Code Editor

Crate: editors/code. Opens any File{Text} node; lowest priority so specialised editors (markdown WYSIWYG, flow) win for their kinds, with “Open with…” to override.

Architecture

• Document in Rust: ropey::Rope + version + undo stack. Edits become core patches (ADR-0009 Patches not snapshots).
• Backend behind a trait (CodeEditorBackend): CodeMirror 6 today via JS Interop Boundary; a Rust-native view later (Rust-native Editor Candidates).
• Decorations are data: Highlight, Fold, Diagnostic, InlayHint, Gutter produced by Indexing (tree-sitter) and LSP and Terminal, consumed by any backend. The CodeMirror bundle therefore ships no language packages.

Languages (initial)

Language	Grammar	LSP	Why first
Rust	tree-sitter-rust	rust-analyzer	dogfooding
Julia	tree-sitter-julia	LanguageServer.jl	host of Flow Editor targets (Lux.jl, MTK)
Go	tree-sitter-go	gopls	mature, simple
Unison	community grammar (verify)	ucm	database-backed codebase = a natural Source
Lean 4	tree-sitter-lean (verify)	lake serve	infoview as an extra panel

Each is a LanguageContribution in editors/code/src/languages/, proving the contribution point works (Example - Language).

Features by phase

1. Open/edit/save, highlighting from tree-sitter, folding, search.
2. LSP: diagnostics, hover, completion, go-to-definition (which is a graph edge!), references.
3. Semantic tokens, inlay hints, code actions, format.
4. “Show AST”, “show call graph of this function” → open a GraphView in the Graph View.

Big cases

Backend chosen by measured size — see Case Selector (design).

Unicode input

\name → symbol with a dropdown, in this editor and every other input: Unicode Input (design, not built).

Unison note

Unison stores code in a codebase DB, not files. A UnisonSource extension (definitions as nodes, dependency edges) would make Moonkale one of the few editors that shows Unison the way Unison thinks. Good showcase; later phase.

Designs not built yet

Removed from editors/code/src as comment-only files in Milestone 18 phase 1:

• Decorations (decorations.rs) in a neutral form — Highlight { range, token }, Fold, Diagnostic, InlayHint, Gutter — produced by the index/LSP and consumed by any backend. Today diagnostics and wiki-link marks go to CodeMirror in their own messages, and highlighting is the bundle’s (P-093).
• Document (document.rs): rope + version + undo stack + node id, turning backend edits into core patches and applying incoming changes (external change → reconcile or prompt). Today ext-api::Document holds a String and the view owns undo.
• A Rust-native backend (backend/native.rs): a virtualised Dioxus text view or a wgpu text renderer over the same rope and decorations. The Rust editor that exists (Code Editor Implementations) is a separate extension on dioxus-code-editor, not this backend.