Review feedback (MINOR): char::is_whitespace returns false for
zero-width format codepoints (U+200B ZWSP, U+200C ZWNJ, U+200D ZWJ,
U+2060 WORD JOINER, U+FEFF ZWNBSP / BOM). The original normalise
pass let them through to the LLM where they waste tokens without
contributing any natural-language content.
Makes the decision explicit: these chars STRIP entirely rather than
collapse to a space. Collapsing would silently insert a word break
where the source had none ("hello<FEFF>world" → "hello world"
would merge two words into a space-separated pair that the original
author did not intend). Stripping preserves the original token
boundaries and drops the invisible noise.
Three new tests:
- zero_width_format_chars_strip_entirely — exhaustive coverage of
all five handled codepoints.
- zero_width_chars_do_not_break_adjacent_whitespace_collapsing —
"hello <FEFF> world" still collapses to "hello world" (the
strip does not leave behind an artefact that breaks the whitespace
collapse pass).
- leading_bom_is_stripped — a BOM at segment start, the common
artefact pattern when Whisper consumes an encoded file.
New crates/ai-formatting/src/to_plain_text.rs module with one public
function: to_plain_text(&[Segment]) -> String.
Rules the function enforces:
- each segment's text is whitespace-normalised (any run of unicode
whitespace collapses to a single ASCII space, so tabs, newlines,
and NBSPs never reach the LLM),
- empty and whitespace-only segments are dropped,
- remaining segments are joined with a single ASCII space,
- the joined string is normalised again (so a segment ending in a
space followed by one starting in a space does not produce a double
space) and trimmed end-to-end.
pipeline.rs's inline join is replaced with this call. Whisper's
timestamp fields (Segment.start / .end) are carried separately and
never reach the LLM by construction — the "timestamps stripped"
half of brief item #29's acceptance falls out of using Segment.text
alone. The work the module actually adds is whitespace discipline
and the tested boundary (empty input, empty-only input, NBSPs,
pathological whitespace runs, idempotence, double-space at join
boundaries).
Source: Scriberr PR #288 — feeding raw Whisper JSON (with timestamps
and per-segment structure) degraded cleanup quality; plain-text
input raised it back.
