fix(response): preserve user-supplied content-type parameters on send

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

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();
+        });
+    }
+);