feat: add preventTouch option to Session.save method

README.md

@@ -398,7 +398,7 @@ req.session.reload(function(err) {
 })
 ```
 
-#### Session.save(callback)
+#### Session.save([preventTouch, callback])
 
 Save the session back to the store, replacing the contents on the store with the
 contents in memory (though a store may do something else--consult the store's
@@ -412,12 +412,29 @@ does not need to be called.
 There are some cases where it is useful to call this method, for example,
 redirects, long-lived requests or in WebSockets.
 
+If `preventTouch` is `true`, `store.touch` will not be called at the end of the
+HTTP response, which can be useful if using this library with something like 
+[Next.js getServerSideProps](https://github.com/expressjs/session/issues/870) to prevent [gssp-no-mutating-res](https://nextjs.org/docs/messages/gssp-no-mutating-res).
+
+**Note** `rolling: true` may still cause the above error.
+
 ```js
 req.session.save(function(err) {
   // session saved
 })
 ```
 
+```js
+// session saved + store.touch will not be called
+req.session.save(true)
+```
+
+```js
+req.session.save(true, function(err) {
+  // session saved + store.touch will not be called
+})
+```
+
 #### Session.touch()
 
 Updates the `.maxAge` property. Typically this is

index.js

@@ -213,6 +213,7 @@ function session(options) {
     var originalId;
     var savedHash;
     var touched = false
+    var preventTouchForReq = false
 
     // expose store
     req.sessionStore = store;
@@ -408,10 +409,23 @@ function session(options) {
         _reload.call(this, rewrapmethods(this, callback))
       }
 
-      function save() {
-        debug('saving %s', this.id);
-        savedHash = hash(this);
-        _save.apply(this, arguments);
+      function save(preventTouchOrCb, cb) {
+        debug('saving %s', this.id)
+        savedHash = hash(this)
+
+        var _cb = cb;
+
+        if (typeof preventTouchOrCb === 'function') {
+          _cb = preventTouchOrCb
+          preventTouchOrCb = false
+        }
+
+        if (preventTouchOrCb === true) {
+          preventTouchForReq = true
+          debug('touch disabled for this request via save(preventTouch=true)')
+        }
+
+        _save.call(this, _cb)
       }
 
       Object.defineProperty(sess, 'reload', {
@@ -465,7 +479,7 @@ function session(options) {
         return false;
       }
 
-      return cookieId === req.sessionID && !shouldSave(req);
+      return !preventTouchForReq && cookieId === req.sessionID && !shouldSave(req);
     }
 
     // determine if cookie should be set on response