diaryx_extism 1.3.0

Extism-based third-party plugin runtime for Diaryx
Documentation

diaryx_extism

Extism-based third-party plugin runtime for Diaryx.

Loads WebAssembly plugin modules via the Extism runtime and adapts them to diaryx_core plugin traits. Guest plugins communicate with the host through a JSON protocol (protocol.rs).

Plugin directory structure

~/.diaryx/plugins/
  my-plugin/
    plugin.wasm      # The WASM module
    manifest.json    # Cached guest manifest
    config.json      # Plugin config sidecar

Guest-exported functions

Function Input Output When called
manifest "" GuestManifest JSON At load time
init PluginContext JSON "" Plugin initialization
on_event GuestEvent JSON "" File/workspace events
handle_command CommandRequest JSON CommandResponse JSON Command dispatch
get_config "" config JSON Config read
set_config config JSON "" Config write

GuestManifest supports optional requested_permissions:

  • defaults (PluginPermissions) for install-time defaults
  • reasons (HashMap<String, String>) for permission rationale text

Host functions available to guests

Function Description
host_log Plugin logging
host_read_file / host_list_files / host_file_exists Workspace reads
host_write_file / host_write_binary Workspace writes (create/edit split by file existence)
host_delete_file Workspace deletes
host_http_request HTTP request bridge (feature-gated, supports optional timeout_ms)
host_storage_get / host_storage_set Plugin persistent storage
host_run_wasi_module Execute a WASI module loaded from plugin storage (feature-gated)
host_emit_event / host_ws_request / host_get_timestamp Eventing and utility functions

Permission enforcement

Permissions are checked in host functions via HostContext.permission_checker.

  • If no checker is configured, host calls are denied.
  • HostContext::with_fs() defaults to DenyAllPermissionChecker.
  • Loader updates runtime plugin_id from the guest manifest id, so checks are keyed to the canonical plugin ID.

Provided checkers:

  • DenyAllPermissionChecker — denies every request
  • FrontmatterPermissionChecker — reads root frontmatter plugins config and delegates to diaryx_core::plugin::permissions::check_permission

Storage keys are plugin-scoped in host functions ({plugin_id}:{key}), so one plugin cannot read another plugin's storage by key collision.