fix(WorkerPool): trace stacks to avoid duplicated err.messages from workers (#13)

Author: sendilkumarn

src/WorkerError.js

@@ -0,0 +1,31 @@
+const stack = (err, worker, workerId) => {
+  const originError = err.stack
+    .split('\n')
+    .filter(line => line.trim().startsWith('at'));
+
+  const workerError = worker
+    .split('\n')
+    .filter(line => line.trim().startsWith('at'));
+
+  const diff = workerError.slice(0, workerError.length - originError.length).join('\n');
+
+  originError.unshift(diff);
+  originError.unshift(err.message);
+  originError.unshift(`Thread Loader (Worker ${workerId})`);
+
+  return originError.join('\n');
+};
+
+class WorkerError extends Error {
+  constructor(err, workerId) {
+    super(err);
+    this.name = err.name;
+    this.message = err.message;
+
+    Error.captureStackTrace(this, this.constructor);
+
+    this.stack = stack(err, this.stack, workerId);
+  }
+}
+
+export default WorkerError;

src/WorkerPool.js

@@ -4,6 +4,7 @@ import childProcess from 'child_process';
 import asyncQueue from 'async/queue';
 import asyncMapSeries from 'async/mapSeries';
 import readBuffer from './readBuffer';
+import WorkerError from './WorkerError';
 
 const workerPath = require.resolve('./worker');
 
@@ -183,14 +184,7 @@ class PoolWorker {
     } else {
       obj = arg;
     }
-    const err = new Error(obj.message);
-    err.message = obj.message;
-    if (obj.stack) {
-      err.stack = `${obj.stack}\n\tfrom thread-loader (worker ${this.id})\n${err.stack}`;
-    }
-    err.hideStack = obj.hideStack;
-    err.details = obj.details;
-    return err;
+    return new WorkerError(obj, this.id);
   }
 
   readBuffer(length, callback) {
@@ -272,4 +266,3 @@ export default class WorkerPool {
     }
   }
 }
-