From 68a2c9491f2e3d78d6a167c9f02d07b8bf570c26 Mon Sep 17 00:00:00 2001
From: Andreas Lind Petersen <andreas@one.com>
Date: Wed, 28 May 2014 22:57:31 +0200
Subject: [PATCH] Avoid emitting the 'error' event more than once.

---
 lib/PngQuant.js  | 17 +++++++++++------
 test/PngQuant.js | 21 +++++++++++++++++++++
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/lib/PngQuant.js b/lib/PngQuant.js
index 3c55d69..8ef0fb2 100644
--- a/lib/PngQuant.js
+++ b/lib/PngQuant.js
@@ -23,20 +23,18 @@ function PngQuant(pngQuantArgs) {
     this.hasEnded = false;
     this.seenDataOnStdout = false;
 
-    this.pngQuantProcess.on('error', function (err) {
-        this.emit('error', err);
-    }.bind(this));
+    this.pngQuantProcess.on('error', this._reportError.bind(this));
 
     this.pngQuantProcess.stderr.on('data', function (data) {
         if (!this.hasEnded) {
-            this.emit('error', new Error('Saw pngquant output on stderr: ' + data.toString('ascii')));
+            this._reportError(new Error('Saw pngquant output on stderr: ' + data.toString('ascii')));
             this.hasEnded = true;
         }
     }.bind(this));
 
     this.pngQuantProcess.on('exit', function (exitCode) {
         if (exitCode > 0 && !this.hasEnded) {
-            this.emit('error', new Error('The pngquant process exited with a non-zero exit code: ' + exitCode));
+            this._reportError(new Error('The pngquant process exited with a non-zero exit code: ' + exitCode));
             this.hasEnded = true;
         }
     }.bind(this));
@@ -49,7 +47,7 @@ function PngQuant(pngQuantArgs) {
             if (this.seenDataOnStdout) {
                 this.emit('end');
             } else {
-                this.emit('error', new Error('PngQuant: The stdout stream ended without emitting any data'));
+                this._reportError(new Error('PngQuant: The stdout stream ended without emitting any data'));
             }
             this.hasEnded = true;
         }
@@ -58,6 +56,13 @@ function PngQuant(pngQuantArgs) {
 
 util.inherits(PngQuant, Stream);
 
+PngQuant.prototype._reportError = function (err) {
+    if (!this.hasEnded) {
+        this.hasEnded = true;
+        this.emit('error', err);
+    }
+};
+
 PngQuant.prototype.write = function (chunk) {
     this.pngQuantProcess.stdin.write(chunk);
 };
diff --git a/test/PngQuant.js b/test/PngQuant.js
index 24a68b0..a3bf2e3 100644
--- a/test/PngQuant.js
+++ b/test/PngQuant.js
@@ -64,4 +64,25 @@ describe('PngQuant', function () {
 
         pngQuant.end(new Buffer('qwvopeqwovkqvwiejvq', 'utf-8'));
     });
+
+    it('should emit a single error if an invalid command line is specified', function (done) {
+        var pngQuant = new PngQuant(['--blabla']),
+            seenError = false;
+
+        pngQuant.on('error', function (err) {
+            expect(pngQuant.commandLine, 'to match', /pngquant --blabla/);
+            if (seenError) {
+                done(new Error('More than one error event was emitted'));
+            } else {
+                seenError = true;
+                setTimeout(done, 100);
+            }
+        }).on('data', function (chunk) {
+            done(new Error('PngQuant emitted data when an error was expected'));
+        }).on('end', function (chunk) {
+            done(new Error('PngQuant emitted end when an error was expected'));
+        });
+
+        pngQuant.end(new Buffer('qwvopeqwovkqvwiejvq', 'utf-8'));
+    });
 });