Add partitioned option

HISTORY.md

@@ -1,3 +1,8 @@
+unreleased
+==========
+
+  * Add `partitioned` option
+
 0.5.0 / 2022-04-11
 ==================
 

README.md

@@ -107,6 +107,17 @@ The given number will be converted to an integer by rounding down. By default, n
 `maxAge` are set, then `maxAge` takes precedence, but it is possible not all clients by obey this,
 so if both are set, they should point to the same date and time.
 
+##### partitioned
+
+Specifies the `boolean` value for the [`Partitioned` `Set-Cookie`](rfc-cutler-httpbis-partitioned-cookies)
+attribute. When truthy, the `Partitioned` attribute is set, otherwise it is not. By default, the
+`Partitioned` attribute is not set.
+
+**note** This is an attribute that has not yet been fully standardized, and may change in the future.
+This also means many clients may ignore this attribute until they understand it.
+
+More information about can be found in [the proposal](https://github.com/privacycg/CHIPS).
+
 ##### path
 
 Specifies the value for the [`Path` `Set-Cookie` attribute][rfc-6265-5.2.4]. By default, the path
@@ -275,6 +286,7 @@ $ npm run bench
 - [RFC 6265: HTTP State Management Mechanism][rfc-6265]
 - [Same-site Cookies][rfc-6265bis-09-5.4.7]
 
+[rfc-cutler-httpbis-partitioned-cookies]: https://tools.ietf.org/html/draft-cutler-httpbis-partitioned-cookies/
 [rfc-west-cookie-priority-00-4.1]: https://tools.ietf.org/html/draft-west-cookie-priority-00#section-4.1
 [rfc-6265bis-09-5.4.7]: https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-09#section-5.4.7
 [rfc-6265]: https://tools.ietf.org/html/rfc6265

index.js

@@ -172,6 +172,10 @@ function serialize(name, val, options) {
     str += '; Secure';
   }
 
+  if (opt.partitioned) {
+    str += '; Partitioned'
+  }
+
   if (opt.priority) {
     var priority = typeof opt.priority === 'string'
       ? opt.priority.toLowerCase()

test/serialize.js

@@ -113,6 +113,20 @@ describe('cookie.serialize(name, value, options)', function () {
     })
   })
 
+  describe('with "partitioned" option', function () {
+    it('should include partitioned flag when true', function () {
+      assert.equal(cookie.serialize('foo', 'bar', { partitioned: true }), 'foo=bar; Partitioned')
+    })
+
+    it('should not include partitioned flag when false', function () {
+      assert.equal(cookie.serialize('foo', 'bar', { partitioned: false }), 'foo=bar')
+    })
+
+    it('should not include partitioned flag when not defined', function () {
+      assert.equal(cookie.serialize('foo', 'bar', {}), 'foo=bar')
+    })
+  })
+
   describe('with "path" option', function () {
     it('should serialize path', function () {
       assert.equal(cookie.serialize('foo', 'bar', { path: '/' }), 'foo=bar; Path=/')