stream: handle setEncoding after buffered data#63973
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Signed-off-by: Matteo Collina <hello@matteocollina.com>
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Fixes
Readable.prototype.setEncoding()when it is called after byte data has already been buffered but before that data is consumed.This addresses the Node.js core stream behavior behind nodejs/undici#5002: if
setEncoding('utf8')is applied after bytes are buffered, split multibyte UTF-8 sequences must be handed to a singleStringDecoderso consumers do not seeU+FFFDcorruption at chunk boundaries.When the buffered data ends with an incomplete multibyte sequence and the stream has ended, the new decoder needs to be finalized so it can emit the replacement character instead of dropping the bytes.
Tests cover:
setEncoding()after split multibyte data is buffered_read()buffered the first chunkRefs: #63570
Refs: nodejs/undici#5002