introduce Kotlin convention plugins for java and android libraries

This pulls compiler configurations into a single location, except for friend paths.

Also introduces the Kotlin bom platform dependency to ensure a single Kotlin version.

Author: RBusarow

benchmarks/performance-poetry/complex-poetry/build.gradle.kts

@@ -1,6 +1,6 @@
 plugins {
   id("com.android.application")
-  kotlin("android")
+  `kotlin-android`
   id("kotlin-parcelize")
 }
 android {

build.gradle.kts

@@ -1,5 +1,4 @@
 import org.jetbrains.dokka.gradle.DokkaTask
-import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 import org.jlleitschuh.gradle.ktlint.KtlintExtension
 import org.jlleitschuh.gradle.ktlint.reporter.ReporterType
 
@@ -31,9 +30,6 @@ plugins {
   `dependency-guard`
 }
 
-// See https://stackoverflow.com/questions/25324880/detect-ide-environment-with-gradle
-val isRunningFromIde get() = project.properties["android.injected.invoked.from.ide"] == "true"
-
 subprojects {
 
   apply(plugin = "org.jlleitschuh.gradle.ktlint")
@@ -45,21 +41,6 @@ subprojects {
     }
   }
 
-  tasks.withType<KotlinCompile> {
-    kotlinOptions {
-      // Allow warnings when running from IDE, makes it easier to experiment.
-      if (!isRunningFromIde) {
-        allWarningsAsErrors = true
-      }
-
-      jvmTarget = "1.8"
-
-      // Don't panic, all this does is allow us to use the @OptIn meta-annotation.
-      // to define our own experiments.
-      freeCompilerArgs += "-opt-in=kotlin.RequiresOptIn"
-    }
-  }
-
   // Configuration documentation: https://github.com/JLLeitschuh/ktlint-gradle#configuration
   configure<KtlintExtension> {
     // Prints the name of failed rules.
@@ -73,35 +54,6 @@ subprojects {
 
 apply(from = rootProject.file(".buildscript/binary-validation.gradle"))
 
-// Require explicit public modifiers and types for actual library modules, not samples.
-allprojects.filterNot {
-  it.path.startsWith(":samples") ||
-    it.path.startsWith(":benchmarks")
-}
-  .forEach {
-    it.tasks.withType<KotlinCompile>().configureEach {
-      // Tests and benchmarks aren't part of the public API, don't turn explicit API mode on for
-      // them.
-      if (!name.contains("test", ignoreCase = true) &&
-        !name.contains("jmh", ignoreCase = true)
-      ) {
-        kotlinOptions {
-          // TODO this should be moved to `kotlin { explicitApi() }` once that's working for android
-          //  projects, see https://youtrack.jetbrains.com/issue/KT-37652.
-          @Suppress("SuspiciousCollectionReassignment")
-          freeCompilerArgs += "-Xexplicit-api=strict"
-
-          // Make sure our module names don't conflict with those from pre-workflow1
-          // releases, so that old and new META-INF/ entries don't stomp each other.
-          // (This is only an issue for apps that are still migrating from workflow to
-          // workflow1, and so need to import two versions of the library.)
-          // https://blog.jetbrains.com/kotlin/2015/09/kotlin-m13-is-out/
-          moduleName = "wf1-${it.name}"
-        }
-      }
-    }
-  }
-
 // This plugin needs to be applied to the root projects for the dokkaGfmCollector task we use to
 // generate the documentation site.
 apply(plugin = "org.jetbrains.dokka")

buildSrc/build.gradle.kts

@@ -10,6 +10,9 @@ repositories {
 }
 
 dependencies {
+
+  implementation(platform(libs.kotlin.bom))
+
   compileOnly(gradleApi())
 
   implementation(libs.android.gradle.plugin)

buildSrc/src/main/java/com/squareup/workflow1/buildsrc/KotlinCommonSettings.kt

@@ -0,0 +1,56 @@
+package com.squareup.workflow1.buildsrc
+
+import org.gradle.api.Project
+import org.gradle.kotlin.dsl.dependencies
+import org.gradle.kotlin.dsl.kotlin
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+// See https://stackoverflow.com/questions/25324880/detect-ide-environment-with-gradle
+val Project.isRunningFromIde
+  get() = properties["android.injected.invoked.from.ide"] == "true"
+
+@Suppress("SuspiciousCollectionReassignment")
+fun Project.kotlinCommonSettings(
+  compileTask: KotlinCompile
+) {
+
+  // force the same Kotlin version everywhere, including transitive dependencies
+  dependencies {
+    "implementation"(platform(kotlin("bom")))
+  }
+
+  compileTask.kotlinOptions {
+
+    // Allow warnings when running from IDE, makes it easier to experiment.
+    if (!isRunningFromIde) {
+      allWarningsAsErrors = true
+    }
+
+    // Don't panic, all this does is allow us to use the @OptIn meta-annotation.
+    // to define our own experiments.
+    freeCompilerArgs += "-opt-in=kotlin.RequiresOptIn"
+
+    // Make sure our module names don't conflict with those from pre-workflow1
+    // releases, so that old and new META-INF/ entries don't stomp each other.
+    // (This is only an issue for apps that are still migrating from workflow to
+    // workflow1, and so need to import two versions of the library.)
+    // https://blog.jetbrains.com/kotlin/2015/09/kotlin-m13-is-out/
+    moduleName = "wf1-${project.name}"
+  }
+
+  maybeEnableExplicitApi(compileTask)
+}
+
+private fun Project.maybeEnableExplicitApi(compileTask: KotlinCompile) {
+  when {
+    path.startsWith(":samples") -> return
+    path.startsWith(":benchmarks") -> return
+    compileTask.name.contains("test", ignoreCase = true) -> return
+    compileTask.name.contains("jmh", ignoreCase = true) -> return
+    else -> compileTask.kotlinOptions {
+      // TODO this should be moved to `kotlin { explicitApi() }` once that's working for android
+      //  projects, see https://youtrack.jetbrains.com/issue/KT-37652.
+      freeCompilerArgs += "-Xexplicit-api=strict"
+    }
+  }
+}

buildSrc/src/main/java/kotlin-android.gradle.kts

@@ -0,0 +1,19 @@
+import com.squareup.workflow1.buildsrc.kotlinCommonSettings
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+  kotlin("android")
+}
+
+extensions.getByType(JavaPluginExtension::class).apply {
+  sourceCompatibility = JavaVersion.VERSION_1_8
+  targetCompatibility = JavaVersion.VERSION_1_8
+}
+
+tasks.withType<KotlinCompile> {
+  kotlinOptions {
+    jvmTarget = "1.8"
+  }
+
+  project.kotlinCommonSettings(this)
+}

buildSrc/src/main/java/kotlin-jvm.gradle.kts

@@ -0,0 +1,19 @@
+import com.squareup.workflow1.buildsrc.kotlinCommonSettings
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+  kotlin("jvm")
+}
+
+extensions.getByType(JavaPluginExtension::class).apply {
+  sourceCompatibility = JavaVersion.VERSION_1_8
+  targetCompatibility = JavaVersion.VERSION_1_8
+}
+
+tasks.withType<KotlinCompile> {
+  kotlinOptions {
+    jvmTarget = "1.8"
+  }
+
+  project.kotlinCommonSettings(this)
+}

gradle/libs.versions.toml

@@ -169,6 +169,7 @@ jmh-gradle-plugin = "me.champeau.gradle:jmh-gradle-plugin:0.5.3"
 
 junit = { module = "junit:junit", version.ref = "jUnit" }
 
+kotlin-bom = { module = "org.jetbrains.kotlin:kotlin-bom", version.ref = "kotlin" }
 kotlin-common = { module = "org.jetbrains.kotlin:kotlin-stdlib-common", version.ref = "kotlin" }
 kotlin-gradle-plugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 kotlin-jdk6 = { module = "org.jetbrains.kotlin:kotlin-stdlib", version.ref = "kotlin" }

internal-testing-utils/build.gradle.kts

@@ -1,14 +1,9 @@
 plugins {
-  kotlin("jvm")
+  `kotlin-jvm`
 }
 
 apply(from = rootProject.file(".buildscript/configure-maven-publish.gradle"))
 
-java {
-  sourceCompatibility = JavaVersion.VERSION_1_8
-  targetCompatibility = JavaVersion.VERSION_1_8
-}
-
 dependencies {
   implementation(libs.kotlin.jdk8)
 

internal-testing-utils/dependencies/runtimeClasspath.txt

@@ -1,3 +1,4 @@
+org.jetbrains.kotlin:kotlin-bom:1.6.10
 org.jetbrains.kotlin:kotlin-stdlib-common:1.6.10
 org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.6.10
 org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.6.10

samples/compose-samples/build.gradle.kts

@@ -1,6 +1,6 @@
 plugins {
   id("com.android.application")
-  kotlin("android")
+  `kotlin-android`
 }
 
 apply(from = rootProject.file(".buildscript/android-sample-app.gradle"))