Feature: allow queue callback function parameter

README.md

@@ -78,6 +78,12 @@ archive.directory('subdir/', false);
 // append files from a glob pattern
 archive.glob('file*.txt', {cwd:__dirname});
 
+// append a file with a callback for when the queue has been processed.
+// usefull for implementing backpressure prevention mechanisms
+archive.file("file1.txt", { name: "file4.txt" }, () => {
+  console.log("task complete, do something....");
+});
+
 // finalize the archive (ie we are done appending files but streams have to finish yet)
 // 'close', 'end' or 'finish' may be fired right after calling this method so register to them beforehand
 archive.finalize();

lib/core.js

@@ -553,9 +553,10 @@ Archiver.prototype.abort = function() {
  * @fires  Archiver#entry
  * @param  {(Buffer|Stream|String)} source The input source.
  * @param  {EntryData} data See also {@link ZipEntryData} and {@link TarEntryData}.
+ * @param  {Function} callback 
  * @return {this}
  */
-Archiver.prototype.append = function(source, data) {
+Archiver.prototype.append = function(source, data, cb = () => {}) {
   if (this._state.finalize || this._state.aborted) {
     this.emit('error', new ArchiverError('QUEUECLOSED'));
     return this;
@@ -588,7 +589,7 @@ Archiver.prototype.append = function(source, data) {
   this._queue.push({
     data: data,
     source: source
-  });
+  }, cb);
 
   return this;
 };

package.json

@@ -31,6 +31,7 @@
     "archiver-utils": "^2.1.0",
     "async": "^3.2.0",
     "buffer-crc32": "^0.2.1",
+    "chai-spies": "^1.0.0",
     "readable-stream": "^3.6.0",
     "readdir-glob": "^1.0.0",
     "tar-stream": "^2.2.0",

test/archiver.js

@@ -3,9 +3,13 @@ var fs = require('fs');
 var PassThrough = require('readable-stream').PassThrough;
 var WriteStream = fs.createWriteStream;
 
-var assert = require('chai').assert;
+var spies = require('chai-spies');
+var chai = require('chai')
+var assert = chai.assert;
 var mkdir = require('mkdirp');
 
+chai.use(spies);
+
 var helpers = require('./helpers');
 var HashStream = helpers.HashStream;
 var UnBufferedStream = helpers.UnBufferedStream;
@@ -352,6 +356,28 @@ describe('archiver', function() {
       });
     });
 
+    describe('#callback function', function() {
+      var archive;
+
+      it('should call callback function', function(done) {
+        archive = archiver('json');
+        var testStream = new WriteStream('tmp/promise.json');
+
+        const noop = () => {}
+        const spy = chai.spy(noop);
+
+        archive.pipe(testStream);
+
+        archive
+          .append(testBuffer, { name: 'buffer.txt', date: testDate }, spy)
+          .finalize()
+          .then(function() {
+            chai.expect(spy).to.have.been.called();
+            done()
+          })
+      });
+    });
+
     describe('#errors', function() {
         var archive;