Always use the NDK version from source.properties.

Previously, `RustAndroidPlugin` would read the
NDK version from `source.properties` in the NDK
path, while `CargoBuildTask` would try to infer
the NDK version from the pathname.

Inferring the NDK version from the pathname would
fail if the pathname didn't contain the version
(e.g., Mach currently installs the NDK used to
build Firefox for Android into
`~/.mozbuild/android-ndk-r26c`), causing
`Toolchain` to return the wrong path to `ar` for
new NDK versions.

Author: linabutler

plugin/src/main/kotlin/com/nishtahir/CargoBuildTask.kt

@@ -15,6 +15,9 @@ open class CargoBuildTask : DefaultTask() {
     @Input
     var toolchain: Toolchain? = null
 
+    @Input
+    var ndk: Ndk? = null
+
     @Suppress("unused")
     @TaskAction
     fun build() = with(project) {
@@ -25,10 +28,12 @@ open class CargoBuildTask : DefaultTask() {
                 throw GradleException("toolchain cannot be null")
             }
 
+            val ndk = ndk ?: throw GradleException("ndk cannot be null")
+
             project.plugins.all {
                 when (it) {
-                    is AppPlugin -> buildProjectForTarget<AppExtension>(project, toolchain, this)
-                    is LibraryPlugin -> buildProjectForTarget<LibraryExtension>(project, toolchain, this)
+                    is AppPlugin -> buildProjectForTarget<AppExtension>(project, toolchain, ndk, this)
+                    is LibraryPlugin -> buildProjectForTarget<LibraryExtension>(project, toolchain, ndk, this)
                 }
             }
             // CARGO_TARGET_DIR can be used to force the use of a global, shared target directory
@@ -77,8 +82,7 @@ open class CargoBuildTask : DefaultTask() {
         }
     }
 
-    inline fun <reified T : BaseExtension> buildProjectForTarget(project: Project, toolchain: Toolchain, cargoExtension: CargoExtension) {
-        val app = project.extensions[T::class]
+    inline fun <reified T : BaseExtension> buildProjectForTarget(project: Project, toolchain: Toolchain, ndk: Ndk, cargoExtension: CargoExtension) {
         val apiLevel = cargoExtension.apiLevels[toolchain.platform]!!
         val defaultTargetTriple = getDefaultTargetTriple(project, cargoExtension.rustcCommand)
 
@@ -165,13 +169,8 @@ open class CargoBuildTask : DefaultTask() {
 
                 // Cross-compiling to Android requires toolchain massaging.
                 if (toolchain.type != ToolchainType.DESKTOP) {
-                    val ndkPath = app.ndkDirectory
-                    val ndkVersion = ndkPath.name
-                    val ndkVersionMajor = try {
-                        ndkVersion.split(".").first().toInt()
-                    } catch (ex: NumberFormatException) {
-                        0 // Falls back to generic behaviour.
-                    }
+                    val ndkPath = ndk.path
+                    val ndkVersionMajor = ndk.versionMajor
 
                     val toolchainDirectory = if (toolchain.type == ToolchainType.ANDROID_PREBUILT) {
                         environment("CARGO_NDK_MAJOR_VERSION", ndkVersionMajor)

plugin/src/main/kotlin/com/nishtahir/RustAndroidPlugin.kt

@@ -107,6 +107,11 @@ val toolchains = listOf(
                 "android/x86_64")
 )
 
+data class Ndk(val path: File, val version: String) {
+    val versionMajor: Int
+        get() = version.split(".").first().toInt()
+}
+
 data class Toolchain(val platform: String,
                      val type: ToolchainType,
                      val target: String,
@@ -227,21 +232,23 @@ open class RustAndroidPlugin : Plugin<Project> {
         }
 
         // Determine the NDK version, if present
-        val ndkSourceProperties = Properties()
-        val ndkSourcePropertiesFile = File(extensions[T::class].ndkDirectory, "source.properties")
-        if (ndkSourcePropertiesFile.exists()) {
-            ndkSourceProperties.load(ndkSourcePropertiesFile.inputStream())
+        val ndk = extensions[T::class].ndkDirectory.let {
+            val ndkSourceProperties = Properties()
+            val ndkSourcePropertiesFile = File(it, "source.properties")
+            if (ndkSourcePropertiesFile.exists()) {
+                ndkSourceProperties.load(ndkSourcePropertiesFile.inputStream())
+            }
+            val ndkVersion = ndkSourceProperties.getProperty("Pkg.Revision", "0.0")
+            Ndk(path = it, version = ndkVersion)
         }
-        val ndkVersion = ndkSourceProperties.getProperty("Pkg.Revision", "0.0")
-        val ndkVersionMajor = ndkVersion.split(".").first().toInt()
 
         // Determine whether to use prebuilt or generated toolchains
         val usePrebuilt =
             cargoExtension.localProperties.getProperty("rust.prebuiltToolchains")?.equals("true") ?:
             cargoExtension.prebuiltToolchains ?:
-            (ndkVersionMajor >= 19);
+            (ndk.versionMajor >= 19);
 
-        if (usePrebuilt && ndkVersionMajor < 19) {
+        if (usePrebuilt && ndk.versionMajor < 19) {
             throw GradleException("usePrebuilt = true requires NDK version 19+")
         }
 
@@ -299,6 +306,7 @@ open class RustAndroidPlugin : Plugin<Project> {
                 group = RUST_TASK_GROUP
                 description = "Build library ($target)"
                 toolchain = theToolchain
+                this.ndk = ndk
             }
 
             if (!usePrebuilt) {