chore: replace the deprecated json helper with Response.json - #16804
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Nic-Polumeyv wants to merge 11 commits into
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chore: replace the deprecated json helper with Response.json#16804Nic-Polumeyv wants to merge 11 commits into
json helper with Response.json#16804Nic-Polumeyv wants to merge 11 commits into
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Install the latest version of pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/cf3e618b511a96a496eb06a0e69523a078551d44Open in |
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Nic-Polumeyv
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Response.json in runtime responsesjson helper with Response.json
Rich-Harris
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Aug 14, 2026
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#16794) On Node, `setResponse` streams every `response.body` through a reader loop, so a response without a pre-computed `content-length` header is served with chunked transfer encoding. That is why the runtime can't move off the deprecated `json`/`text` helpers, whose only load-bearing job is stamping that header, and why a plain `Response.json` returned from an endpoint is served chunked today. Every other runtime derives the header from fixed bodies at serve time. `setResponse` now races the body's first reads against a `setImmediate` deadline before writing the head. A fixed body settles value-then-done on microtasks, so it is sent with a measured `content-length`; a body that leaves a read pending is a genuine stream and goes through the existing streaming path unchanged, with its headers delayed by at most one tick. Nothing is added when the response already carries a `content-length` or a `transfer-encoding` (proxied responses can carry the latter, and the pair would be invalid). Same approach as hono's node-server. `json`/`text` are untouched. Retiring them internally becomes a follow-up; its one catch is the `http.response.body.size` span attribute, which reads the `content-length` header. #16804 is stacked on this.
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With #16794,
setResponsederivescontent-lengthfrom fixed bodies, so runtime responses no longer need thejsonhelper to be served correctly on Node. This switches the runtime'sjsoncall sites to the nativeResponse.json(deprecated by #15448).textcall sites stay:new Responsewith a string body adds a defaulttext/plaincontent-type where the helper adds none, so replacing those changes response headers and is a separate decision. Tracing is unaffected, since page and error documents still go throughtext.Stacked on #16794; retarget to
version-3once it merges.