refactor: introduce shouldprepare hook

lib/definitions/platform.d.ts

@@ -78,6 +78,13 @@ interface IPlatformService extends NodeJS.EventEmitter {
 	 */
 	shouldInstall(device: Mobile.IDevice, projectData: IProjectData, outputPath?: string): Promise<boolean>;
 
+	/**
+	 * Determines whether the project should undergo the prepare process.
+	 * @param {IShouldPrepareInfo} shouldPrepareInfo Options needed to decide whether to prepare.
+	 * @returns {Promise<boolean>} true indicates that the project should be prepared.
+	 */
+	shouldPrepare(shouldPrepareInfo: IShouldPrepareInfo): Promise<boolean>
+
 	/**
 	 * Installs the application on specified device.
 	 * When finishes, saves .nsbuildinfo in application root folder to indicate the prepare that was used to build the app.
@@ -314,11 +321,18 @@ interface IPreparePlatformJSInfo extends IPreparePlatformCoreInfo, ICopyAppFiles
 	projectFilesConfig?: IProjectFilesConfig;
 }
 
-interface IPreparePlatformCoreInfo extends IPreparePlatformInfoBase {
-	platformSpecificData: IPlatformSpecificData
+interface IShouldPrepareInfo extends IOptionalProjectChangesInfoComposition {
+	platformInfo: IPreparePlatformInfo;
+}
+
+interface IOptionalProjectChangesInfoComposition {
 	changesInfo?: IProjectChangesInfo;
 }
 
+interface IPreparePlatformCoreInfo extends IPreparePlatformInfoBase, IOptionalProjectChangesInfoComposition {
+	platformSpecificData: IPlatformSpecificData
+}
+
 interface IPreparePlatformInfo extends IPreparePlatformInfoBase, IPlatformConfig, IPlatformTemplate, ISkipNativeCheckOptional { }
 
 interface IPlatformConfig {

lib/services/platform-service.ts

@@ -187,13 +187,25 @@ export class PlatformService extends EventEmitter implements IPlatformService {
 		return _.filter(this.$platformsData.platformsNames, p => { return this.isPlatformPrepared(p, projectData); });
 	}
 
-	public async preparePlatform(platformInfo: IPreparePlatformInfo): Promise<boolean> {
+	@helpers.hook('shouldPrepare')
+	public async shouldPrepare(shouldPrepareInfo: IShouldPrepareInfo): Promise<boolean> {
+		shouldPrepareInfo.changesInfo = shouldPrepareInfo.changesInfo || await this.getChangesInfo(shouldPrepareInfo.platformInfo);
+		const requiresNativePrepare = (!shouldPrepareInfo.platformInfo.nativePrepare || !shouldPrepareInfo.platformInfo.nativePrepare.skipNativePrepare) && shouldPrepareInfo.changesInfo.nativePlatformStatus === constants.NativePlatformStatus.requiresPrepare;
+
+		return shouldPrepareInfo.changesInfo.hasChanges || requiresNativePrepare;
+	}
+
+	private async getChangesInfo(platformInfo: IPreparePlatformInfo): Promise<IProjectChangesInfo> {
 		const platformData = this.$platformsData.getPlatformData(platformInfo.platform, platformInfo.projectData);
 
-		const changesInfo = await this.initialPrepare(platformInfo.platform, platformData, platformInfo.appFilesUpdaterOptions, platformInfo.platformTemplate, platformInfo.projectData, platformInfo.config, platformInfo.nativePrepare, platformInfo);
-		const requiresNativePrepare = (!platformInfo.nativePrepare || !platformInfo.nativePrepare.skipNativePrepare) && changesInfo.nativePlatformStatus === constants.NativePlatformStatus.requiresPrepare;
+		return this.initialPrepare(platformInfo.platform, platformData, platformInfo.appFilesUpdaterOptions, platformInfo.platformTemplate, platformInfo.projectData, platformInfo.config, platformInfo.nativePrepare, platformInfo);
+	}
+
+	public async preparePlatform(platformInfo: IPreparePlatformInfo): Promise<boolean> {
+		const changesInfo = await this.getChangesInfo(platformInfo);
+		const shouldPrepare = await this.shouldPrepare({ platformInfo, changesInfo });
 
-		if (changesInfo.hasChanges || requiresNativePrepare) {
+		if (shouldPrepare) {
 			// Always clear up the app directory in platforms if `--bundle` value has changed in between builds or is passed in general
 			// this is done as user has full control over what goes in platforms when `--bundle` is passed
 			// and we may end up with duplicate symbols which would fail the build

test/stubs.ts

@@ -613,6 +613,9 @@ export class CommandsService implements ICommandsService {
 }
 
 export class PlatformServiceStub extends EventEmitter implements IPlatformService {
+	public shouldPrepare(): Promise<boolean> {
+		return Promise.resolve(true);
+	}
 
 	public validateOptions(): Promise<boolean> {
 		return Promise.resolve(true);