feat: support custom compileSdk setting (#1431)

* feat: support custom compileSdk setting
* chore: apply suggestions from code review
* chore: apply cdv-gradle-config-defaults.json suggestion
* fix: set compile sdk when null
* fix: move compileSdk null check to gradle
* fix: compile sdk requirement warning & display in gradle per subproject

Co-authored-by: Norman Breau <norman@nbsolutions.ca>

lib/check_reqs.js

@@ -44,6 +44,31 @@ module.exports.get_target = function (projectRoot) {
     return `android-${Math.max(userTargetSdkVersion, SDK_VERSION)}`;
 };
 
+/**
+ * @param {string} projectRoot
+ * @returns {string} The android target in format "android-${target}"
+ */
+module.exports.get_compile = function (projectRoot) {
+    const userTargetSdkVersion = getUserTargetSdkVersion(projectRoot) || SDK_VERSION;
+    const userCompileSdkVersion = getUserCompileSdkVersion(projectRoot) || userTargetSdkVersion;
+
+    module.exports.isCompileSdkValid(userCompileSdkVersion, userTargetSdkVersion);
+
+    return userCompileSdkVersion;
+};
+
+module.exports.isCompileSdkValid = (compileSdk, targetSdk) => {
+    targetSdk = (targetSdk || SDK_VERSION);
+    compileSdk = (compileSdk || targetSdk);
+    const isValid = compileSdk >= targetSdk;
+
+    if (!isValid) {
+        events.emit('warn', `The "android-compileSdkVersion" (${compileSdk}) should be greater than or equal to the "android-targetSdkVersion" (${targetSdk}).`);
+    }
+
+    return isValid;
+};
+
 /**
  * @param {string} projectRoot
  * @returns {number} target sdk or 0 if undefined
@@ -61,6 +86,23 @@ function getUserTargetSdkVersion (projectRoot) {
     return isNaN(targetSdkVersion) ? 0 : targetSdkVersion;
 }
 
+/**
+ * @param {string} projectRoot
+ * @returns {number} target sdk or 0 if undefined
+ */
+function getUserCompileSdkVersion (projectRoot) {
+    // If the repo config.xml file exists, find the desired compileSdkVersion.
+    // We need to use the cordova project's config.xml here, since the platform
+    // project's config.xml does not yet have the user's preferences when this
+    // function is called during `Api.createPlatform`.
+    const configFile = path.join(projectRoot, '../../config.xml');
+    if (!fs.existsSync(configFile)) return 0;
+
+    const configParser = new ConfigParser(configFile);
+    const compileSdkVersion = parseInt(configParser.getPreference('android-compileSdkVersion', 'android'), 10);
+    return isNaN(compileSdkVersion) ? 0 : compileSdkVersion;
+}
+
 module.exports.get_gradle_wrapper = function () {
     let androidStudioPath;
     let i = 0;