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Import response type keeper
This annotation processor parses all types used as response bodies in Retrofit service methods and adds a keep rule for them. This ensures that even if the type isn't used by callers, it is kept and used to parse the body.
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Diff for: ‎gradle/libs.versions.toml

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@@ -18,6 +18,8 @@ okhttp = "3.14.9"
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protobuf = "3.25.2"
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robovm = "2.3.14"
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kotlinx-serialization = "1.6.2"
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autoService = "1.1.1"
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incap = "1.0.0"
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[libraries]
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androidPlugin = { module = "com.android.tools.build:gradle", version = "8.2.2" }
@@ -41,6 +43,12 @@ protobufPlugin = "com.google.protobuf:protobuf-gradle-plugin:0.9.4"
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protobuf = { module = "com.google.protobuf:protobuf-java", version.ref = "protobuf" }
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protoc = { module = "com.google.protobuf:protoc", version.ref = "protobuf" }
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incap-runtime = { module = "net.ltgt.gradle.incap:incap", version.ref = "incap" }
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incap-processor = { module = "net.ltgt.gradle.incap:incap-processor", version.ref = "incap" }
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autoService-annotations = { module = "com.google.auto.service:auto-service-annotations", version.ref = "autoService" }
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autoService-compiler = { module = "com.google.auto.service:auto-service", version.ref = "autoService" }
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kotlinCoroutines = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version = "1.7.3" }
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kotlinx-serialization-core = { module = "org.jetbrains.kotlinx:kotlinx-serialization-core", version.ref = "kotlinx-serialization" }
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kotlinx-serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "kotlinx-serialization" }
@@ -71,3 +79,4 @@ jsoup = { module = "org.jsoup:jsoup", version = "1.17.2" }
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robovm = { module = "com.mobidevelop.robovm:robovm-rt", version.ref = "robovm" }
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googleJavaFormat = "com.google.googlejavaformat:google-java-format:1.19.2"
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ktlint = "com.pinterest.ktlint:ktlint-cli:1.1.1"
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compileTesting = "com.google.testing.compile:compile-testing:0.21.0"

Diff for: ‎retrofit-response-type-keeper/README.md

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# Response Type Keeper
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Generates keep rules for types mentioned in generic parameter positions of Retrofit service methods.
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## Problem
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Given a service method like
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```java
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@GET("users/{id}")
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Call<User> getUser(
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@Path("id") String id);
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```
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If you execute this request and do not actually use the returned `User` instance, R8 will remove it
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and replace the return type as `Call<?>`. This fails Retrofit's runtime validation since a wildcard
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is not a valid type to pass to a converter. Note: this removal only occurs if the Retrofit's service
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method definition is the only reference to `User`.
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## Solution
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This module contains an annotation processor which looks at each Retrofit method and generates
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explicit `-keep` rules for the types mentioned.
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Add it to Gradle Java projects with
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```groovy
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annotationProcessor 'com.squareup.retrofit2:response-type-keeper:<version>'
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```
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Or Gradle Kotlin projects with
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```groovy
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kapt 'com.squareup.retrofit2:response-type-keeper:<version>'
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```
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For other build systems, the `com.squareup.retrofit2:response-type-keeper` needs added to the Java
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compiler `-processor` classpath.
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For the example above, the annotation processor's generated file would contain
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```
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-keep com.example.User
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```
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This works for nested generics, such as `Call<ApiResponse<User>>`, which would produce:
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```
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-keep com.example.ApiResponse
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-keep com.example.User
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```
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It also works on Kotlin `suspend` functions which turn into a type like
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`Continuation<? extends User>` in the Java bytecode.

Diff for: ‎retrofit-response-type-keeper/build.gradle

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apply plugin: 'org.jetbrains.kotlin.jvm'
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apply plugin: 'org.jetbrains.kotlin.kapt'
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apply plugin: 'com.vanniktech.maven.publish'
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dependencies {
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compileOnly libs.autoService.annotations
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compileOnly libs.incap.runtime
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kapt libs.autoService.compiler
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kapt libs.incap.processor
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testImplementation libs.junit
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testImplementation libs.compileTesting
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testImplementation libs.truth
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testImplementation projects.retrofit
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}

Diff for: ‎retrofit-response-type-keeper/gradle.properties

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POM_ARTIFACT_ID=response-type-keeper
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POM_NAME=Response Type Keeper
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POM_DESCRIPTION=Annotation processor to generate R8 keep rules for types mentioned in generics.

Diff for: ‎retrofit-response-type-keeper/src/main/kotlin/retrofit2/keeper/RetrofitResponseTypeKeepProcessor.kt

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/*
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* Copyright (C) 2024 Square, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package retrofit2.keeper
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import com.google.auto.service.AutoService
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import javax.annotation.processing.AbstractProcessor
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import javax.annotation.processing.Processor
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import javax.annotation.processing.RoundEnvironment
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import javax.lang.model.SourceVersion
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import javax.lang.model.element.ExecutableElement
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import javax.lang.model.element.TypeElement
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import javax.lang.model.type.DeclaredType
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import javax.lang.model.type.TypeMirror
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import javax.lang.model.type.WildcardType
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import javax.tools.StandardLocation.CLASS_OUTPUT
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import net.ltgt.gradle.incap.IncrementalAnnotationProcessor
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import net.ltgt.gradle.incap.IncrementalAnnotationProcessorType.ISOLATING
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@AutoService(Processor::class)
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@IncrementalAnnotationProcessor(ISOLATING)
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class RetrofitResponseTypeKeepProcessor : AbstractProcessor() {
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override fun getSupportedSourceVersion() = SourceVersion.latestSupported()
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override fun getSupportedAnnotationTypes() = setOf(
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"retrofit2.http.DELETE",
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"retrofit2.http.GET",
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"retrofit2.http.HEAD",
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"retrofit2.http.HTTP",
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"retrofit2.http.OPTIONS",
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"retrofit2.http.PATCH",
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"retrofit2.http.POST",
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"retrofit2.http.PUT",
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)
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override fun process(
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annotations: Set<TypeElement>,
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roundEnv: RoundEnvironment,
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): Boolean {
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val elements = processingEnv.elementUtils
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val types = processingEnv.typeUtils
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val methods = supportedAnnotationTypes
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.mapNotNull(elements::getTypeElement)
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.flatMap(roundEnv::getElementsAnnotatedWith)
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val elementToReferencedTypes = mutableMapOf<TypeElement, MutableSet<String>>()
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for (method in methods) {
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val executableElement = method as ExecutableElement
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val serviceType = method.enclosingElement as TypeElement
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val referenced = elementToReferencedTypes.getOrPut(serviceType, ::LinkedHashSet)
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val returnType = executableElement.returnType as DeclaredType
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returnType.recursiveParameterizedTypesTo(referenced)
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// Retrofit has special support for 'suspend fun' in Kotlin which manifests as a
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// final Continuation parameter whose generic type is the declared return type.
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executableElement.parameters
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.lastOrNull()
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?.asType()
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?.takeIf { types.erasure(it).toString() == "kotlin.coroutines.Continuation" }
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?.let { (it as DeclaredType).typeArguments.single() }
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?.recursiveParameterizedTypesTo(referenced)
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}
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for ((element, referencedTypes) in elementToReferencedTypes) {
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val typeName = element.qualifiedName.toString()
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val outputFile = "META-INF/proguard/retrofit-response-type-keeper-$typeName.pro"
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val rules = processingEnv.filer.createResource(CLASS_OUTPUT, "", outputFile, element)
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rules.openWriter().buffered().use { w ->
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w.write("# $typeName\n")
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for (referencedType in referencedTypes.sorted()) {
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w.write("-keep,allowobfuscation,allowoptimization class $referencedType\n")
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}
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}
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}
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return false
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}
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private fun TypeMirror.recursiveParameterizedTypesTo(types: MutableSet<String>) {
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when (this) {
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is WildcardType -> {
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extendsBound?.recursiveParameterizedTypesTo(types)
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superBound?.recursiveParameterizedTypesTo(types)
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}
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is DeclaredType -> {
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for (typeArgument in typeArguments) {
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typeArgument.recursiveParameterizedTypesTo(types)
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}
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types += (asElement() as TypeElement).qualifiedName.toString()
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}
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}
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}
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}

Diff for: ‎retrofit-response-type-keeper/src/test/kotlin/retrofit2/keeper/RetrofitResponseTypeKeepProcessorTest.kt

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/*
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* Copyright (C) 2024 Square, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package retrofit2.keeper
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import com.google.common.truth.Truth.assertAbout
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import com.google.testing.compile.JavaFileObjects
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import com.google.testing.compile.JavaSourceSubjectFactory.javaSource
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import java.nio.charset.StandardCharsets.UTF_8
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import javax.tools.StandardLocation.CLASS_OUTPUT
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import org.junit.Test
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class RetrofitResponseTypeKeepProcessorTest {
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@Test
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fun allHttpMethods() {
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val service = JavaFileObjects.forSourceString(
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"test.Service",
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"""
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package test;
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import retrofit2.*;
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import retrofit2.http.*;
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class DeleteUser {}
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class GetUser {}
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class HeadUser {}
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class HttpUser {}
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class OptionsUser {}
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class PatchUser {}
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class PostUser {}
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class PutUser {}
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interface Service {
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@DELETE("/") Call<DeleteUser> delete();
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@GET("/") Call<GetUser> get();
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@HEAD("/") Call<HeadUser> head();
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@HTTP(method = "CUSTOM", path = "/") Call<HttpUser> http();
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@OPTIONS("/") Call<OptionsUser> options();
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@PATCH("/") Call<PatchUser> patch();
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@POST("/") Call<PostUser> post();
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@PUT("/") Call<PutUser> put();
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}
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""".trimIndent(),
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)
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assertAbout(javaSource())
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.that(service)
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.processedWith(RetrofitResponseTypeKeepProcessor())
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.compilesWithoutError()
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.and()
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.generatesFileNamed(
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CLASS_OUTPUT,
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"",
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"META-INF/proguard/retrofit-response-type-keeper-test.Service.pro",
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).withStringContents(
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UTF_8,
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"""
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|# test.Service
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|-keep,allowobfuscation,allowoptimization class retrofit2.Call
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|-keep,allowobfuscation,allowoptimization class test.DeleteUser
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|-keep,allowobfuscation,allowoptimization class test.GetUser
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|-keep,allowobfuscation,allowoptimization class test.HeadUser
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|-keep,allowobfuscation,allowoptimization class test.HttpUser
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|-keep,allowobfuscation,allowoptimization class test.OptionsUser
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|-keep,allowobfuscation,allowoptimization class test.PatchUser
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|-keep,allowobfuscation,allowoptimization class test.PostUser
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|-keep,allowobfuscation,allowoptimization class test.PutUser
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|
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""".trimMargin(),
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)
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}
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@Test
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fun nesting() {
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val service = JavaFileObjects.forSourceString(
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"test.Service",
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"""
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package test;
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import retrofit2.*;
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import retrofit2.http.*;
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class One<T> {}
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class Two<T> {}
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class Three {}
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interface Service {
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@GET("/") Call<One<Two<Three>>> get();
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}
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""".trimIndent(),
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)
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assertAbout(javaSource())
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.that(service)
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.processedWith(RetrofitResponseTypeKeepProcessor())
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.compilesWithoutError()
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.and()
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.generatesFileNamed(
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CLASS_OUTPUT,
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"",
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"META-INF/proguard/retrofit-response-type-keeper-test.Service.pro",
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).withStringContents(
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UTF_8,
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"""
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|# test.Service
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|-keep,allowobfuscation,allowoptimization class retrofit2.Call
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|-keep,allowobfuscation,allowoptimization class test.One
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|-keep,allowobfuscation,allowoptimization class test.Three
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|-keep,allowobfuscation,allowoptimization class test.Two
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|
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""".trimMargin(),
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)
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}
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@Test
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fun kotlinSuspend() {
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val service = JavaFileObjects.forSourceString(
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"test.Service",
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"""
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package test;
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import kotlin.coroutines.Continuation;
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import retrofit2.*;
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import retrofit2.http.*;
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class Body {}
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interface Service {
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@GET("/") Object get(Continuation<? extends Body> c);
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}
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""".trimIndent(),
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)
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assertAbout(javaSource())
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.that(service)
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.processedWith(RetrofitResponseTypeKeepProcessor())
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.compilesWithoutError()
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.and()
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.generatesFileNamed(
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CLASS_OUTPUT,
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"",
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"META-INF/proguard/retrofit-response-type-keeper-test.Service.pro",
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).withStringContents(
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UTF_8,
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"""
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|# test.Service
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|-keep,allowobfuscation,allowoptimization class java.lang.Object
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|-keep,allowobfuscation,allowoptimization class test.Body
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|
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""".trimMargin(),
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)
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}
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}

Diff for: ‎settings.gradle

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include ':retrofit-mock'
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include ':retrofit-response-type-keeper'
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include ':retrofit-adapters:guava'
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include ':retrofit-adapters:java8'
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include ':retrofit-adapters:rxjava'

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