wehub-resource-sync
33 lines
1.5 KiB
TypeScript
33 lines
1.5 KiB
TypeScript
/**
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* Accumulate streamed tool-call `arguments` fragments without corrupting them.
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*
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* Providers stream tool-call arguments in one of two shapes:
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* - Incremental deltas: each chunk carries only the NEW fragment. These must
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* be concatenated verbatim — even when a fragment's leading bytes repeat the
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* tail of what we already have (e.g. the doubled `l` in `ls -ll`).
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* - Full snapshots: each chunk re-sends the ENTIRE accumulated arguments so
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* far. Concatenating those would duplicate the payload (issue #3701).
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*
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* We only dedup the snapshot case when it is UNAMBIGUOUS: an identical repeat,
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* or a growing superset that still starts with everything seen so far. Every
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* other fragment is treated as an incremental delta and appended as-is.
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*
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* A fuzzy suffix/prefix-overlap heuristic must NOT be used here: it silently
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* drops bytes from legitimate incremental deltas (turning `ll` into `l`, `xx`
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* into `x`), which trades a visible duplication bug for a silent truncation bug.
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*/
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export function appendToolCallArgumentDelta(current: unknown, incoming: unknown): string {
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const existing = typeof current === "string" ? current : "";
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const next = typeof incoming === "string" ? incoming : "";
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if (!existing) return next;
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if (!next) return existing;
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// Unambiguous snapshot repeat / growth — replace instead of concatenating.
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if (next === existing) return existing;
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if (next.startsWith(existing)) return next;
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// Incremental delta fragment — append verbatim (preserves repeated chars).
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return existing + next;
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}
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