Recalculate length on update

fixes isaacs#41

lib/lru-cache.js

@@ -150,20 +150,30 @@ LRUCache.prototype.dumpLru = function () {
 LRUCache.prototype.set = function (key, value, maxAge) {
   maxAge = maxAge || this._maxAge
   var now = maxAge ? Date.now() : 0
+  var len = this._lengthCalculator(value)
 
   if (hOP(this._cache, key)) {
+    if (len > this._max) {
+      del(this, this._cache[key])
+      return false
+    }
     // dispose of the old one before overwriting
     if (this._dispose)
       this._dispose(key, this._cache[key].value)
 
     this._cache[key].now = now
     this._cache[key].maxAge = maxAge
     this._cache[key].value = value
+    this._length += (len - this._cache[key].length)
+    this._cache[key].length = len
     this.get(key)
+
+    if (this._length > this._max)
+      trim(this)
+
     return true
   }
 
-  var len = this._lengthCalculator(value)
   var hit = new Entry(key, value, this._mru++, len, now, maxAge)
 
   // oversized objects fall out of cache automatically.

test/basic.js

@@ -182,6 +182,32 @@ test("lru recently gotten with weighed length", function (t) {
   t.end()
 })
 
+test("lru recently updated with weighed length", function (t) {
+  var cache = new LRU({
+    max: 8,
+    length: function (item) { return item.length }
+  })
+  cache.set("a", "A")
+  cache.set("b", "BB")
+  cache.set("c", "CCC")
+  t.equal(cache.length, 6) //CCC BB A
+  cache.set("a", "+A")
+  t.equal(cache.length, 7) //+A CCC BB
+  cache.set("b", "++BB")
+  t.equal(cache.length, 6) //++BB +A
+  t.equal(cache.get("c"), undefined)
+
+  cache.set("c", "oversized")
+  t.equal(cache.length, 6) //++BB +A
+  t.equal(cache.get("c"), undefined)
+
+  cache.set("a", "oversized")
+  t.equal(cache.length, 4) //++BB
+  t.equal(cache.get("a"), undefined)
+  t.equal(cache.get("b"), "++BB")
+  t.end()
+})
+
 test("set returns proper booleans", function(t) {
   var cache = new LRU({
     max: 5,