Plugin Capability Matrix

Audit of the plugin protocol (v3) as of 0.21.x: what the protocol declares, what the host actually implements, and what the bundled plugins use. This is the “take stock” pass after the 0.8 plugin work (issue #296). For the protocol itself — message formats, examples, contribution/teardown rules — see Plugin Development.

Capabilities

Capabilities are declared by a plugin in its register_language_provider action and stored as Capability variants (src/plugin/types.rs). The host routes them via PluginManager::provider_for (src/plugin/manager.rs).

Note on highlight: real syntax highlighting flows through syntax plugins (kind = "syntax", a .sublime-syntax file fed to syntect — see the bundled toml/typescript/dockerfile/nginx/justfile plugins), not through language-provider capabilities. The highlight capability is documented as reserved for future provider-driven highlighting; today registering it has no effect.

Actions

Every action the host accepts, dispatched in App::handle_plugin_action (src/app/refresh.rs). Unknown actions are silently ignored.

Teardown status: every stateful registration and set_* action stamps PluginContributions and is cleared by App::teardown_plugin_contributions (src/app/mod.rs). No teardown gaps were found in this audit.

Protocol v1 git actions (set_file_statuses, set_blame_data, set_status_bar_git_info) were removed in 0.11.22 along with the retired shell-script git plugins; git features are built in. They are listed in the version history in Plugin Development only.

Bundled plugins

Gaps and follow-ups

1. Reserved capabilities (hover, definition) still need concrete UI and contribution models. diagnostics uses the protocol 3 request/response transport and is implemented by the host; the bundled Python provider uses Ruff when available.
2. The language-provider fold pipeline has bundled consumers — register_language_provider + Capability::Fold + set_fold_regions are used by the bundled rust (issue #599), go (issue #600), python (issue #601), json (issue #604), sh (issue #605), yaml (issue #603), and terraform (issue #782) language provider plugins. The rust and go plugins register the fold capability for .rs and .go files via the shared brace_fold detector (#598); the python plugin uses the shared indent_fold detector; the json plugin uses brace_fold_with_brackets, a brace_fold variant that also folds […] arrays; the sh plugin uses shell_brace_fold, a shell-specific variant that handles # line comments, single/double quoted strings, and heredocs; the yaml plugin uses the shared yaml_fold detector — the same algorithm the built-in crate::yaml_fold::detect_fold_regions re-exports, so plugin-enabled and built-in YAML folding agree; the terraform plugin uses hcl_brace_fold, an HCL-specific variant that handles #/////* */ comments, double-quoted strings, and heredocs for .tf, .tfvars, and .hcl files. Built-in YAML folding (compute_file_load in src/app/loader.rs) is unchanged in this phase — it still dispatches to yaml_fold::detect_fold_regions directly, and the plugin’s regions only take over when the plugin is enabled (existing override precedence in handle_plugin_set_fold_regions). Retiring the built-in dispatch is a separate follow-up (issue #603 phase 2), deferred until bundled plugins have a default-enabled mechanism. Provider routing supports exact filenames, filename globs, extensions, and shebang interpreters. The host reads and caches the shebang during file load; filename specificity wins over extension and shebang matches (see #836).
3. Capability::Highlight is declared but routes to nothing. Either implement provider-driven highlighting in v3 or re-document it as reserved alongside hover/definition. Not yet tracked in a dedicated issue; candidate checklist item for #481.
4. status_facts/set_status_facts (0.18.x) resolves the protocol gap that blocked issue #606 (k8s manifest awareness): the epic’s “per-language statusbar facts” item (originally #482, merged into #602) had no protocol surface, and #606 was filed as a proposal rather than a build order for exactly that reason. The new capability is deliberately generic free text, not a structured breadcrumb — the bundled k8s plugin uses it for both candidate features from #606 (resource identity and multi-doc per-kind counts) combined into one string, rather than adding a second breadcrumb capability. The additive on_content_cursor_change event closes the per-cursor gap: it sends debounced, one-based line and column coordinates, and the bundled k8s plugin now reports the resource containing the cursor.