Add option to skip building and testing Android libraries (#33)

* Add otpion to skip building and testing Android libraries

Add `skip.android=true` to the local.properties files at the project's root to skip Android builds.

README.md

@@ -84,3 +84,38 @@ You can also specify the temporary directory where the library will be extracted
 ## Usage
 
 Please have a look at unit tests, more samples will be added soon.
+
+## Building
+
+-**secp256k1-kmp** is a [Kotlin Multiplatform](https://kotlinlang.org/docs/multiplatform.html) wrapper for Bitcoin Core's [secp256k1 library](https://github.com/bitcoin-core/secp256k1).
+-
+To build the library you need the following:
+- Window 64 bits, Linux 64 bits, or MacOs 64 Bits
+- OpenJDK11 (we recommend using packages provided by https://adoptopenjdk.net/ but there are other options)
+- (optional) Android SDK
+
+It may work with other Operating Systems and JDKs, but then you're on your own (in particular we don't plan to support 32 bits Operating Systems).
+To build the library and publish compiled artefacts locally (so they can be used by other projects):
+
+```sh
+./gradlew :build
+./gradlew :publishToMavenLocal
+```
+
+To run all tests on all platforms:
+
+```sh
+./gradlew allTests
+```
+
+To run tests on a single platform, for example the JVM:
+
+```sh
+./gradlew jvmTest
+```
+
+If you want to skip building Android artefacts create a `local.properties` file in the project's root directory and add the following line:
+
+```
+skip.android=true
+```

native/build.gradle.kts

@@ -1,6 +1,10 @@
 import org.gradle.internal.os.OperatingSystem
 
-evaluationDependsOn(":jni:android")
+val includeAndroid = System.getProperty("includeAndroid")?.toBoolean() ?: true
+
+if (includeAndroid) {
+    evaluationDependsOn(":jni:android")
+}
 
 val currentOs = OperatingSystem.current()
 val bash = if (currentOs.isWindows) "bash.exe" else "bash"
@@ -39,34 +43,39 @@ val buildSecp256k1Ios by tasks.creating(Exec::class) {
     commandLine(bash, "build-ios.sh")
 }
 
-val buildSecp256k1Android by tasks.creating {
-    group = "build"
-    buildSecp256k1.dependsOn(this)
-}
-fun creatingBuildSecp256k1Android(arch: String) = tasks.creating(Exec::class) {
-    group = "build"
-    buildSecp256k1Android.dependsOn(this)
+if (includeAndroid) {
 
-    inputs.files(projectDir.resolve("build-android.sh"))
-    outputs.dir(projectDir.resolve("build/android/$arch"))
-
-    workingDir = projectDir
-
-    val toolchain = when {
-        currentOs.isLinux -> "linux-x86_64"
-        currentOs.isMacOsX -> "darwin-x86_64"
-        currentOs.isWindows -> "windows-x86_64"
-        else -> error("No Android toolchain defined for this OS: $currentOs")
+    val buildSecp256k1Android by tasks.creating {
+        group = "build"
+        buildSecp256k1.dependsOn(this)
     }
-    environment("TOOLCHAIN", toolchain)
-    environment("ARCH", arch)
-    environment("ANDROID_NDK", (project(":jni:android").extensions["android"] as com.android.build.gradle.LibraryExtension).ndkDirectory)
-    commandLine(bash, "build-android.sh")
+
+    fun creatingBuildSecp256k1Android(arch: String) = tasks.creating(Exec::class) {
+        group = "build"
+        buildSecp256k1Android.dependsOn(this)
+
+        inputs.files(projectDir.resolve("build-android.sh"))
+        outputs.dir(projectDir.resolve("build/android/$arch"))
+
+        workingDir = projectDir
+
+        val toolchain = when {
+            currentOs.isLinux -> "linux-x86_64"
+            currentOs.isMacOsX -> "darwin-x86_64"
+            currentOs.isWindows -> "windows-x86_64"
+            else -> error("No Android toolchain defined for this OS: $currentOs")
+        }
+        environment("TOOLCHAIN", toolchain)
+        environment("ARCH", arch)
+        environment("ANDROID_NDK", (project(":jni:android").extensions["android"] as com.android.build.gradle.LibraryExtension).ndkDirectory)
+        commandLine(bash, "build-android.sh")
+    }
+
+    val buildSecp256k1AndroidX86_64 by creatingBuildSecp256k1Android("x86_64")
+    val buildSecp256k1AndroidX86 by creatingBuildSecp256k1Android("x86")
+    val buildSecp256k1AndroidArm64v8a by creatingBuildSecp256k1Android("arm64-v8a")
+    val buildSecp256k1AndroidArmeabiv7a by creatingBuildSecp256k1Android("armeabi-v7a")
 }
-val buildSecp256k1AndroidX86_64 by creatingBuildSecp256k1Android("x86_64")
-val buildSecp256k1AndroidX86 by creatingBuildSecp256k1Android("x86")
-val buildSecp256k1AndroidArm64v8a by creatingBuildSecp256k1Android("arm64-v8a")
-val buildSecp256k1AndroidArmeabiv7a by creatingBuildSecp256k1Android("armeabi-v7a")
 
 val clean by tasks.creating {
     group = "build"

settings.gradle.kts

@@ -7,10 +7,19 @@ pluginManagement {
 }
 rootProject.name = "secp256k1-kmp"
 
+// We use a property defined in `local.properties` to know whether we should build the android application or not.
+// For example, iOS developers may want to skip that most of the time.
+val skipAndroid = File("$rootDir/local.properties").takeIf { it.exists() }
+    ?.inputStream()?.use { java.util.Properties().apply { load(it) } }
+    ?.run { getProperty("skip.android", "false")?.toBoolean() }
+    ?: false
+
+// Use system properties to inject the property in other gradle build files.
+System.setProperty("includeAndroid", (!skipAndroid).toString())
+
 include(
     ":native",
     ":jni",
-    ":jni:android",
     ":jni:jvm",
     ":jni:jvm:darwin",
     ":jni:jvm:linux",
@@ -18,3 +27,10 @@ include(
     ":jni:jvm:all",
     ":tests"
 )
+
+if (!skipAndroid) {
+    print("building android library")
+    include(":jni:android")
+} else {
+    print("skipping android build")
+}

tests/build.gradle.kts

@@ -1,11 +1,16 @@
+
 plugins {
     kotlin("multiplatform")
-    id("com.android.library")
+    if (System.getProperty("includeAndroid")?.toBoolean() == true) {
+        id("com.android.library")
+    }
 }
 
 kotlin {
     explicitApi()
 
+    val includeAndroid = System.getProperty("includeAndroid")?.toBoolean() ?: true
+
     val commonMain by sourceSets.getting {
         dependencies {
             implementation(rootProject)
@@ -29,17 +34,19 @@ kotlin {
         }
     }
 
-    android {
-        compilations.all {
-            kotlinOptions.jvmTarget = "1.8"
-        }
-        sourceSets["androidMain"].dependencies {
-            implementation(project(":jni:android"))
-        }
-        sourceSets["androidTest"].dependencies {
-            implementation(kotlin("test-junit"))
-            implementation("androidx.test.ext:junit:1.1.2")
-            implementation("androidx.test.espresso:espresso-core:3.3.0")
+    if (includeAndroid) {
+        android {
+            compilations.all {
+                kotlinOptions.jvmTarget = "1.8"
+            }
+            sourceSets["androidMain"].dependencies {
+                implementation(project(":jni:android"))
+            }
+            sourceSets["androidTest"].dependencies {
+                implementation(kotlin("test-junit"))
+                implementation("androidx.test.ext:junit:1.1.2")
+                implementation("androidx.test.espresso:espresso-core:3.3.0")
+            }
         }
     }
 
@@ -48,23 +55,26 @@ kotlin {
     ios()
 }
 
-android {
-    defaultConfig {
-        compileSdkVersion(30)
-        minSdkVersion(21)
-        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
-    }
+val includeAndroid = System.getProperty("includeAndroid")?.toBoolean() ?: true
+if (includeAndroid) {
+    extensions.configure<com.android.build.gradle.LibraryExtension>("android") {
+        defaultConfig {
+            compileSdkVersion(30)
+            minSdkVersion(21)
+            testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        }
 
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_1_8
-        targetCompatibility = JavaVersion.VERSION_1_8
-    }
+        compileOptions {
+            sourceCompatibility = JavaVersion.VERSION_1_8
+            targetCompatibility = JavaVersion.VERSION_1_8
+        }
 
-    sourceSets["main"].manifest.srcFile("src/androidMain/AndroidManifest.xml")
+        sourceSets["main"].manifest.srcFile("src/androidMain/AndroidManifest.xml")
 
-    afterEvaluate {
-        tasks.withType<com.android.build.gradle.tasks.factory.AndroidUnitTest>().all {
-            enabled = false
+        afterEvaluate {
+            tasks.withType<com.android.build.gradle.tasks.factory.AndroidUnitTest>().all {
+                enabled = false
+            }
         }
     }
-}
+}