Harper grammar actions — replacement & ignore (TASK-044)

Goal

Make glint's green grammar underlines actionable. On a grammar span at the cursor (Alt+;) or under a click, offer Harper's fix suggestions as replacement rows in the existing proofing popup, plus an Ignore action. Selecting a replacement applies Harper's edit to the buffer; Ignore suppresses that lint for the session.

Builds on TASK-043, which renders diagnostics only. Reuses the spell popup (spellOption/applySpell) plumbing.

Findings from live harper-ls 2.6 probe

These facts drove the design and narrowed scope:

1. Replacement works. textDocument/codeAction for a diagnostic's range returns quickfix CodeActions: a Harper-authored title (e.g. Replace with: "an") plus edit.changes[uri] = [{range, newText}]. Each also carries a HarperRecordLint telemetry command we ignore. The response also includes bare Command objects {command:"HarperIgnoreLint", arguments:[uri, lint], title:"Ignore Harper error."}.
2. HarperIgnoreLint is a no-op over LSP. Executing the command harper returns (verbatim args) yields null and never drops the lint — no changed re-publish after didChange, nothing written to ~/.config/harper-ls/ignored_lints/. So ignore must be implemented glint-side.
3. Add-to-dictionary is never offered for grammar lints (spelling-only concept). Dropped from scope.
4. Config reply bug. glint answers workspace/configuration with bare {}, causing harper's ERROR: Settings must contain a "harper-ls" key.. Reply must be {"harper-ls": {}}. Harmless to diagnostics but fixed here.

Scope

In: grammar-span replacement suggestions; client-side session ignore; the config fix. Out: add-to-dictionary for grammar; persistent (cross-launch) ignore; executing HarperIgnoreLint.

Design

grammar package

• Request/response correlation. Add pending map[int]chan json.RawMessage guarded by a mutex. In readLoop, the response case (method=="" && id present) routes the result to pending[id] if registered, else keeps the existing initialize-ready signal.
• CodeActions(path string, line, startRune, endRune int) ([]Action, error) — converts the rune range to UTF-16 using the client's tracked doc lines, sends textDocument/codeAction, waits on the reply channel with a ~400ms timeout, parses the result into []Action. Only actions carrying an edit become replacement Actions; their TextEdit ranges are mapped UTF-16 → rune coords. Bare-command actions (ignore) are not returned — ignore is glint-side. Dedup replacement Actions by title.
• Types:

  type Action struct { Title string; Edits []TextEdit } // replacement
  type TextEdit struct { StartLine, StartCol, EndLine, EndCol int; NewText string } // rune coords
  

• Config reply wraps each configuration item as {"harper-ls": {}}.
• runeColToUTF16(line, col) helper (inverse of existing utf16ToRuneCol).

Synchronous CodeActions (blocking ≤400ms) is acceptable: user-initiated, rare, harper is local. readLoop runs in its own goroutine, so the Update-thread block resolves without deadlock.

editor package

• GrammarSpanAt(row, col) (start, end int, ok bool) — the rune range of the grammar underline covering col, from grammarDiags[row].
• ReplaceRuneRange(startRow, startCol, endRow, endCol int, s string) — general range replacement (grammar fixes are single-line in practice; support multi-line for safety).
• Grammar session ignore: grammarIgnores map[string]struct{} keyed by code + "\x00" + flaggedText. IgnoreGrammar(code, text string) adds; a filter drops any incoming diag whose (code, buffer-substring at its range) is in the set. Mirrors spell's IgnoreWord. Because the key is content-based, it survives edits that move the span.

app package

• Extend spellKind with grammarFix (replacement) rows; the popup for a grammar span is built from CodeActions results + an i Ignore row + the existing g Grammar toggle.
• spellOption gains a way to carry an Action (edits) for grammarFix.
• openSpellPopupAt: spell word wins (existing check first); else if GrammarSpanAt hits, request CodeActions, build the grammar popup. Store the span (row,start,end) + rule code
  • flagged text for the Ignore action.
• applySpell: grammarFix → editor.ReplaceRuneRange for each edit (reverse doc order); ignore → editor.IgnoreGrammar(code, text) + re-filter current batch so the underline clears immediately.
• spellBar labels the new rows (1 …, i Ignore, g Grammar).

Testing (TDD)

• grammar: UTF-16↔rune round-trip; codeAction JSON → []Action parse (edits mapped, bare commands excluded, dedup by title); request/response correlation; config reply shape. Gated live test: real harper returns a replacement Action for "a a".
• editor: GrammarSpanAt hit/miss/boundary; ReplaceRuneRange single & multi-line; grammar-ignore filter drops matching diag, keeps others, content-keyed across an edit.
• app: grammar-span popup lists replacements + ignore; applying a fix mutates the buffer; ignore clears the underline; spell still wins when a word is both.

Acceptance criteria (revised)

• Grammar span at cursor offers Harper's fix suggestions in the Alt+; popup
• Selecting a fix applies harper's replacement to the buffer
• Ignore removes the grammar underline (glint-side session ignore, not HarperIgnoreLint)
• Add-to-dictionary — dropped: harper offers no add-to-dict for grammar lints