From e8055725bd13bdb7e58b5f7fb36412fb5c908f86 Mon Sep 17 00:00:00 2001
From: Rene Turcios <95189389+CloudCorpRecords@users.noreply.github.com>
Date: Thu, 22 Oct 2026 14:48:00 -0700
Subject: [PATCH] fix(response): preserve user-supplied content-type parameters
 on send

res.contentType = 'text/plain; version=0.0.4' was stripped to 'text/plain'
because send() split the type on ';' for formatter lookup and then used the
stripped value for the outgoing Content-Type header. Keep the parameters
aside for lookup, then restore them on the header. res.charSet() behavior
is unchanged.

Fixes restify/node-restify#1589.

Signed-off-by: Rene Turcios <95189389+CloudCorpRecords@users.noreply.github.com>
---
 lib/response.js       | 16 ++++++++++++-
 test/response.test.js | 52 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/lib/response.js b/lib/response.js
index 7119bb15..452fdda3 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -458,7 +458,16 @@ function patch(Response) {
                 );
             }
 
-            type = type.split(';')[0];
+            // Keep any user-supplied content-type parameters (e.g.
+            // "; version=0.0.4") so they survive on the outgoing header below.
+            // Only the base type is used for formatter lookup.
+            var contentTypeParams = '';
+            var paramIndex = type.indexOf(';');
+
+            if (paramIndex !== -1) {
+                contentTypeParams = type.substring(paramIndex);
+                type = type.substring(0, paramIndex);
+            }
 
             if (!self.formatters[type] && type.indexOf('/') === -1) {
                 type = mime.getType(type);
@@ -496,6 +505,11 @@ function patch(Response) {
 
             if (self._charSet) {
                 type = type + '; charset=' + self._charSet;
+            } else if (contentTypeParams) {
+                // Restore the parameters the user originally provided, e.g.
+                // res.contentType = 'text/plain; version=0.0.4' keeps the
+                // version parameter on the outgoing Content-Type header.
+                type = type + contentTypeParams;
             }
 
             // Update Content-Type header to the one originally set or to the
diff --git a/test/response.test.js b/test/response.test.js
index 8db5874b..fdb4de35 100644
--- a/test/response.test.js
+++ b/test/response.test.js
@@ -863,3 +863,55 @@ test(module, 'GH-1791: should send NaN as null with application/json', function(
         t.end();
     });
 });
+
+test(
+    module,
+    'GH-1589: should preserve content-type parameters set by the user',
+    function(t) {
+        SERVER.get('/content-type-params', function(req, res, next) {
+            res.contentType = 'text/plain; version=0.0.4; charset=utf-8';
+            res.send('hello');
+            return next();
+        });
+
+        STRING_CLIENT.get('/content-type-params', function(
+            err,
+            req,
+            res,
+            data
+        ) {
+            t.ifError(err);
+            t.equal(data, 'hello');
+            t.equal(
+                res.headers['content-type'],
+                'text/plain; version=0.0.4; charset=utf-8'
+            );
+            t.end();
+        });
+    }
+);
+
+test(
+    module,
+    'GH-1589: res.charSet still appends charset without duplicating params',
+    function(t) {
+        SERVER.get('/content-type-charset', function(req, res, next) {
+            res.contentType = 'text/plain';
+            res.charSet('utf-8');
+            res.send('hello');
+            return next();
+        });
+
+        STRING_CLIENT.get('/content-type-charset', function(
+            err,
+            req,
+            res,
+            data
+        ) {
+            t.ifError(err);
+            t.equal(data, 'hello');
+            t.equal(res.headers['content-type'], 'text/plain; charset=utf-8');
+            t.end();
+        });
+    }
+);