Add ANSI.replay to collapse captured repaints - #623
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Spinners and progress bars repaint by moving the cursor, so a capture of the stream (a log file, StdoutRouter's duplicate output, test output) holds one frame per tick. ANSI.strip_codes deletes those control sequences instead of applying them, which leaves every frame side by side rather than overwriting: \r disappears, and CSI_SEQUENCE matches neither the parameterless (\e[K) nor the private (\e[?25l) forms, so those survive as text. ANSI.replay applies the stream's viewport-independent controls -- CR/LF/BS, relative cursor moves, erase-line, insert/delete-line, cursor save/restore -- to a line grid and returns the text the repaints settled on. Presentation sequences and control-string payloads (OSC, DCS) are dropped, as a terminal drops them, and so are operations that assume a viewport (absolute positioning, display erasure): a capture does not record scrolling, so a screen coordinate has no buffer row to map onto. Shopify's dev CLI attaches its `dev up` log to error reports, where a 450KB capture replays to 41KB of what the developer actually saw. The stream is parsed by the VT500-series state machine (https://vt100.net/emu/dec_ansi_parser), so aborted, garbled, cut-off, and control-embedded sequences resolve the way a real terminal resolves them. Printable runs, string payloads, and well-formed CSI bodies move in bulk; a fuzz test pins the rest of the input space to no-raise, valid-UTF-8, control-free output. There is no viewport: a capture has no scrollback to lose, so height is unbounded and cursor moves, gap padding and insert-line are capped instead. Only rows a control sequence conjures count against that cap, so an ordinary long capture never exhausts it. Co-authored-by: River <river@shopify.com> Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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tl;dr - add
ANSI.replaythat removes noise from log files piped fromcli-uioutput.Spinners and progress bars repaint by moving the cursor, so a capture of the stream (a log file, StdoutRouter's duplicate output, test output) holds one frame per tick. ANSI.strip_codes deletes those control sequences instead of applying them, which leaves every frame side by side rather than overwriting: \r disappears, and CSI_SEQUENCE matches neither the parameterless (\e[K) nor the private (\e[?25l) forms, so those survive as text.
ANSI.replay applies the stream's viewport-independent controls -- CR/LF/BS, relative cursor moves, erase-line, insert/delete-line, cursor save/restore -- to a line grid and returns the text the repaints settled on. Presentation sequences and control-string payloads (OSC, DCS) are dropped, as a terminal drops them, and so are operations that assume a viewport (absolute positioning, display erasure): a capture does not record scrolling, so a screen coordinate has no buffer row to map onto. Shopify's dev CLI attaches its
dev uplog to error reports, where a 450KB capture replays to 41KB of what the developer actually saw.There is no viewport: a capture has no scrollback to lose, so height is unbounded and cursor moves, gap padding and insert-line are capped instead. Only rows a control sequence conjures count against that cap, so an ordinary long capture never exhausts it.