fix: encoding of previously-used values

[lsthornt]

I had more occurrences of #36 in my project, and I was able to isolate the issue much better. I believe this test is the absolute minimal case.

Reused values certainly work in many other scenarios, but this specific setup results in a circular reference for the third object key: data.

• if the value for data is not an object, no failure occurs
• if 'baz' is not used as object value in 'foo', or if it is an object value in bar, no failure occurs.

---

In my codebase, foo, bar, and data are all independent promises resolved from a Remix loader. When data resolves prior to bar, no failure occurs. The PREVIOUSLY_RESOLVED value must resolve prior to the data object. In doing so, it seems it taints either the values or hydrated cache in unflatten

[lsthornt]

I've added what I believe to be a fix.

It seemed like the issue was with encoding rather than decoding. The object encoded after the reused value would end up decoding starting at a preceding index, leading to the circular reference, as I saw in my original issue.

The fix doesn't feel elegant, but I've given it some testing in my real project and it seems sound. @jacob-ebey hoping can take a closer and wiser look.

[nick-potts]

I'm really glad you managed to track this one down - I spent far too long trying to create a minimal reproduction.

[lsthornt]

Me too, I really just got lucky with a reproducible example in my project.

@nick-potts it would be great to know if this fix resolves your issue too – any extra test time is helpful. Here is the patch I'm using:

diff --git a/node_modules/turbo-stream/dist/turbo-stream.js b/node_modules/turbo-stream/dist/turbo-stream.js
index 18027f9..2222cb7 100644
--- a/node_modules/turbo-stream/dist/turbo-stream.js
+++ b/node_modules/turbo-stream/dist/turbo-stream.js
@@ -141,6 +141,8 @@ function encode(input, options) {
                         const id = flatten_js_1.flatten.call(encoder, resolved);
                         if (Array.isArray(id)) {
                             controller.enqueue(textEncoder.encode(`${utils_js_1.TYPE_PROMISE}${deferredId}:[["${utils_js_1.TYPE_PREVIOUS_RESOLVED}",${id[0]}]]\n`));
+                            encoder.index++;
+                            lastSentIndex++;
                         }
                         else if (id < 0) {
                             controller.enqueue(textEncoder.encode(`${utils_js_1.TYPE_PROMISE}${deferredId}:${id}\n`));
@@ -161,6 +163,8 @@ function encode(input, options) {
                         const id = flatten_js_1.flatten.call(encoder, reason);
                         if (Array.isArray(id)) {
                             controller.enqueue(textEncoder.encode(`${utils_js_1.TYPE_ERROR}${deferredId}:[["${utils_js_1.TYPE_PREVIOUS_RESOLVED}",${id[0]}]]\n`));
+                            encoder.index++;
+                            lastSentIndex++;
                         }
                         else if (id < 0) {
                             controller.enqueue(textEncoder.encode(`${utils_js_1.TYPE_ERROR}${deferredId}:${id}\n`));
diff --git a/node_modules/turbo-stream/dist/turbo-stream.mjs b/node_modules/turbo-stream/dist/turbo-stream.mjs
index f95b077..7e0d25c 100644
--- a/node_modules/turbo-stream/dist/turbo-stream.mjs
+++ b/node_modules/turbo-stream/dist/turbo-stream.mjs
@@ -452,6 +452,8 @@ function encode(input, options) {
 `
                     )
                   );
+                  encoder.index++;
+                  lastSentIndex++;
                 } else if (id2 < 0) {
                   controller.enqueue(
                     textEncoder.encode(`${TYPE_PROMISE}${deferredId}:${id2}
@@ -480,6 +482,8 @@ function encode(input, options) {
 `
                     )
                   );
+                  encoder.index++;
+                  lastSentIndex++;
                 } else if (id2 < 0) {
                   controller.enqueue(
                     textEncoder.encode(`${TYPE_ERROR}${deferredId}:${id2}

[nick-potts]

Yep, gave it a shot and it works an absolute treat. Mine's probably a great stress test on it, lots of very similar data with lots of nested keys with the same name. Also passing about 50-200 promises per page load.

[nick-potts]

woot woot

[nick-potts]

I tried 2.2.2, but its reporting an internal error. Will get back to you when I understand it.