Kill sass compiler when LiveSync stops

In a long living process (like in NativeScript Sidekick), the LiveSync process for a project may be stopped, but this will not stop the `node-sass` running in the background.
Use the after-watch hook, which is raised when LiveSync operation stops and kill currently running node-sass compiler. This way we'll not keep running watchers in the background.

Author: rosen-vladimirov

lib/after-watch.js

@@ -0,0 +1,9 @@
+var converter = require('./converter');
+
+module.exports = function ($logger) {
+	var sass = converter.getSassProcess();
+	if (sass) {
+		$logger.info("Stopping sass watch");
+		sass.kill("SIGINT")
+	}
+}

lib/converter.js

@@ -1,8 +1,10 @@
 exports.convert = convert;
+exports.getSassProcess = getSassProcess;
 
 var spawn = require('child_process').spawn;
 var fs = require('fs');
 var path = require('path');
+var currentSassProcess = null;
 
 function convert(logger, projectDir, options) {
     return new Promise(function (resolve, reject) {
@@ -12,7 +14,7 @@ function convert(logger, projectDir, options) {
         var sassPath = path.join(peerSassPath, 'bin/node-sass');
         var appDir = path.join(projectDir, "app");
         var importerPath = path.join(__dirname, "importer.js");
-        
+
         if (fs.existsSync(sassPath)) {
             try {
                 logger.info('Found peer node-sass');
@@ -34,16 +36,16 @@ function convert(logger, projectDir, options) {
         }
 
         logger.trace(process.execPath, nodeArgs.join(' '));
-        var sass = spawn(process.execPath, nodeArgs);
+        currentSassProcess = spawn(process.execPath, nodeArgs);
 
         var isResolved = false;
         var watchResolveTimeout;
-        sass.stdout.on('data', function (data) {
+        currentSassProcess.stdout.on('data', function (data) {
             var stringData = data.toString();
             logger.info(stringData);
         });
 
-        sass.stderr.on('data', function (err) {
+        currentSassProcess.stderr.on('data', function (err) {
             var message = '';
             var stringData = err.toString();
 
@@ -58,7 +60,7 @@ function convert(logger, projectDir, options) {
             logger.info(message);
         });
 
-        sass.on('error', function (err) {
+        currentSassProcess.on('error', function (err) {
             logger.info(err.message);
             if (!isResolved) {
                 isResolved = true;
@@ -67,7 +69,8 @@ function convert(logger, projectDir, options) {
         });
 
         // TODO: Consider using close event instead of exit
-        sass.on('exit', function (code, signal) {
+        currentSassProcess.on('exit', function (code, signal) {
+            currentSassProcess = null;
             if (!isResolved) {
                 isResolved = true;
                 if (code === 0) {
@@ -78,10 +81,14 @@ function convert(logger, projectDir, options) {
             }
         });
 
-        // SASS does not recompile on watch, so directly resolve.        
+        // SASS does not recompile on watch, so directly resolve.
         if (options.watch && !isResolved) {
             isResolved = true;
             resolve();
         }
     });
 }
+
+function getSassProcess() {
+    return currentSassProcess;
+}

lib/watch.js

@@ -2,4 +2,4 @@ var converter = require('./converter');
 
 module.exports = function (logger, projectData, usbLiveSyncService) {
 	return converter.convert(logger, projectData.projectDir, { watch: true });
-}
+}