feat: add SSE compression exclusion within default predicate

[BenJeau]

Motivation

Discussed in this Github discussion from Axum's repo:

• SSE can't receive EventStream messages by browser tokio-rs/axum#2034 (reply in thread)

And had opened a docs PR within Axum's repo to add a note about compression for SSEs:

• docs: circumvent oddities with SSE and compression tokio-rs/axum#2585

If not careful or properly handled, general compression with SSE will result in missing some or all events.

Solution

Exclude SSEs from being compressed by checking the content type of text/event-stream within the DefaultPredicate

[FrankReh]

Could the problem have been that the compression buffer isn't flushed for the SSE case?

[BenJeau]

Could the problem have been that the compression buffer isn't flushed for the SSE case?

Potentially, I didn't had the time to investigate but saw that disabling compression resolved all my issues.

---

I can't close the linked issue #420 - if someone could, it would be great to cleanup the issues

[jplatte]

I'll try to remember to close it after the fix has shipped in a crates.io release.

[ekzhang]

Thanks for fixing this!

Besides text/event-stream, another candidate content type that involves dynamically pushing data is multipart/x-mixed-replace -- which is used sometimes in image tags: https://wiki.tcl-lang.org/page/multipart%2Fx-mixed-replace#:~:text=multipart%2Fx%2Dmixed%2Dreplace%20is%20an%20HTTP%20content%20type,content%20to%20the%20web%20browser.

(I think that one is a lot less common though)