devtools_extensions 0.0.13

A package for building and supporting extensions for Dart DevTools.

Dart & Flutter DevTools Extensions

Extend Dart & Flutter's developer tool suite, Dart DevTools, with a custom tool for your package. DevTools' extension framework allows you to build a tool for your Dart package that can leverage existing frameworks and utilities from DevTools (VM service connection, theming, shared widgets, utilities, etc.). When an app is connected to DevTools that depends on your package, your extension will show up in its own DevTools tab:

Follow the instructions below to get started, and use the end-to-end example for reference.

Table of contents

1. Setup your package to provide a DevTools extension
2. Create a DevTools extension
   • Where to put your source code
   • Development
   • Debugging
3. Publish your package with a DevTools extension
4. Resources and support

Setup your package to provide a DevTools extension

DevTools extensions must be written as Flutter web apps. This is because DevTools embeds extensions in an iFrame to display them dynamically in DevTools.

To add an extension to your Dart package, add a top-level extension directory:

foo
  extension/
  lib/
  ...

Under this directory, create the following structure:

extension
  devtools/
    build/
    config.yaml

The config.yaml file contains metadata that DevTools needs to load the extension.

name: foo
issueTracker: <link_to_your_issue_tracker.com>
version: 0.0.1
materialIconCodePoint: '0xe0b1'

Copy the config.yaml file content above and paste it into the config.yaml file you just created in your package. For each key, fill in the appropriate value for your package.

• name: the package name that this DevTools extension belongs to. The value of this field will be used in the extension page title bar. (required)

• issueTracker: the url for your issue tracker. When a user clicks the “Report an issue” link in the DevTools UI, they will be directed to this url. (required)

• version: the version of your DevTools extension. This version number should evolve over time as you ship new features for your extension. The value of this field will be used in the extension page title bar. (required)

  

• materialIconCodePoint: corresponds to the codepoint value of an icon from material/icons.dart. This icon will be used for the extension’s tab in the top-level DevTools tab bar. (required)

  

For the most up-to-date documentation on the config.yaml spec, see extension_config_spec.md

Now it is time to build your extension.

Create a DevTools extension

Where to put your source code

Only the pre-compiled output of your extension needs to be shipped with your pub package in order for DevTools to load it. To keep the size of your pub package small, we recommend that you develop your DevTools extension outside of your pub package. Here is the recommended package structure:

foo/  # formerly the repository root of your pub package
  packages/
    foo/  # your pub package
      extension/
        devtools/
          build/
            ...  # pre-compiled output of foo_devtools_extension
          config.yaml
    foo_devtools_extension/  # source code for your extension

Create the extension web app

From the directory where you want your extension source code to live, run the following command, replacing foo_devtools_extension with `<your_package_name>_devtools_extension``:

flutter create --template app --platforms web foo_devtools_extension

In foo_devtools_extension/pubspec.yaml, add a dependency on devtools_extensions:

devtools_extensions: ^0.0.10

In foo_devtools_extension/lib/main.dart, place a DevToolsExtension widget at the root of your app:

import 'package:devtools_extensions/devtools_extensions.dart';
import 'package:flutter/material.dart';

void main() {
  runApp(const FooDevToolsExtension());
}

class FooDevToolsExtension extends StatelessWidget {
  const FooDevToolsExtension({super.key});

  @override
  Widget build(BuildContext context) {
    return const DevToolsExtension(
      child: Placeholder(), // Build your extension here
    );
  }
}

The DevToolsExtension widget automatically performs all extension initialization required to interact with DevTools. From anywhere in your extension web app, you can access the globals extensionManager and serviceManager to send messages and interact with the connected app.

Utilize helper packages

Use package:devtools_app_shared for access to service managers, common widgets, DevTools theming, utilities, and more. See devtools_app_shared/example for sample usages.

Debug the extension web app

Use the Simulated DevTools Environment (recommended for development)

For debugging purposes, you will likely want to use the "simulated DevTools environment". This is a simulated environment that allows you to build your extension without having to develop it as an embedded iFrame in DevTools. Running your extension this way will wrap your extension with an environment that simulates the DevTools-to-DevTools extension connection. It also gives you access to hot restart and a faster development cycle.

1. Your DevTools extension.
2. The VM service URI for a test app that your DevTools extension will interact with. This app should depend on your extension’s parent package.
3. Buttons to perform actions that a user may trigger from DevTools.
4. Logs showing the messages that will be sent between your extension and DevTools.

The simulated environment is enabled by an environment parameter use_simulated_environment. To run your extension web app with this flag enabled, add a configuration to your launch.json file in VS code:

{
    ...
    "configurations": [
        ...
        {
            "name": "foo_devtools_extension + simulated environment",
            "cwd": "packages/foo_devtools_extension",
            "request": "launch",
            "type": "dart",
            "args": [
                "--dart-define=use_simulated_environment=true"
            ],
        },
    ]
}

or launch your app from the command line with the added flag:

flutter run -d chrome --dart-define=use_simulated_environment=true

Use a real DevTools Environment

To use a real DevTools environment, you will need to perform a series of setup steps:

1. Develop your extension to a point where you are ready to test your changes in a real DevTools environment. Build your flutter web app and copy the built assets from your_extension_web_app/build/web to your pub package's extension/devtools/build directory.

Use the build_and_copy command from package:devtools_extensions to help with this step.

cd your_extension_web_app;
flutter pub get;
dart run devtools_extensions build_and_copy --source=. --dest=../foo/extension/devtools

2. Prepare and run a test application that depends on your pub package. You'll need to change the pubspec.yaml dependency to be a path dependency that points to your local pub package source code. Once you have done this, run pub get on the test app, and run the application.

3. Start DevTools:

   • If you need local or unreleased changes from DevTools, you'll need to build and run DevTools from source. See the DevTools CONTRIBUTING.md for a guide on how to do this.

     Note: you'll need to build DevTools with the server and the front end to test extensions - see instructions.

   • If not, and if your local Dart or Flutter SDK version is >= 3.16.0-0.1.pre, you can launch the DevTools instance that was just started by running your app (either from a url printed to command line or from the IDE where you ran your test app). You can also run dart devtools from the command line.

4. Connect your test app to DevTools if it is not connected already, and you should see a tab in the DevTools app bar for your extension. The enabled or disabled state of your extension is managed by DevTools, which is exposed from an "Extensions" menu in DevTools, available from the action buttons in the upper right corner of the screen.

Publish your package with a DevTools extension

In order for a package to provide a DevTools extension to its users, it must be published with the expected content in the your_package/extension/devtools/ directory (see the setup instructions above).

1. Ensure the extension/devtools/config.yaml file exists and is configured per the specifications above.
2. Use the build_and_copy command provided by package:devtools_extensions to build your extension and copy the output to the extension/devtools directory:

cd your_extension_web_app;
flutter pub get;
dart run devtools_extensions build_and_copy --source=. --dest=../foo/extension/devtools

Then publish your package.

What if I don't want the extension/devtools/build/ contents checked into source control?

As a package author, the content that you check into your git repository is completely up to you. If you want the contents of extension/devtools/build/ to be git ignored, then you'll just need to ensure that the extension web app is always built and included in extension/devtools/build/ when you publish your package. To do so, add the following to a .pubignore file in the extension/devtools/ directory:

!build

This will ensure that, even if the extension/devtools/build directory has been been git ignored, the directory will still be included when publishing the package on pub.

To verify the published extension contents are always up to date, consider adding a tool script to your repo that looks something like this:

publish.sh

pushd your_extension_web_app

flutter pub get
dart run devtools_extensions build_and_copy --source=. --dest=../foo/extension/devtools

popd

pushd your_pub_package
flutter pub publish
popd

Resources and support

Please join the Flutter Discord server and then check out the #devtools-extension-authors channel to connect with other DevTools extension authors and the DevTools team.

For feature requests or bugs, please file an issue on the DevTools Github repository.