proposal: preserve fetching order

[flochtililoch]

This PR introduce a new behavior boolean attribute, preserve-order. This attribute is used by behaviors that "fetch" content, i.e. anytime there's a href attribute set, with an update action such as replace, replace-inner, etc. When present, we compute a unique id before the request is emitted, and store it on an attribute of the target element. When the response arrives, we read the attribute of the target element and compare it to the one we generated before the request was sent. If the attribute is set with a value that's different from the one set before the request, we assume this means another request/response cycle took place, and the response we're presently dealing with is "outdated", so we discard it.

To be discussed:

• naming: is "preserve-order" descriptive enough? should we use a boolean or an enum?
• visibility: should we make this feature public / documented or keep it "dark" for now?
• scope: should we think of this capability to be applied to other, non-fetching behaviors?

[palaparthi]

naming: is "preserve-order" descriptive enough?

"cancel-stale-requests" or "discard-stale-requests" might be more descriptive?

[adamstep]

I was curious how this is implemented in htmx. Looks like that library stores a queue of requests, and using an attribute there are different strategies for managing the queue if the element issues multiple requests. See the docs here: https://htmx.org/attributes/hx-sync/

Do you think a similar approach could work in Hyperview?

[adamstep]

Source code from htmx to deal with this: https://github.com/bigskysoftware/htmx/blob/master/src/htmx.js#L2980