class JsonClassCodegenProcessorTest(
     )
     assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.COMPILATION_ERROR)
     assertThat(result.messages).contains(
-      "error: No default value for transient property a"
+      "error: No default value for transient/ignored property a"
+    )
+  }
+
+  @Test
+  fun requiredIgnoredConstructorParameterFails() {
+    val result = compile(
+      kotlin(
+        "source.kt",
+        """
+          import com.squareup.moshi.Json
+          import com.squareup.moshi.JsonClass
+
+          @JsonClass(generateAdapter = true)
+          class RequiredIgnoredConstructorParameter(@Json(ignore = true) var a: Int)
+          """
+      )
+    )
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.COMPILATION_ERROR)
+    assertThat(result.messages).contains(
+      "error: No default value for transient/ignored property a"
     )
   }
 

kotlin/codegen/src/test/java/com/squareup/moshi/kotlin/codegen/ksp/JsonClassSymbolProcessorTest.kt

@@ -357,7 +357,28 @@ class JsonClassSymbolProcessorTest(
     )
     assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.COMPILATION_ERROR)
     assertThat(result.messages).contains(
-      "No default value for transient property a"
+      "No default value for transient/ignored property a"
+    )
+  }
+
+  @Test
+  fun requiredIgnoredConstructorParameterFails() {
+    val result = compile(
+      kotlin(
+        "source.kt",
+        """
+          package test
+          import com.squareup.moshi.Json
+          import com.squareup.moshi.JsonClass
+
+          @JsonClass(generateAdapter = true)
+          class RequiredTransientConstructorParameter(@Json(ignore = true) var a: Int)
+          """
+      )
+    )
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.COMPILATION_ERROR)
+    assertThat(result.messages).contains(
+      "No default value for transient/ignored property a"
     )
   }