feat: match JSON.stringify() behavior

The library will now match the behavior of the JSON.stringify() method:

- undefined is now encoded as nil (0xc0)
- undefined values in objects are now ignored

README.md

@@ -7,7 +7,7 @@ A fast [Node.js](http://nodejs.org) implementation of the latest [MessagePack](h
 ## Notes
 
 * This implementation is not backwards compatible with those that use the older spec. It is recommended that this library is only used in isolated systems.
-* `undefined` is encoded as `fixext 1 [0, 0]`, i.e. `<Buffer d4 00 00>`
+* `undefined` is encoded as `nil`
 * `Date` objects are encoded as `fixext 8 [0, ms]`, e.g. `new Date('2000-06-13T00:00:00.000Z')` => `<Buffer d7 00 00 00 00 df b7 62 9c 00>`
 * `ArrayBuffer` are encoded as `ext 8/16/32 [0, data]`, e.g. `Uint8Array.of(1, 2, 3, 4)` => `<Buffer c7 04 00 01 02 03 04>`
 

browser/decode.js

@@ -203,10 +203,6 @@ Decoder.prototype._parse = function () {
     case 0xd4:
       type = this._view.getInt8(this._offset);
       this._offset += 1;
-      if (type === 0x00) {
-        this._offset += 1;
-        return void 0;
-      }
       return [type, this._bin(1)];
     case 0xd5:
       type = this._view.getInt8(this._offset);

browser/encode.js

@@ -218,7 +218,7 @@ function _encode(bytes, defers, value) {
     var allKeys = Object.keys(value);
     for (i = 0, l = allKeys.length; i < l; i++) {
       key = allKeys[i];
-      if (typeof value[key] !== 'function') {
+      if (value[key] !== undefined && typeof value[key] !== 'function') {
         keys.push(key);
       }
     }
@@ -254,10 +254,9 @@ function _encode(bytes, defers, value) {
     bytes.push(value ? 0xc3 : 0xc2);
     return 1;
   }
-  // fixext 1 / undefined
   if (type === 'undefined') {
-    bytes.push(0xd4, 0, 0);
-    return 3;
+    bytes.push(0xc0);
+    return 1;
   }
   // custom types like BigInt (typeof value === 'bigint')
   if (typeof value.toJSON === 'function') {

lib/decode.js

@@ -189,10 +189,6 @@ Decoder.prototype.parse = function () {
     case 0xd4:
       type = this.buffer.readInt8(this.offset);
       this.offset += 1;
-      if (type === 0x00) {
-        this.offset += 1;
-        return void 0;
-      }
       return [type, this.bin(1)];
     case 0xd5:
       type = this.buffer.readInt8(this.offset);

lib/encode.js

@@ -246,7 +246,7 @@ function _encode(bytes, defers, value) {
 
       for (let i = 0, l = allKeys.length; i < l; i++) {
         key = allKeys[i];
-        if (typeof value[key] !== 'function') {
+        if (value[key] !== undefined && typeof value[key] !== 'function') {
           keys.push(key);
         }
       }
@@ -274,9 +274,9 @@ function _encode(bytes, defers, value) {
     case 'boolean': // false/true
       bytes.push(value ? 0xc3 : 0xc2);
       return 1;
-    case 'undefined': // fixext 1 / undefined
-      bytes.push(0xd4, 0, 0);
-      return 3;
+    case 'undefined':
+      bytes.push(0xc0);
+      return 1;
     default:
       // custom types like BigInt (typeof value === 'bigint')
       if (typeof value.toJSON === 'function') {

test/browser.js

@@ -73,7 +73,7 @@ describe('notepack (browser build)', function() {
       map: {},
       nil: null,
       bool: { 'true': true, 'false': false, both: [true, false, false, false, true] },
-      fixext: [undefined, new Date('2140-01-01T13:14:15.678Z'), undefined, new Date('2005-12-31T23:59:59.999Z')],
+      fixext: [null, new Date('2140-01-01T13:14:15.678Z'), null, new Date('2005-12-31T23:59:59.999Z')],
       utf8: ['α', '亜', '\uD83D\uDC26'],
       float: [1.1, 1234567891234567.5, Infinity, -Infinity, NaN]
     };

test/test.js

@@ -71,6 +71,7 @@ describe('notepack', function () {
 
   it('nil', function () {
     check(null, 'c0');
+    checkEncode(undefined, 'c0');
   });
 
   it('false', function () {
@@ -208,8 +209,7 @@ describe('notepack', function () {
     check(-Math.pow(2, 63) - 1024, 'd38000000000000000');
   });
 
-  it('fixext 1 / undefined', function () {
-    check(undefined, 'd40000');
+  it('fixext 1', function () {
     checkDecode([127, Buffer.from('a')], 'd4' + '7f' + '61');
   });
 
@@ -311,7 +311,7 @@ describe('notepack', function () {
       map: {},
       nil: null,
       bool: { 'true': true, 'false': false, both: [true, false, false, false, true] },
-      fixext: [undefined, new Date('2140-01-01T13:14:15.678Z'), undefined, new Date('2005-12-31T23:59:59.999Z')]
+      fixext: [null, new Date('2140-01-01T13:14:15.678Z'), null, new Date('2005-12-31T23:59:59.999Z')]
     };
     expected.map['a'.repeat(32)] = { a: 'a', b: 'b', c: 'c' };
     expected.map['b'.repeat(256)] = { a: { b: 1, c: 1, d: 1, e: { f: { g: 2, h: 2 } } } };
@@ -322,6 +322,19 @@ describe('notepack', function () {
     expect(notepack.decode(notepack.encode(expected))).to.deep.equal(expected);
   });
 
+  it('undefined as array elem or map value', function () {
+    const value = {
+      a: undefined,
+      b: null,
+      c: [undefined, null]
+    };
+    const expected = {
+      b: null,
+      c: [null, null]
+    };
+    expect(notepack.decode(notepack.encode(value))).to.deep.equal(expected);
+  });
+
   it('10000', function () {
     const fixture = require('./fixtures/10000.json');