rune_devtools_extension #

Flutter DevTools extension for the rune package. Adds a rune tab to Flutter DevTools that inspects live RuneView instances in a running host app: their source strings, data contexts, parse-cache sizes, and last render errors.

How it works #

rune v1.18.0+ registers a VM service extension named ext.rune.inspect the first time a RuneView mounts (via dart:developer.registerExtension, which is compiled out in release builds). This package ships a Flutter web app that Flutter DevTools loads inside the rune tab; at debug time the app calls the service extension over the VM service protocol and renders the JSON payload as a list of expandable cards.

The extension is read-only in v0.1.0. You can:

• See every live RuneView (one card per instance).
• Copy its source string with one tap.
• Expand the data context as pretty-printed JSON.
• See the last render error (with the same caret-pointer shape RuneException.toString() produces).
• See the per-view parse cache size.

Requirements #

• rune: ^1.18.0 (must be listed as a direct dependency in the host app; the service extension ships with the main package).
• Flutter SDK with DevTools support (Flutter 3.16 and newer).
• The host app must be run in debug or profile mode. Release builds strip dart:developer.registerExtension.

Install #

Add the extension as a dev dependency of the host app:

dev_dependencies:
  rune_devtools_extension: ^0.1.0

Flutter DevTools auto-discovers the extension on the next flutter pub get + flutter run. No registration code is needed in the host.

Using the extension #

1. Run the host app: flutter run -d chrome (or any debug-mode target).
2. Open Flutter DevTools. The extension tab shows up as rune.
3. Mount at least one RuneView in the host app. Then tap Refresh on the extension's toolbar.
4. The tab lists every live RuneView. Tap a card to expand its source, data, cache stats, and last error.

If the extension tab reports Could not reach the host process, the host app most likely has no RuneView mounted yet (the service extension is registered lazily on the first mount) or is running in release mode. Mount a view or rerun in debug and retry.

Building the web app #

The compiled Flutter web bundle lives under extension/devtools/build/. It is not tracked in git: the output is ~30 MB of derived artefacts that have no place in source history. Instead, the bundle is produced on demand:

• For consumers installing from pub.flutter-io.cn: no action required. pub.flutter-io.cn publishes the bundle inside the package archive on each release, so dart pub get populates extension/devtools/build/ inside the cached package directly. Flutter DevTools picks it up.

• For consumers installing from a path-dependency (local monorepo development, git fork, etc.): run the build once after cloning:

  packages/rune_devtools_extension/tool/build_bundle.sh
  

  The script does flutter pub get + flutter build web + strips the debug .symbols sidecars. Rerun whenever you edit lib/main.dart.

• For maintainers of this package before publishing: run tool/build_bundle.sh, then dart pub publish. A .pubignore at the package root takes precedence over .gitignore during publish and deliberately omits extension/devtools/build/, so the freshly built bundle is included in the pub.flutter-io.cn archive even though git never tracks it.

The local CanvasKit bundle (~20 MB) cannot be replaced by a CDN fetch because Flutter DevTools serves the extension from a local scheme with a strict CSP that blocks external origins.

License #

MIT. See LICENSE.