feat: migrate dartpad injection to jaspr

[schultek]

Migrate dartpad injection to Jaspr.

Part of #12548

Presubmit checklist

• If you are unwilling, or unable, to sign the CLA, even for a tiny, one-word PR, please file an issue instead of a PR.
• If this PR is not meant to land until a future stable release, mark it as draft with an explanation.
• This PR follows the Google Developer Documentation Style Guidelines—for example, it doesn't use i.e. or e.g., and it avoids I and we (first-person pronouns).
• This PR uses semantic line breaks
  of 80 characters or fewer.

[gemini-code-assist]

Summary of Changes

Hello @schultek, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly refactors how DartPad examples are embedded and displayed on the site. By transitioning to a Jaspr-native component-based solution, it aims to improve the integration, maintainability, and potentially the performance of DartPad instances, moving away from a custom JavaScript injection method.

Highlights

• Jaspr Migration for DartPad Injection: The mechanism for injecting DartPad examples into the site has been migrated to use Jaspr components, replacing the previous JavaScript-based approach.
• New DartPad Components Introduced: New DartPadInjector and DartPadWrapper components have been added. DartPadWrapper handles server-side rendering of code blocks, while DartPadInjector manages the client-side embedding and interaction with the DartPad iframe.
• Removal of Legacy JavaScript: The inject_dartpad.dart.js file, which previously handled DartPad injection, has been removed, simplifying the client-side scripting.
• Content File Cleanup: Numerous markdown content files across the site have been updated to remove the now-obsolete js frontmatter entries, as the new Jaspr-based system automatically handles DartPad embedding.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request is a great improvement, migrating the DartPad injection logic from a JavaScript-based solution to a pure Jaspr implementation. The new code is well-structured, using modern Dart features like records and extension types for JS interop, and correctly separates server-side and client-side logic. The removal of the old JS file and the cleanup in the markdown files are all consistent with this migration.

I've found one potential regression where the runAutomatically option for DartPads seems to have been dropped. I've left a specific comment with a suggestion to fix it. Other than that, the changes look excellent.

[flutter-website-bot]

Visit the preview URL for this PR (updated for commit 1448e24):

https://flutter-docs-prod--pr12559-feat-migrate-injected-dartp-5hje0crv.web.app

[parlough]

Thanks for applying this here as well!