build: Introduce Gradle Convention Plugins

AnkiDroid/build.gradle

@@ -1,8 +1,9 @@
 plugins {
     // Gradle plugin portal
     alias(libs.plugins.tripletPlay)
-    alias(libs.plugins.android.application)
-    alias(libs.plugins.kotlin.parcelize)
+    // TODO: migrate to .kts & replace the next 2 id lines with id("ankidroid.android.app")
+    id 'com.android.application'
+    id 'org.jetbrains.kotlin.plugin.parcelize'
     alias(libs.plugins.kotlin.serialization)
     alias(libs.plugins.keeper)
     alias(libs.plugins.roborazzi)

api/build.gradle.kts

@@ -2,28 +2,15 @@ import com.android.build.api.dsl.LibraryExtension
 import com.android.build.gradle.internal.tasks.factory.dependsOn
 
 plugins {
-    alias(libs.plugins.android.library)
+    id("ankidroid.android.api")
     id("maven-publish")
 }
 
 group = "com.ichi2.anki"
 version = "2.0.0"
 
-kotlin {
-    explicitApi()
-    compilerOptions {
-        // enable explicit api mode for additional checks related to the public api
-        // see https://kotlinlang.org/docs/whatsnew14.html#explicit-api-mode-for-library-authors
-        freeCompilerArgs.add("-Xexplicit-api=strict")
-    }
-}
-
 configure<LibraryExtension> {
     namespace = "com.ichi2.anki.api"
-    compileSdk =
-        libs.versions.compileSdk
-            .get()
-            .toInt()
 
     buildFeatures {
         buildConfig = true
@@ -55,11 +42,6 @@ configure<LibraryExtension> {
             proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
         }
     }
-    compileOptions {
-        // API remains on VERSION_11 for compatibility
-        sourceCompatibility = JavaVersion.VERSION_11
-        targetCompatibility = JavaVersion.VERSION_11
-    }
 
     publishing {
         singleVariant("release") {
@@ -69,8 +51,6 @@ configure<LibraryExtension> {
     }
 }
 
-apply(from = "../lint.gradle")
-
 dependencies {
     implementation(libs.androidx.annotation)
     implementation(libs.kotlin.stdlib)

build.gradle.kts

@@ -15,11 +15,13 @@ import kotlin.system.exitProcess
 
 // Top-level build file where you can add configuration options common to all subprojects/modules.
 plugins {
-    alias(libs.plugins.android.application) apply false
-    alias(libs.plugins.android.library) apply false
-    alias(libs.plugins.kotlin.android) apply false
-    alias(libs.plugins.kotlin.parcelize) apply false
-    alias(libs.plugins.kotlin.jvm) apply false
+    // Use `id` to avoid classpath conflicts. Versions are pinned by buildSrc/.
+    id("com.android.application") apply false
+    id("com.android.library") apply false
+    id("org.jetbrains.kotlin.android") apply false
+    id("org.jetbrains.kotlin.plugin.parcelize") apply false
+    id("org.jetbrains.kotlin.jvm") apply false
+    // Serialization is a separate artifact, not pinned transitively by AGP.
     alias(libs.plugins.kotlin.serialization) apply false
     alias(libs.plugins.ktlint.gradle.plugin) apply false
     alias(libs.plugins.keeper) apply false

buildSrc/README.md

@@ -11,4 +11,4 @@ outside the `.gradle.kts` build scripts.
   * NOTE: The overhead for one-off scripts is not worthwhile
 * Extracting build logic to support the [Gradle Configuration Cache](https://docs.gradle.org/current/userguide/configuration_cache.html)
   * Closures inside `.kts` files can capture an implicit `this` reference, which is CC-incompatible.
-* (Planned) Defining a convention plugin to reduce duplication in `.kts` files
+* Defining a convention plugin to reduce duplication in `.kts` files

buildSrc/build.gradle.kts

@@ -6,10 +6,19 @@ plugins {
 }
 
 repositories {
+    google()
     mavenCentral()
     gradlePluginPortal()
 }
 
+dependencies {
+    // Needed by precompiled script plugins that apply `com.android.library`.
+    // Pins AGP/KGP transitively, so call sites need `id("com.android.library")` etc. with no version.
+    implementation("com.android.tools.build:gradle:${libs.versions.androidGradlePlugin.get()}")
+    // Force the catalog version of KGP, otherwise it's overridden by AGP.
+    implementation("org.jetbrains.kotlin:kotlin-gradle-plugin:${libs.versions.kotlin.get()}")
+}
+
 configure<KtlintExtension> {
     version.set(libs.versions.ktlint.get())
 }

buildSrc/src/main/kotlin/ankidroid.android.api.gradle.kts

@@ -0,0 +1,55 @@
+/*
+ *  Copyright (c) 2026 David Allison <davidallisongithub@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// Convention plugin: Android library published as a public API artifact.
+//
+// Distinct from ankidroid.android-library:
+//   * Java source/target compat is 11 (not 17) for consumer compatibility.
+//   * Kotlin explicit-API strict mode is enabled (library-author quality check).
+//   * minSdk is not set.
+//
+// Publishing (maven-publish, singleVariant setup, POM metadata) is left to
+// the consuming module — it's intrinsically per-module configuration.
+
+import com.android.build.api.dsl.LibraryExtension
+import com.ichi2.anki.gradle.libsVersionFor
+import org.jetbrains.kotlin.gradle.dsl.KotlinAndroidProjectExtension
+
+plugins {
+    id("com.android.library")
+}
+
+extensions.configure<LibraryExtension> {
+    compileSdk = libsVersionFor("compileSdk").toInt()
+
+    compileOptions {
+        // API remains on VERSION_11 for consumer compatibility.
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
+}
+
+extensions.configure<KotlinAndroidProjectExtension> {
+    explicitApi()
+    compilerOptions {
+        // Stricter checks on public API shape for library authors.
+        // See https://kotlinlang.org/docs/whatsnew14.html#explicit-api-mode-for-library-authors
+        freeCompilerArgs.add("-Xexplicit-api=strict")
+    }
+}
+
+// Shared project-wide lint configuration.
+apply(from = "${rootDir}/lint.gradle")

buildSrc/src/main/kotlin/ankidroid.android.library.gradle.kts

@@ -0,0 +1,49 @@
+/*
+ *  Copyright (c) 2026 David Allison <davidallisongithub@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ Convention plugin: applies `com.android.library` and pins the settings
+ shared across every Android library module in this project.
+
+ This does not apply to the API module,
+ */
+
+import com.android.build.api.dsl.LibraryExtension
+import com.ichi2.anki.gradle.libsVersionFor
+
+plugins {
+    id("com.android.library")
+}
+
+extensions.configure<LibraryExtension> {
+    compileSdk = libsVersionFor("compileSdk").toInt()
+
+    defaultConfig {
+        minSdk = libsVersionFor("minSdk").toInt()
+    }
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_17
+        targetCompatibility = JavaVersion.VERSION_17
+    }
+}
+
+// Shared project-wide lint configuration.
+apply(from = "${rootDir}/lint.gradle")
+
+// Apply jacoco so module unit tests produce .exec files that
+// AnkiDroid's jacocoUnitTestReport aggregates across modules.
+apply(from = "${rootDir}/jacocoSupport.gradle")

buildSrc/src/main/kotlin/ankidroid.jvm.library.gradle.kts

@@ -0,0 +1,36 @@
+/*
+ *  Copyright (c) 2026 David Allison <davidallisongithub@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// Convention plugin: applies the Kotlin JVM plugin and pins Java/Kotlin
+// toolchain settings for pure-JVM (non-Android) modules in this project.
+
+import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+    id("org.jetbrains.kotlin.jvm")
+}
+
+tasks.withType(JavaCompile::class).configureEach {
+    sourceCompatibility = JavaVersion.VERSION_17.toString()
+    targetCompatibility = JavaVersion.VERSION_17.toString()
+}
+
+tasks.withType(KotlinCompile::class).configureEach {
+    compilerOptions {
+        jvmTarget = JvmTarget.JVM_17
+    }
+}

buildSrc/src/main/kotlin/com/ichi2/anki/gradle/VersionCatalogs.kt

@@ -0,0 +1,38 @@
+/*
+ *  Copyright (c) 2026 David Allison <davidallisongithub@gmail.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify it under
+ *  the terms of the GNU General Public License as published by the Free Software
+ *  Foundation; either version 3 of the License, or (at your option) any later
+ *  version.
+ *
+ *  This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ *  PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along with
+ *  this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.anki.gradle
+
+import org.gradle.api.Project
+import org.gradle.api.artifacts.VersionCatalog
+import org.gradle.api.artifacts.VersionCatalogsExtension
+import org.gradle.kotlin.dsl.getByType
+
+// Type-safe `libs` accessors aren't available in precompiled script plugins,
+// so read versions from the `libs` catalog explicitly.
+
+@Volatile
+private var cachedLibs: VersionCatalog? = null
+
+// A Project reference is required, so this can't be `by lazy { }`
+private fun Project.libs(): VersionCatalog =
+    cachedLibs ?: extensions
+        .getByType<VersionCatalogsExtension>()
+        .named("libs")
+        .also { cachedLibs = it }
+
+fun Project.libsVersionFor(alias: String): String =
+    libs().findVersion(alias).get().requiredVersion

common/android/build.gradle.kts

@@ -17,44 +17,13 @@
 import com.android.build.api.dsl.LibraryExtension
 
 plugins {
-    alias(libs.plugins.android.library)
+    id("ankidroid.android.library")
 }
 
 configure<LibraryExtension> {
     namespace = "com.ichi2.anki.common.android"
-    compileSdk =
-        libs.versions.compileSdk
-            .get()
-            .toInt()
-
-    defaultConfig {
-        minSdk =
-            libs.versions.minSdk
-                .get()
-                .toInt()
-        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
-        consumerProguardFiles("consumer-rules.pro")
-    }
-
-    buildTypes {
-        release {
-            isMinifyEnabled = true
-            proguardFiles(
-                getDefaultProguardFile("proguard-android-optimize.txt"),
-                "proguard-rules.pro",
-            )
-        }
-    }
-
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_17
-        targetCompatibility = JavaVersion.VERSION_17
-    }
 }
 
-apply(from = "../../lint.gradle")
-apply(from = "../../jacocoSupport.gradle")
-
 dependencies {
     implementation(project(":common"))
 

common/android/proguard-rules.pro

@@ -1,35 +0,0 @@
-# Add project specific ProGuard rules here.
-# You can control the set of applied configuration files using the
-# proguardFiles setting in build.gradle.
-#
-# For more details, see
-#   http://developer.android.com/guide/developing/tools/proguard.html
-
-# If your project uses WebView with JS, uncomment the following
-# and specify the fully qualified class name to the JavaScript interface
-# class:
-#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
-#   public *;
-#}
-
-# Uncomment this to preserve the line number information for
-# debugging stack traces.
-#-keepattributes SourceFile,LineNumberTable
-
-# If you keep the line number information, uncomment this to
-# hide the original source file name.
-#-renamesourcefileattribute SourceFile
-
-# FIXME remove this entire Android 4.2 workaround from 12/3/15 timrae commit for 2.15.x+
-# Samsung Android 4.2 bug workaround
-# https://code.google.com/p/android/issues/detail?id=78377
--keepattributes **
--keep class !android.support.v7.view.menu.**,!android.support.design.internal.NavigationMenu,!android.support.design.internal.NavigationMenuPresenter,!android.support.design.internal.NavigationSubMenu,** {*;}
-#5806 - Class: ActionBarOverflow
--keep public class android.support.v7.internal.view.menu.** { *; }
--keep public class androidx.appcompat.view.menu.** { *; }
--dontpreverify
--dontoptimize
--dontshrink
--dontwarn **
--dontnote **