powerShell optimizatio error handling

lib/util.js

@@ -217,39 +217,55 @@ function getWmic() {
 }
 
 function powerShell(cmd) {
+
+  // helper function
+  function dispose(child) {
+    return new Promise((resolve, reject) => {
+      child.stdin.write('exit' + os.EOL);
+      process.nextTick(() => {
+        child.stdin.end()
+        child.kill();
+        resolve();
+      });
+    })
+  }
+
+  let result = '';
+
   return new Promise((resolve, reject) => {
+
     process.nextTick(() => {
 
-      let result = '';
-      const child = spawn('powershell.exe', ['-NoLogo', '-InputFormat', 'Text', '-NoExit', '-ExecutionPolicy', 'Unrestricted', '-Command', '-'], {
-        stdio: 'pipe'
-      });
-
-      if (child) {
-        child.stdout.on('data', function (data) {
-          result = result + data.toString('utf8');
-        });
-        child.stderr.on('data', function (data) {
-          child.kill();
-          reject(data);
-        });
-        child.on('close', function () {
-          child.kill();
-          resolve(result);
-        });
-        child.on('error', function () {
-          child.kill();
-          resolve(result);
+      try {
+        const child = spawn('powershell.exe', ['-NoLogo', '-InputFormat', 'Text', '-NoExit', '-ExecutionPolicy', 'Unrestricted', '-Command', '-'], {
+          stdio: 'pipe'
         });
 
-        try {
-          child.stdin.write(cmd + '\n');
-          child.stdin.end();
-        } catch (e) {
-          reject(result)
+        if (child && child.pid) {
+          child.stdout.on('data', function (data) {
+            result = result + data.toString('utf8');
+          });
+          child.stderr.on('data', function (data) {
+            dispose(child).then(resolve(result));
+          });
+          child.on('close', function () {
+            dispose(child).then(resolve(result));
+            ;
+          });
+          child.on('error', function () {
+            dispose(child).then(resolve(result));
+          });
+
+          try {
+            child.stdin.write(cmd + os.EOL);
+          } catch (e) {
+            dispose(child).then(resolve(result));
+          }
+        } else {
+          resolve(result);
         }
-      } else {
-        reject(result);
+      } catch (e) {
+        resolve(result);
       }
     });
   });