Implemented autosave on a 5-second timer

[Levi-Lesches]

Fixes #2871 by saving the editor content to local storage under they key user_input every 5 seconds, and in dispose

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[Levi-Lesches]

@parlough I fixed the double quotes

[parlough]

Sweet! Thanks so much for implementing this again :D

[parlough]

Do you think it's worth it to convert this fallback to a callback, so we don't unnecessarily retrieve the old snippet?

[Levi-Lesches]

I think ?? is short circuiting, so it should be fine? EDIT: Just checked, it is

[Levi-Lesches]

Oh, if you meant not retrieving the old snippet or user input in case a gist id or otherwise is provided.

I tried making it a callback, and got some very strange errors on the web side. Each time I restarted, it was that JS can't read some property, but it was a different property each time. Once it didn't even let the flutter tool connect because the bootstrapper got stuck. Not sure what's up with that but I'll leave the PR as-is for now

[Levi-Lesches]

@parlough I Implemented this in the latest set of commits. I think there was something wrong with my Flutter installation last time I was working on this. Just upgraded to 3.27.0 with no issues.

[Levi-Lesches]

@parlough Any updates?

[Levi-Lesches]

Sorry for the annoying pings, just want to make sure this doesn't slip between the cracks

[parlough]

@Levi-Lesches Sorry for the delay, I've been away.

The change looks good to me, but before landing, we need to wait for others to determine DartPad's storage policies and how we will inform users of them.

I'll land this PR when able and ping you if any changes are needed.

Thanks again!

[Levi-Lesches]

Hi @parlough, any updates?

[johnpryan]

We added a cookie banner now (#3097), so we should be OK to use local storage.

[Levi-Lesches]

I'm trying to add an integration test that tests:

• entering text really does save content to the local storage
• loading the page results in the local storage text being displayed, unless
• if the page is loaded with a Gist, checks that the Gist is loaded instead of the local storage

This will complicate CI a bit, so I'm updating the README with instructions from the Flutter docs.

[Levi-Lesches]

I ended up going with unit tests instead as I couldn't get the integration tests to work: WidgetTester.enterText(String) calls WidgetTester.showKeyboard(), which requires an EditableText widget somewhere in the subtree, but the current setup with CodeMirror forwards keyboard input directly to the CodeMirror library without using Flutter's TextInput.

The test cases above are still tested, though, so I'm ready for another review.

EDIT ...okay, now I'm ready. I didn't add tests for:

• Fallback shows when a Gist has no main.dart file, because the flutterdevrelgists account has no such gist
• Flutter sample ID takes precedence, because I didn't want the tests to break when Flutter docs change