fix(ws): decode TEXT payloads per code point, not per byte

[ehsanmok]

Summary

WsFrame.text_payload() validated its payload as UTF-8 per RFC 6455 8.1 and then decoded it with s += chr(Int(b)) per byte, which maps each byte to the code point of the same value. Every non-ASCII TEXT frame came back with one character per byte:

WsFrame.text("café 日本語").text_payload()  # -> "café æ¥æ¬èª"

This is user-visible on both sides of the connection today. WsClient.recv() builds its WsMessage from text_payload() (flare/ws/client.mojo:766), and both WsServer echo paths go through it (flare/ws/server.mojo:513, and the documented handler example at line 331).

The validation on the preceding line already guarantees well-formed UTF-8, so the loop collapses into the bulk constructor with no new failure mode. Worth stating explicitly, since it is the reason this substitution is safe here and not everywhere: String(unsafe_from_utf8=...) runs the stdlib validator internally despite its name (documented in this tree at docs/benchmark.md:705-708 and flare/http/proto/ascii.mojo:51-61), and on invalid input that validator aborts the process under -D ASSERT=all. It cannot fire here because line 496 has already rejected invalid payloads.

Same shape as the Response.text() fix in #9.

Not in scope

Request.text() (flare/http/request.mojo:419) and MultipartPart.text() (flare/http/multipart.mojo:232, reached publicly via MultipartForm.value()) carry the identical loop and are identically broken, confirmed locally. Their bytes are caller-supplied rather than pre-validated, so the plain substitution would trade mojibake for a remotely-triggerable abort on an assert-enabled build. They need validate-then-copy and are tracked separately.

Test plan

• test_encode_decode_roundtrip_text_utf8 added, covering 2-, 3- and 4-byte sequences; verified it FAILS on the unfixed decoder and passes with the fix
• pixi run test-ws 34/34
• pixi run test-ws-permessage-deflate 12, test-ws-h2 6, test-ws-h2-roundtrip 1, test-ws-stateful-handler 1, test-conformance-ws OK
• pixi run format-check clean

Made with Cursor