[changed] NativeProcess converts stderr strings that look like th…

…e output of `Error.prototype.toString()` into actual error instances, preserving all of the underlying information

package.json

@@ -68,8 +68,10 @@
     "babel-preset-stage-2": "^6.22.0",
     "babel-runtime": "^6.22.0",
     "cheerio": "^0.22.0",
+    "clean-stack": "^1.1.1",
     "codemirror": "^5.23.0",
     "docdash": "^0.4.0",
+    "error-stack-parser": "^2.0.0",
     "eslint": "^3.14.1",
     "eslint-plugin-babel": "^4.0.1",
     "eslint-plugin-flowtype": "^2.30.0",

src/NativeProcess.js

@@ -4,6 +4,8 @@ import type {StringOrErrorCallback} from './typedef';
 import {spawn} from 'child_process';
 import noop from 'lodash/noop';
 
+const errorPattern = /([^\s]*Error): (.*)[\s\S]*/;
+
 /**
  * Encapsulates a {@link https://nodejs.org/api/child_process.html#child_process_class_childprocess ChildProcess}
  * instance of a `task`
@@ -46,6 +48,32 @@ export class NativeProcess {
     this.task = task;
   }
 
+  /**
+   * If the `stderr` string matches the return format of `Error.prototype.toString()`, turns it into an actual error
+   * instance, preserving all of the underlying information.
+   *
+   * @memberOf NativeProcess
+   * @static
+   * @private
+   * @method stderrToError
+   * @param {string} stderr - error output
+   * @return {Error} an error instance
+   */
+  static stderrToError(stderr: string): Error {
+    const matched = stderr.match(errorPattern);
+
+    if (!matched) {
+      return new Error(stderr);
+    }
+    const [stack, name, message] = matched,
+      error = new Error(message);
+
+    error.name = name;
+    error.stack = stack;
+
+    return error;
+  }
+
   /**
    * Execute the command
    *
@@ -89,7 +117,7 @@ export class NativeProcess {
     });
     this.proc.on('close', code => {
       this.proc = null;
-      callback(code ? new Error(stderr) : null, stdout);
+      callback(code ? NativeProcess.stderrToError(stderr) : null, stdout);
     });
   }
 

test/NativeProcess.spec.js

@@ -11,7 +11,7 @@ chai.use(sinonChai);
 
 /* eslint-disable no-unused-expressions */
 
-let cmp, callback, on, kill, stdoutOn, stderrOn;
+let cmp, callback, on, kill, stdoutOn, stderrOn, errorResult;
 
 describe('NativeProcess', () => {
 
@@ -24,6 +24,35 @@ describe('NativeProcess', () => {
     expect(cmp.task).equal('script');
   });
 
+  describe('stderrToError plain error message', () => {
+
+    beforeEach(() => {
+      errorResult = NativeProcess.stderrToError('something is wrong');
+    });
+
+    it('returns result', () => {
+      expect(errorResult.name).equal('Error');
+      expect(errorResult.message).equal('something is wrong');
+    });
+
+  });
+
+  describe('stderrToError matches format of `Error.prototype.toString()`', () => {
+
+    beforeEach(() => {
+      errorResult = NativeProcess.stderrToError(`Something unusable SyntaxError: something is wrong again
+    at <anonymous>:1:1`);
+    });
+
+    it('returns result', () => {
+      expect(errorResult.name).equal('SyntaxError');
+      expect(errorResult.message).equal('something is wrong again');
+      expect(errorResult.stack).equal(`SyntaxError: something is wrong again
+    at <anonymous>:1:1`);
+    });
+
+  });
+
   describe('run', () => {
 
     describe('already running', () => {