arch: split ':common:android' from ':common'

In preparation for moving libanki to be pure JVM, we need :common to be
a java-library.

JSON is supported by both android and JVM (with slightly differing apis
so it can remain in `:common`

Assisted-by: Claude Opus 4.6

Related to https://redirect.github.com/ankidroid/Anki-Android-Backend/issues/674

Author: david-allison

AnkiDroid/build.gradle

@@ -385,6 +385,7 @@ dependencies {
 
     // modules
     implementation project(":common")
+    implementation project(":common:android")
     implementation project(":compat")
     implementation project(":libanki")
     implementation project(":vbpd")

AnkiDroid/jacoco.gradle

@@ -126,8 +126,10 @@ tasks.register('jacocoTestReport', JacocoReport) {
     dependsOn("connectedPlay${rootProject.androidTestVariantName}AndroidTest")
 }
 
-// modules do not yet support flavors (play/full)
-def modulesToUnitTest = [":common", ":libanki", ":compat"]
+// Android library modules (do not yet support flavors play/full)
+def androidModulesToUnitTest = [":libanki", ":compat"]
+// JVM modules: use 'test' task and 'classes/kotlin/main' class dir
+def jvmModulesToUnitTest = [":common"]
 
 // A unit-test only report task
 tasks.register('jacocoUnitTestReport', JacocoReport) {report ->
@@ -145,10 +147,15 @@ tasks.register('jacocoUnitTestReport', JacocoReport) {report ->
     includeUnitTestCoverage(report, getProject(), flavorClassDir)
     dependsOn('testPlayDebugUnitTest')
 
-    for (module in modulesToUnitTest) {
+    for (module in androidModulesToUnitTest) {
         includeUnitTestCoverage(report, project(module), moduleClassDir)
         dependsOn("${module}:testDebugUnitTest")
     }
+
+    for (module in jvmModulesToUnitTest) {
+        includeUnitTestCoverage(report, project(module), 'classes/kotlin/main')
+        dependsOn("${module}:test")
+    }
 }
 
 gradle.projectsEvaluated {
@@ -159,12 +166,18 @@ gradle.projectsEvaluated {
             task.outputs.cacheIf { false }
         }
     }
-    for (module in modulesToUnitTest) {
+    for (module in androidModulesToUnitTest) {
         project(module).tasks.named('testDebugUnitTest')?.configure {task ->
             task.outputs.upToDateWhen { false }
             task.outputs.cacheIf { false }
         }
     }
+    for (module in jvmModulesToUnitTest) {
+        project(module).tasks.named('test')?.configure {task ->
+            task.outputs.upToDateWhen { false }
+            task.outputs.cacheIf { false }
+        }
+    }
 }
 
 

build.gradle.kts

@@ -116,7 +116,7 @@ subprojects {
                     compilerArgs += "-XXLanguage:+ExplicitBackingFields"
                 }
 
-                if (project.path !in listOf(":api", ":common")) {
+                if (project.path !in listOf(":api", ":common", ":common:android")) {
                     compilerArgs += "-opt-in=kotlinx.coroutines.ExperimentalCoroutinesApi"
                 }
                 if (project.path != ":api") {

common/README.md

@@ -1,11 +1,10 @@
 ## AnkiDroid Common
 
-AnkiDroid Common is a [Gradle module](https://developer.android.com/topic/modularization) 
+AnkiDroid Common is a pure JVM [Gradle module](https://developer.android.com/topic/modularization) 
 containing utility functions, and definitions for core functionality used by other modules 
 within AnkiDroid. Common should be the base of the AnkiDroid dependency tree.
 
-Common is used by `libAnki` (which has no Android dependencies), so dependencies on the Android 
-framework should be in packages named `android`.
+Common has no Android dependencies. Code requiring Android APIs belongs in `:common:android`.
 
 This module is expected to define interfaces which are initialized in the `AnkiDroid` module
 
@@ -19,48 +18,29 @@ These are to be initialized higher up the dependency tree, typically in `AnkiDro
 
 ### `com.ichi2.anki.common.utils`
 
-Utility classes and methods without an Android dependency
-
+Utility classes and methods
 
 ### `com.ichi2.anki.common.utils.ext` 
 
 Extension methods, universally applicable to the classes they extend
 
-Examples:
-
-* `Int.kt` - `ifNotZero`
-* `InputStream.kt` - `convertToString`
-
-### `com.ichi2.anki.common.utils.android` 
-
-Utilities with a dependency on Android
-
 ## Context
 
-This is a work in progress. As discussed in 
+As discussed in 
 [#12582](https://github.com/ankidroid/Anki-Android/issues/12582), AnkiDroid decided to split the 
 codebase into two modules, `libAnki` (business logic) and `AnkiDroid` (code interacting with 
-Android APIs). 
-
-At the time of writing, this split is not yet done. We expect to do it with the following steps:
+Android APIs). `common` existed for logic which both `AnkiDroid` and `libAnki` depended on.  
 
-* `com.ichi2.compat` was deemed to be an easy module to split out to trial this refactor 
- but this had circular dependencies
-* A `common` module was proposed to fix this
-* To reduce the execution time of tests, `libAnki` should have no dependencies on Android 
-  * A lint rule will be applied to `libAnki` from using Android dependencies
-  * The alternate: splitting modules based on architecture was deemed to be unwieldy 
+Later,  `compat` was split out, also depending on `common`, solidifying `common`  
 
-The following were blockers for `compat` to be split out
+[Backend - #647](https://github.com/ankidroid/Anki-Android-Backend/issues/674): `libAnki` is 
+intended to be converted to a `java-library`, so `:common` was split into `:common:android`, 
+ensuring that
 
-* `isRobolectric`
-* `CrashReportService`
-* `showThemedToast`
-* `TimeManager` (maybe)
-* `@KotlinCleanup` (maybe)
 
 Discussed on Discord: https://discord.gg/qjzcRTx
 
 * Discussion: https://discord.com/channels/368267295601983490/701922522836369498/1243991110888591482
 * Thread: https://discord.com/channels/368267295601983490/1244372448233914438
 * https://github.com/ankidroid/Anki-Android/pull/16498
+* [#20547 - extract `:compat`](https://github.com/ankidroid/Anki-Android/issues/20547)

common/android/README.md

@@ -0,0 +1,19 @@
+## AnkiDroid Common (Android)
+
+Android-specific utilities which are generally applicable to AnkiDroid.
+
+Split from `:common` to ensure that `:common` is a `java-library`, to support fast, pure-JVM tests.
+
+## Packages
+
+### `com.ichi2.anki.common.utils.android`
+
+Android-specific utilities (e.g. `isRobolectric`)
+
+### `com.ichi2.anki.common.utils.ext`
+
+Extension methods on Android framework classes (e.g. `Intent`)
+
+### `com.ichi2.anki.utils.android`
+
+Color manipulation utilities (`darkenColor`, `lightenColorAbsolute`)

common/android/build.gradle.kts

@@ -0,0 +1,63 @@
+/*
+ *  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/>.
+ */
+
+import com.android.build.api.dsl.LibraryExtension
+
+plugins {
+    alias(libs.plugins.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"))
+
+    implementation(libs.androidx.annotation)
+    implementation(libs.jakewharton.timber)
+}

common/android/src/main/AndroidManifest.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest>
+
+</manifest>