Dartpad support

[dcharkes]

The Flutter API docs use dartdoc tools to render DartPad on the website:

• https://github.com/flutter/flutter/blob/fe0bacbacfab6b67473c0e4c174a047f7da21682/dartdoc_options.yaml#L13-L15
• https://github.com/flutter/flutter/blob/20dd20932dc87d14be4bc04f12a1a1f755b73e8a/packages/flutter/lib/src/material/app_bar.dart#L127-L132
• https://github.com/flutter/flutter/tree/master/dev/snippets

However, dartdoc tools are not rendered on pub.dev (and in the IDE). This makes it impossible to dartdoc tools for packages.

We should consider adding first-class support for dartpad in dartdoc.

(I'm pretty sure we've discussed this before, but I can't find a tracking issue.)

[sigurdm]

The biggest obstacle I think is that dartpad (last I checked) still works with a fixed set of packages - so it would only work for documenting those packages.

[srawlins]

#3503 "Implement Flutter's @tool snippet natively" can be considered a parent issue for this issue.

You are right, @sigurdm that supporting dartpad generally does support only a limited number of customers, but I still think it's an important feature; I have long wanted to implement it but it never quite made it above the prioritization bar. The main benefits I can think of are:

1. Simplifying generating docs for the Flutter SDK and the Dart SDK, by avoiding the complicated @tool logic.
2. Improving the performance of generating docs for Flutter in particular, which makes much use of @tool snippet (or @tool sample? I forget). Not shelling out to a different dart process hundreds of times.
3. Many flutter favorite packages can make use at pub.dev, like maybe provider, riverpod, some top plugins, and some core packages like path, collection, etc. Whoever is available at dartpad.
4. Any package developer who publishes their docs on their own server can conceivably make use of it, if they also host their own dartpad instance, and we make the directive configurable. This is maybe a long shot, but there could be great ROI if we do have some important package authors doing this, or enterprise package authors who host their own pub service and dartpad.

[sigurdm]

Sure - don't get me wrong - I think embedding dartpad everywhere would be super-cool and we absolutely should do it.

And I don't think even think it is unlikely we can make dartpad resolve most packages.