From 87a2d2452cf855076aef5a5036cac7d545cc446b Mon Sep 17 00:00:00 2001
From: Yomguithereal <guillaumeplique@gmail.com>
Date: Tue, 4 Oct 2022 16:51:40 +0200
Subject: [PATCH] Fixing MultiSet.remove Fix #197

---
 CHANGELOG.md      |  4 ++++
 multi-set.js      | 13 +++++++++----
 test/multi-set.js | 17 +++++++++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 95d47fcc..40e74e6f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.39.3 (provisional)
+
+* Fixing `NaN` size issue with `MultiSet.remove` when removing non-existent keys.
+
 ## 0.39.2
 
 * Fixing typings of low-level structure consuming methods (@jerome-benoit).
diff --git a/multi-set.js b/multi-set.js
index 3206af73..847c01dc 100644
--- a/multi-set.js
+++ b/multi-set.js
@@ -175,15 +175,20 @@ MultiSet.prototype.remove = function(item, count) {
   if (typeof count !== 'number')
     throw new Error('mnemonist/multi-set.remove: given count should be a number.');
 
-  var currentCount = this.multiplicity(item),
-      newCount = Math.max(0, currentCount - count);
+  var currentCount = this.items.get(item);
+
+  if (typeof currentCount === 'undefined') return;
+
+  var newCount = Math.max(0, currentCount - count);
 
   if (newCount === 0) {
-    this.delete(item);
+    this.items.delete(item);
+    this.size -= currentCount;
+    this.dimension--;
   }
   else {
     this.items.set(item, newCount);
-    this.size -= (currentCount - newCount);
+    this.size -= count;
   }
 
   return;
diff --git a/test/multi-set.js b/test/multi-set.js
index 4a17fe93..3c150d4f 100644
--- a/test/multi-set.js
+++ b/test/multi-set.js
@@ -311,6 +311,23 @@ describe('MultiSet', function() {
     assert.deepStrictEqual(top, [['i', 7]]);
   });
 
+  it('size should remain consistent (issue #197).', function() {
+    var set = new MultiSet();
+
+    set.add('one');
+    set.add('one');
+    set.remove('one');
+    set.remove('one');
+
+    assert.strictEqual(set.size, 0);
+    assert.strictEqual(set.dimension, 0);
+
+    set.remove('one');
+
+    assert.strictEqual(set.size, 0);
+    assert.strictEqual(set.dimension, 0);
+  });
+
   describe('helpers', function() {
 
     it('#.isSuperset', function() {