From caa4f68ee8d32474676fa29cc2086dcc1d62208b Mon Sep 17 00:00:00 2001
From: Andrea Polverino <36574883+andvea@users.noreply.github.com>
Date: Fri, 14 Feb 2025 17:20:53 +0100
Subject: [PATCH] feat: Extend res.links() to allow adding multiple links with
 the same rel (closes #2729) (#4885)

---
 History.md        |  1 +
 lib/response.js   | 19 +++++++++++++++----
 test/res.links.js | 18 ++++++++++++++++++
 3 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/History.md b/History.md
index 021315c5..98cfb14c 100644
--- a/History.md
+++ b/History.md
@@ -11,6 +11,7 @@ unreleased
 * Remove unused `depd` dependency
 * Add support for `Uint8Array` in `res.send`
 * Add support for ETag option in res.sendFile
+* Extend res.links() to allow adding multiple links with the same rel
 * deps: debug@^4.4.0
 * deps: body-parser@^2.1.0
 * deps: router@^2.1.0
diff --git a/lib/response.js b/lib/response.js
index b1dfcb23..9362d0ed 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -80,7 +80,11 @@ res.status = function status(code) {
  *
  *    res.links({
  *      next: 'http://api.example.com/users?page=2',
- *      last: 'http://api.example.com/users?page=5'
+ *      last: 'http://api.example.com/users?page=5',
+ *      pages: [
+ *        'http://api.example.com/users?page=1',
+ *        'http://api.example.com/users?page=2'
+ *      ]
  *    });
  *
  * @param {Object} links
@@ -88,11 +92,18 @@ res.status = function status(code) {
  * @public
  */
 
-res.links = function(links){
+res.links = function(links) {
   var link = this.get('Link') || '';
   if (link) link += ', ';
-  return this.set('Link', link + Object.keys(links).map(function(rel){
-    return '<' + links[rel] + '>; rel="' + rel + '"';
+  return this.set('Link', link + Object.keys(links).map(function(rel) {
+    // Allow multiple links if links[rel] is an array
+    if (Array.isArray(links[rel])) {
+      return links[rel].map(function (singleLink) {
+        return `<${singleLink}>; rel="${rel}"`;
+      }).join(', ');
+    } else {
+      return `<${links[rel]}>; rel="${rel}"`;
+    }
   }).join(', '));
 };
 
diff --git a/test/res.links.js b/test/res.links.js
index 240b7fcf..40665fd5 100644
--- a/test/res.links.js
+++ b/test/res.links.js
@@ -43,5 +43,23 @@ describe('res', function(){
       .expect('Link', '<http://api.example.com/users?page=2>; rel="next", <http://api.example.com/users?page=5>; rel="last", <http://api.example.com/users?page=1>; rel="prev"')
       .expect(200, done);
     })
+
+    it('should set multiple links for single rel', function (done) {
+      var app = express();
+
+      app.use(function (req, res) {
+        res.links({
+          next: 'http://api.example.com/users?page=2',
+          last: ['http://api.example.com/users?page=5', 'http://api.example.com/users?page=1']
+        });
+
+        res.end();
+      });
+
+      request(app)
+      .get('/')
+      .expect('Link', '<http://api.example.com/users?page=2>; rel="next", <http://api.example.com/users?page=5>; rel="last", <http://api.example.com/users?page=1>; rel="last"')
+      .expect(200, done);
+    })
   })
 })