Add DSL helpers to enable metrics and reports

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodComposeExtension.kt

@@ -15,12 +15,9 @@
  */
 package app.cash.redwood.gradle
 
-import javax.inject.Inject
-import org.gradle.api.model.ObjectFactory
 import org.gradle.api.provider.Property
 
-public abstract class RedwoodComposeExtension
-@Inject constructor(objectFactory: ObjectFactory) {
+public interface RedwoodComposeExtension {
   /**
    * The version of the JetBrains Compose compiler to use, or a Maven coordinate triple of
    * the custom Compose compiler to use.
@@ -39,7 +36,35 @@ public abstract class RedwoodComposeExtension
    * }
    * ```
    */
-  public val kotlinCompilerPlugin: Property<String> =
-    objectFactory.property(String::class.java)
-      .convention(composeCompilerVersion)
+  public val kotlinCompilerPlugin: Property<String>
+
+  /**
+   * Enable the output of metrics from the Compose compiler.
+   *
+   * Text files will be written to `generated/redwood/compose-metrics/` in the project's build
+   * directory. See
+   * [the compiler documentation](https://github.com/androidx/androidx/blob/androidx-main/compose/compiler/design/compiler-metrics.md#reports-breakdown)
+   * for more information about the contents.
+   *
+   * **NOTE:** This should only be enabled during investigation as it breaks the use of
+   * Gradle's build cache for this project's Kotlin compilation tasks.
+   *
+   * @see enableReports
+   */
+  public fun enableMetrics()
+
+  /**
+   * Enable the output of reports from the Compose compiler.
+   *
+   * Text files will be written to `generated/redwood/compose-reports/` in the project's build
+   * directory. See
+   * [the compiler documentation](https://github.com/androidx/androidx/blob/androidx-main/compose/compiler/design/compiler-metrics.md#reports-breakdown)
+   * for more information about the contents.
+   *
+   * **NOTE:** This should only be enabled during investigation as it breaks the use of
+   * Gradle's build cache for this project's Kotlin compilation tasks.
+   *
+   * @see enableMetrics
+   */
+  public fun enableReports()
 }

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodComposeExtensionImpl.kt

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2023 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
+ *
+ *      http://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 app.cash.redwood.gradle
+
+import org.gradle.api.Project
+import org.gradle.api.provider.Property
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+internal class RedwoodComposeExtensionImpl(private val project: Project) : RedwoodComposeExtension {
+  private var metricsEnabled = false
+  private var reportsEnabled = false
+
+  // Explicit backing property avoids Gradle attempting to reflect on an implicit backing field.
+  override val kotlinCompilerPlugin: Property<String> get() = _kotlinCompilerPlugin
+  private val _kotlinCompilerPlugin = project.objects.property(String::class.java)
+    .convention(composeCompilerVersion)
+
+  override fun enableMetrics() {
+    if (metricsEnabled) return
+    metricsEnabled = true
+
+    project.tasks.withType(KotlinCompile::class.java) {
+      val dir = project.redwoodGeneratedDir("compose-metrics/${it.name}").get().asFile.absolutePath
+      it.compilerOptions.freeCompilerArgs.addAll(
+        "-P",
+        "plugin:androidx.compose.compiler.plugins.kotlin:metricsDestination=$dir",
+      )
+    }
+  }
+
+  override fun enableReports() {
+    if (reportsEnabled) return
+    reportsEnabled = true
+
+    project.tasks.withType(KotlinCompile::class.java) {
+      val dir = project.redwoodGeneratedDir("compose-reports/${it.name}").get().asFile.absolutePath
+      it.compilerOptions.freeCompilerArgs.addAll(
+        "-P",
+        "plugin:androidx.compose.compiler.plugins.kotlin:reportsDestination=$dir",
+      )
+    }
+  }
+}

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodComposePlugin.kt

@@ -38,7 +38,12 @@ public class RedwoodComposePlugin : KotlinCompilerPluginSupportPlugin {
   override fun apply(target: Project) {
     super.apply(target)
 
-    extension = target.extensions.create(extensionName, RedwoodComposeExtension::class.java)
+    extension = RedwoodComposeExtensionImpl(target)
+    target.extensions.add(
+      RedwoodComposeExtension::class.java,
+      extensionName,
+      extension,
+    )
 
     target.plugins.withId("org.jetbrains.compose") {
       throw IllegalStateException(

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodGeneratorPlugin.kt

@@ -88,7 +88,7 @@ public abstract class RedwoodGeneratorPlugin(
       it.description = "Generate Redwood Kotlin sources"
 
       it.toolClasspath.from(toolingConfiguration)
-      it.outputDir.set(project.layout.buildDirectory.dir("generated/redwood"))
+      it.outputDir.set(project.redwoodGeneratedDir("sources"))
       it.generatorFlag.set(strategy.generatorFlag)
       it.schemaType.set(extension.type)
       it.classpath.from(schemaConfiguration)

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/RedwoodSchemaPlugin.kt

@@ -62,7 +62,7 @@ public class RedwoodSchemaPlugin : Plugin<Project> {
       it.description = "Generate parsed schema JSON"
 
       it.toolClasspath.from(toolingConfiguration)
-      it.outputDir.set(project.layout.buildDirectory.dir("generated/redwood"))
+      it.outputDir.set(project.redwoodGeneratedDir("schema-json"))
       it.schemaType.set(extension.type)
       it.classpath.from(classpath, compilation.output.classesDirs)
     }

redwood-gradle-plugin/src/main/kotlin/app/cash/redwood/gradle/util.kt

@@ -16,6 +16,8 @@
 package app.cash.redwood.gradle
 
 import org.gradle.api.Project
+import org.gradle.api.file.Directory
+import org.gradle.api.provider.Provider
 
 internal fun Project.redwoodDependency(artifactId: String): Any {
   // Indicates when the plugin is applied inside the Redwood repo to Redwood's own modules. This
@@ -28,3 +30,7 @@ internal fun Project.redwoodDependency(artifactId: String): Any {
     "app.cash.redwood:$artifactId:$redwoodVersion"
   }
 }
+
+internal fun Project.redwoodGeneratedDir(name: String): Provider<Directory> {
+  return layout.buildDirectory.dir("generated/redwood/$name")
+}