fix: support WebSocket upgrades in dev server#3823
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Vite's Connect-based dev server dispatches WebSocket upgrades as
'upgrade' events on the underlying http.Server rather than routing them
through middleware, so Deno.upgradeWebSocket() was never called and the
client hung in CONNECTING.
Now that deno#33342 lets Deno.upgradeWebSocket accept a raw node socket
via the `socket` option, the plugin can hand the socket off to Fresh's
existing ctx.upgrade() path. A WeakMap<Request, {socket, head}> kept on
globalThis acts as the side channel — populated by the plugin's upgrade
listener, consumed by ctx.upgrade() before it calls
Deno.upgradeWebSocket. The globalThis singleton is needed because
Vite's SSR runner evaluates context.ts separately from Deno's own load
of the plugin, leaving each with its own module instance.
Fixes #3350
bartlomieju
changed the title
This was referenced May 27, 2026
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Vite's Connect-based dev server dispatches WebSocket upgrades as
'upgrade' events on the underlying http.Server rather than routing them
through middleware, so
Deno.upgradeWebSocket()was never reached andthe client hung in CONNECTING. The plugin now attaches an upgrade
listener that hands the raw node socket off to Fresh's existing
ctx.upgrade()path.The plumbing leans on denoland/deno#33342, which taught
Deno.upgradeWebSocketto accept a{ socket, head }option forrequests that didn't come in through
Deno.serve. AWeakMap<Request, { socket, head }>kept onglobalThisacts as theside channel: the plugin's upgrade listener populates it,
ctx.upgrade()reads and clears it before calling Deno. The map liveson
globalThisbecause Vite's SSR runner evaluatescontext.tsseparately from Deno's own load of the plugin, so each side would
otherwise hold its own module-local instance.
Fixes #3350