Allow hooks to provide implementation for decorated methods

Whenever a before-hook returns a function it will be used instead of the original method.
When executing such a substitute function it receives a pointer to the original one as well as all its arguments.

Author: rosen-vladimirov

helpers.ts

@@ -281,14 +281,32 @@ export function appendZeroesToVersion(version: string, requiredVersionLength: nu
 	return version;
 }
 
-export function decorateMethod(before: (method1: any, self1: any, args1: any[]) => Promise<void>, after: (method2: any, self2: any, result2: any, args2: any[]) => Promise<any>) {
+export function decorateMethod(before: (method1: any, self1: any, args1: any[]) => Promise<any>, after: (method2: any, self2: any, result2: any, args2: any[]) => Promise<any>) {
 	return (target: Object, propertyKey: string, descriptor: TypedPropertyDescriptor<Function>) => {
 		const sink = descriptor.value;
 		descriptor.value = async function (...args: any[]): Promise<any> {
+			let newMethods: Function[] = null;
 			if (before) {
-				await before(sink, this, args);
+				newMethods = await before(sink, this, args);
 			}
-			const result = sink.apply(this, args);
+
+			let hasBeenReplaced = false;
+			let result: any;
+			if (newMethods && newMethods.length) {
+				// Find all functions
+				_(newMethods)
+					.filter(f => _.isFunction(f))
+					.each(f => {
+						// maybe add logger.trace here
+						hasBeenReplaced = true;
+						result = f(args, sink.bind(this));
+					});
+			}
+
+			if (!hasBeenReplaced) {
+				result = sink.apply(this, args);
+			}
+
 			if (after) {
 				return await after(sink, this, result, args);
 			}
@@ -327,7 +345,7 @@ export function hook(commandName: string) {
 	return decorateMethod(
 		async (method: any, self: any, args: any[]) => {
 			const hooksService = getHooksService(self);
-			await hooksService.executeBeforeHooks(commandName, prepareArguments(method, args, hooksService));
+			return hooksService.executeBeforeHooks(commandName, prepareArguments(method, args, hooksService));
 		},
 		async (method: any, self: any, resultPromise: any, args: any[]) => {
 			const result = await resultPromise;

services/hooks-service.ts

@@ -63,7 +63,7 @@ export class HooksService implements IHooksService {
 		return this.executeHooks(afterHookName, traceMessage, hookArguments);
 	}
 
-	private async executeHooks(hookName: string, traceMessage: string, hookArguments?: IDictionary<any>): Promise<void> {
+	private async executeHooks(hookName: string, traceMessage: string, hookArguments?: IDictionary<any>): Promise<any> {
 		if (this.$config.DISABLE_HOOKS || !this.$options.hooks) {
 			return;
 		}
@@ -75,19 +75,22 @@ export class HooksService implements IHooksService {
 		this.initialize(projectDir);
 
 		this.$logger.trace(traceMessage);
-
+		const results: any[] = [];
 		try {
 			for (const hooksDirectory of this.hooksDirectories) {
-				await this.executeHooksInDirectory(hooksDirectory, hookName, hookArguments);
+				results.push(await this.executeHooksInDirectory(hooksDirectory, hookName, hookArguments));
 			}
 		} catch (err) {
 			this.$logger.trace("Failed during hook execution.");
 			this.$errors.failWithoutHelp(err.message || err);
 		}
+
+		return _.flatten(results);
 	}
 
-	private async executeHooksInDirectory(directoryPath: string, hookName: string, hookArguments?: IDictionary<any>): Promise<void> {
+	private async executeHooksInDirectory(directoryPath: string, hookName: string, hookArguments?: IDictionary<any>): Promise<any[]> {
 		hookArguments = hookArguments || {};
+		const results: any[] = [];
 		const hooks = this.getHooksByName(directoryPath, hookName);
 		for (let i = 0; i < hooks.length; ++i) {
 			const hook = hooks[i];
@@ -129,7 +132,8 @@ export class HooksService implements IHooksService {
 				if (maybePromise) {
 					this.$logger.trace('Hook promises to signal completion');
 					try {
-						await maybePromise;
+						const result = await maybePromise;
+						results.push(result);
 					} catch (err) {
 						if (err && _.isBoolean(err.stopExecution) && err.errorAsWarning === true) {
 							this.$logger.warn(err.message || err);
@@ -144,12 +148,16 @@ export class HooksService implements IHooksService {
 					this.$logger.trace("Executing %s hook at location %s with environment ", hookName, hook.fullPath, environment);
 
 					const output = await this.$childProcess.spawnFromEvent(command, [hook.fullPath], "close", environment, { throwError: false });
+					results.push(output);
+
 					if (output.exitCode !== 0) {
 						throw new Error(output.stdout + output.stderr);
 					}
 				}
 			}
 		}
+
+		return results;
 	}
 
 	private getHooksByName(directoryPath: string, hookName: string): IHook[] {