fix: do not consume maxCount for files skipped by fileFilter

index.js

@@ -41,8 +41,13 @@ Multer.prototype._makeMiddleware = function (fields, fileStrategy) {
         return cb(new MulterError('LIMIT_UNEXPECTED_FILE', file.fieldname))
       }
 
-      filesLeft[file.fieldname] -= 1
-      fileFilter(req, file, cb)
+      // Only count the file against the field's maxCount once the user's
+      // fileFilter has accepted it. A file skipped via cb(null, false) is
+      // never stored, so it must not consume a slot (see #1419).
+      fileFilter(req, file, function (err, includeFile) {
+        if (!err && includeFile) filesLeft[file.fieldname] -= 1
+        cb(err, includeFile)
+      })
     }
 
     return {

test/file-filter.js

@@ -18,6 +18,10 @@ function reportFakeError (req, file, cb) {
   cb(new Error('Fake error'))
 }
 
+function skipByOriginalName (req, file, cb) {
+  cb(null, file.originalname !== 'tiny0.dat')
+}
+
 describe('File Filter', function () {
   it('should skip some files', function (done) {
     var form = new FormData()
@@ -41,6 +45,24 @@ describe('File Filter', function () {
     })
   })
 
+  it('should not consume maxCount for files skipped by fileFilter (#1419)', function (done) {
+    var form = new FormData()
+    var upload = withFilter(skipByOriginalName)
+    var parser = upload.array('docs', 1)
+
+    // Two files on the same field: the first is skipped by the filter, the
+    // second accepted. The skipped file must not consume the single slot.
+    form.append('docs', util.file('tiny0.dat'))
+    form.append('docs', util.file('tiny1.dat'))
+
+    util.submitForm(parser, form, function (err, req) {
+      assert.ifError(err)
+      assert.strictEqual(req.files.length, 1)
+      assert.strictEqual(req.files[0].originalname, 'tiny1.dat')
+      done()
+    })
+  })
+
   it('should report errors from fileFilter', function (done) {
     var form = new FormData()
     var upload = withFilter(reportFakeError)