RNGP - Introduce enableCodegenInApps

Summary:
This is part of a series of tasks to make the React Native Gradle Plugin (RNGP) variant-aware.

Historically we used to enable the codegen only for library modules. This is not working well for apps like RN Tester which don't have library modules but are running the codegen.

Therefore I'm introducing the `enableCodegenInApps` that is allowing apps to turn off the codegen if needed.

Changelog:
[Internal] [Changed] - RNGP - Introduce enableCodegenInApps

Reviewed By: cipolleschi

Differential Revision: D40633106

fbshipit-source-id: dc2ae9bbfe5b7940f9e9fe505ab2198a42c8a3f6

Author: cortinico

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/ReactExtension.kt

@@ -221,4 +221,11 @@ abstract class ReactExtension @Inject constructor(project: Project) {
    */
   val codegenJavaPackageName: Property<String> =
       objects.property(String::class.java).convention("com.facebook.fbreact.specs")
+
+  /**
+   * Toggles the Codegen for App modules. By default we enable the codegen only for library modules.
+   * If you want to enable codegen in your app, you will have to set this to true. Default: false
+   */
+  val enableCodegenInApps: Property<Boolean> =
+      objects.property(Boolean::class.java).convention(false)
 }

packages/react-native-gradle-plugin/src/main/kotlin/com/facebook/react/ReactPlugin.kt

@@ -9,7 +9,6 @@ package com.facebook.react
 
 import com.android.build.api.variant.AndroidComponentsExtension
 import com.android.build.gradle.AppExtension
-import com.android.build.gradle.LibraryExtension
 import com.android.build.gradle.internal.tasks.factory.dependsOn
 import com.facebook.react.tasks.BuildCodegenCLITask
 import com.facebook.react.tasks.GenerateCodegenArtifactsTask
@@ -21,7 +20,6 @@ import com.facebook.react.utils.NdkConfiguratorUtils.configureReactNativeNdk
 import com.facebook.react.utils.findPackageJsonFile
 import java.io.File
 import kotlin.system.exitProcess
-import org.gradle.api.Action
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.Task
@@ -31,8 +29,25 @@ class ReactPlugin : Plugin<Project> {
   override fun apply(project: Project) {
     checkJvmVersion(project)
     val extension = project.extensions.create("react", ReactExtension::class.java, project)
-    applyAppPlugin(project, extension)
-    applyCodegenPlugin(project, extension)
+
+    // App Only Configuration
+    project.pluginManager.withPlugin("com.android.application") {
+      configureReactNativeNdk(project, extension)
+      configureBuildConfigFields(project)
+      configureDevPorts(project)
+
+      project.afterEvaluate {
+        project.extensions.getByType(AppExtension::class.java).applicationVariants.all {
+          project.configureReactTasks(variant = it, config = extension)
+        }
+      }
+      configureCodegen(project, extension, isLibrary = false)
+    }
+
+    // Library Only Configuration
+    project.pluginManager.withPlugin("com.android.library") {
+      configureCodegen(project, extension, isLibrary = true)
+    }
   }
 
   private fun checkJvmVersion(project: Project) {
@@ -54,30 +69,12 @@ class ReactPlugin : Plugin<Project> {
     }
   }
 
-  private fun applyAppPlugin(project: Project, config: ReactExtension) {
-    project.pluginManager.withPlugin("com.android.application") {
-      configureReactNativeNdk(project, config)
-      configureBuildConfigFields(project)
-      configureDevPorts(project)
-      project.afterEvaluate {
-        val isAndroidLibrary = project.plugins.hasPlugin("com.android.library")
-        val variants =
-            if (isAndroidLibrary) {
-              project.extensions.getByType(LibraryExtension::class.java).libraryVariants
-            } else {
-              project.extensions.getByType(AppExtension::class.java).applicationVariants
-            }
-        variants.all { project.configureReactTasks(variant = it, config = config) }
-      }
-    }
-  }
-
   /**
    * A plugin to enable react-native-codegen in Gradle environment. See the Gradle API docs for more
    * information: https://docs.gradle.org/current/javadoc/org/gradle/api/Project.html
    */
   @Suppress("UnstableApiUsage")
-  private fun applyCodegenPlugin(project: Project, extension: ReactExtension) {
+  private fun configureCodegen(project: Project, extension: ReactExtension, isLibrary: Boolean) {
     // First, we set up the output dir for the codegen.
     val generatedSrcDir = File(project.buildDir, "generated/source/codegen")
 
@@ -86,6 +83,7 @@ class ReactPlugin : Plugin<Project> {
           it.codegenDir.set(extension.codegenDir)
           val bashWindowsHome = project.findProperty("REACT_WINDOWS_BASH") as String?
           it.bashWindowsHome.set(bashWindowsHome)
+          it.onlyIf { isLibrary || extension.enableCodegenInApps.get() }
         }
 
     // We create the task to produce schema from JS files.
@@ -96,6 +94,7 @@ class ReactPlugin : Plugin<Project> {
               it.nodeExecutableAndArgs.set(extension.nodeExecutableAndArgs)
               it.codegenDir.set(extension.codegenDir)
               it.generatedSrcDir.set(generatedSrcDir)
+              it.onlyIf { isLibrary || extension.enableCodegenInApps.get() }
 
               // We're reading the package.json at configuration time to properly feed
               // the `jsRootDir` @Input property of this task. Therefore, the
@@ -123,6 +122,7 @@ class ReactPlugin : Plugin<Project> {
               it.packageJsonFile.set(findPackageJsonFile(project, extension))
               it.codegenJavaPackageName.set(extension.codegenJavaPackageName)
               it.libraryName.set(extension.libraryName)
+              it.onlyIf { isLibrary || extension.enableCodegenInApps.get() }
             }
 
     // We update the android configuration to include the generated sources.
@@ -133,12 +133,8 @@ class ReactPlugin : Plugin<Project> {
       ext.sourceSets.getByName("main").java.srcDir(File(generatedSrcDir, "java"))
     }
 
-    // `preBuild` is one of the base tasks automatically registered by Gradle.
+    // `preBuild` is one of the base tasks automatically registered by AGP.
     // This will invoke the codegen before compiling the entire project.
-    val androidPluginHandler = Action { _: Plugin<*> ->
-      project.tasks.named("preBuild", Task::class.java).dependsOn(generateCodegenArtifactsTask)
-    }
-    project.plugins.withId("com.android.application", androidPluginHandler)
-    project.plugins.withId("com.android.library", androidPluginHandler)
+    project.tasks.named("preBuild", Task::class.java).dependsOn(generateCodegenArtifactsTask)
   }
 }

packages/rn-tester/android/app/build.gradle

@@ -88,6 +88,7 @@ react {
     // Codegen Configs
     reactNativeDir = rootDir
     codegenDir = new File(rootDir, "node_modules/react-native-codegen")
+    enableCodegenInApps = true
 }
 
 /**