Attach event listener to clone only for Stream #995

docs/changelog.md

@@ -26,6 +26,10 @@ Requires libvips v8.6.0.
   [#977](https://github.com/lovell/sharp/pull/977)
   [@jardakotesovec](https://github.com/jardakotesovec)
 
+* Attach finish event listener to a clone only for Stream-based input.
+  [#995](https://github.com/lovell/sharp/issues/995)
+  [@whmountains](https://github.com/whmountains)
+
 * Add tilecache before smartcrop to avoid over-computation of previous operations.
   [#1028](https://github.com/lovell/sharp/issues/1028)
   [@coffeebite](https://github.com/coffeebite)

lib/input.js

@@ -155,12 +155,14 @@ function clone () {
   const clone = this.constructor.call();
   clone.options = Object.assign({}, this.options);
   // Pass 'finish' event to clone for Stream-based input
-  this.on('finish', function () {
-    // Clone inherits input data
-    that._flattenBufferIn();
-    clone.options.bufferIn = that.options.bufferIn;
-    clone.emit('finish');
-  });
+  if (this._isStreamInput()) {
+    this.on('finish', function () {
+      // Clone inherits input data
+      that._flattenBufferIn();
+      clone.options.bufferIn = that.options.bufferIn;
+      clone.emit('finish');
+    });
+  }
   return clone;
 }
 

test/unit/clone.js

@@ -60,4 +60,18 @@ describe('Clone', function () {
     // Go
     fs.createReadStream(fixtures.inputJpg).pipe(rotator);
   });
+
+  it('Stream-based input attaches finish event listener to original', function () {
+    const original = sharp();
+    const clone = original.clone();
+    assert.strictEqual(1, original.listenerCount('finish'));
+    assert.strictEqual(0, clone.listenerCount('finish'));
+  });
+
+  it('Non Stream-based input does not attach finish event listeners', function () {
+    const original = sharp(fixtures.inputJpg);
+    const clone = original.clone();
+    assert.strictEqual(0, original.listenerCount('finish'));
+    assert.strictEqual(0, clone.listenerCount('finish'));
+  });
 });