ADR 0108: The half-typed command

Status

Accepted

Context

EditorViewport carries 153 data members. Eleven of them are one idea: what has been typed so far in a command that has not resolved yet. dd parks the operator between its two keys, 2d3w parks both counts, and "a, m, q, f and r each park the letter they are waiting on.

They were eleven separate members cleared by hand in resetVimPendingState(), which is called from 36 places. Adding a prefix meant remembering to add a line there, and the class of bug that follows is well represented in this project's history: the operator-abandoning guard in vimApplyNormalKey has caught four separate features that forgot to account for it.

A second copy of the same knowledge had already drifted. The check that decides whether a key begins a new command — and so whether a half-recorded dot should be dropped — tested six of the eleven fields and silently ignored mark, macro, textObject, registerName and awaitingRegister.

Decision

The eleven become a VimPending struct in gui/src/vim_pending.h.

reset() is *this = VimPending() rather than eleven assignments, so a member added later is covered the moment it is declared. count() replaces seven copies of std::max(1, count1) * std::max(1, count2), which is vim's rule that 2d3w deletes six words. idle() is the complete form of the drifted check.

All 93 references live in editor_viewport_vim.cpp, so nothing outside the vim layer had to change.

Consequences

Switching the drifted check to idle() changes behaviour in the five cases it had been ignoring. Eight cases were added first to pin what vim does there — . after ma, after `a, after "ayy, after "add, after ciw, after a recorded macro, after f, and with a count — and they pass both before and after the switch. That is evidence the two forms agree on the paths the suite reaches, not proof they agree everywhere.

This does not address the other 142 members. The vim state alone is about 32 of them once the macro and dot-repeat fields are counted, and the rest cluster by prefix into LSP, hover, find and render groups that could be given the same treatment. VimPending was taken first because it is the group with a live bug class attached, not merely the largest.