The Invalid Surrogate Pair Bug: A Software Engineer's Tale of Emoji and Encoding
By
meysamazad
Slow-proofed and worth the wait. Worth its weight in flour.
Summary
A software engineer recounts their favorite bug story involving invalid surrogate pairs in Unicode/emoji handling. While migrating a legacy editor to a real-time collaborative experience using TipTap, ProseMirror, and Yjs CRDT, they encountered a bug where two emoji characters would cause the editor to break when entered together. The article explores the technical underpinnings of surrogate pairs in UTF-16 encoding, how emoji are represented, and the fascinating edge case that led to data loss. An interactive tool is provided for readers to explore the concepts.
Key quotes
· 3 pulledIf you're in the business of building things that run on computers long enough, I think you will eventually acquire a favorite bug story.
The bug: two emoji enter, none leave.
TipTap on top (itself a wrapper around ProseMirror), Yjs underneath handling the CRDT magic for real-time syncing. It worked well! Mostly.
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