Liveview example doesn't update view on click, but eats memory until OOM

[DestyNova]

Describe the bug 🐛
The liveview counter example from the Happyx website doesn't update the view when the button is clicked, but instead starts using more and more memory until OOM happens.

To Reproduce 👨‍🔬
Steps to reproduce the behavior:

1. Build the example program:

import happyx

var counter = remember 0

liveview:
  "/":
    {counter}
    tButton:
      "click me!"
      @click:
        counter += 1

serve "127.0.0.1", 5000:
  discard

2. Run the program and load it in Chromium (doesn't work at all in Firefox, says it can't connect to the websocket)
3. Click on the "click me!" button
4. Observe lack of update
5. Open htop and notice climbing memory and CPU usage in the server process
6. Refresh the browser and note that the state was updated (but only for the first click after each refresh; subsequent clicks send the same message that seems to have no effect, until reloading). Looking in the inspector, no response is ever received from the websocket.
7. Kill the process before it eats the universe

Expected behavior 🤔

1. Clicking should visibly update without needing to refresh the page (i.e. we should get a response from the websocket)
2. The process shouldn't leak memory and go bananas

Please complete the following information 📃

• OS: Linux
• OS Version 6.9.3, x86_64
• HappyX version 4.7.4
• HappyX project type: liveview (it seems ssr must be selected if creating the project with hqx, but it's the same without hqx)

• HappyX project language: nim
• Nim/Python version: 2.2.2
• HTTP Server: default (httpbeast?)
• Browser: Chromium
• Browser Version: 132.0.6834.83

[mirco-ackermann]

I tracked down the reason why the websocket in Firefox does not connect. Firefox sends
Connection: keep-alive, Upgrade as a single line.
In server.nim, contains called as
func contains*(values: HttpHeaderValues, value: string) will not work with that header because neither contains nor the http parser respects that Upgrade is a list so it compares "upgrade" to "keep-alive, Upgrade" which fails.

We could split the values at the comma in the parser but then we'd need to know which keys have values of list-type. Alternatively, we could add a new function like the following to replace our usage of contains:

  func containsListItem*(values: HttpHeaderValues, value: string): bool =
    ## Determines if `value` is one of the values inside `values`. Comparison
    ## is performed without case sensitivity, list of comma separated values   
    ## are split.
    result = false
    let value = value.toLowerAscii
    for val in seq[string](values):
      for v in val.split(","):
        let v = v.strip().toLowerAscii
        if v == value:   
          return true

After adding this function liveview seems to be broken on firefox in the same way as on chrome.

[DestyNova]

We could split the values at the comma in the parser but then we'd need to know which keys have values of list-type. Alternatively, we could add a new function like the following to replace our usage of contains:

Nicely done! The definition of HttpHeaderValues in Nim's httpcore does seem insufficient in that regard, given that comma-separated list semantics (instead of having multiple Connection: ... headers, in which case I think httpcore appends them into a bigger list) are well-defined in the HTTP semantics.

That bit should probably be opened as a bug on httpcore, where comma-separated parameter lists should be treated the same as multiple lines with the same header name (i.e. append them all into one list or set). But as you mentioned it would require specifying which fields can have list values.

[edit]
Separate issue opened on httpcore since it's more general than this.

[mirco-ackermann]

There is also parsing code in happyx which I assume is our culprit. From a casual glance it appears that happyx and httpcore both have this issue.