Editing value on provider throws eval error

[kenzieschmoll]

Repro steps:

1. run the flutter gallery app
2. Click the "Reply" app from the carousel of apps at the top of the flutter gallery homescreen
3. On the provider page of DevTools, the EmailStore provider will become available
4. try to edit the _count field

@rrousselGit @jacob314

[rrousselGit]

Oh, I found the problem.

It's because EmailStore is defined as:

class EmailStore with ChangeNotifier

rather than:

class EmailStore extends ChangeNotifier

That messes up with the informations about where _count is coming from.

With mixins, _count's Instance.owner is

Instance(name: _EmailStore&Object&ChangeNotifier, uri: package:gallery/studies/reply/model/email_store.dart)

rather than:

Instance(name: ChangeNotifier, uri: package:flutter/.../foundation.dart)

That's a problem because since it is a private property, the eval needs to use the library that defines the property for the mutation to work.
But with mixins, vm_service gives an incorrect uri.

So it's behaving as if email_store.dart tried to update _count instead of as if flutter/foundation.dart tried to update it. But the former is not legal, hence the error.

I don't think this can be fixed. At least not without vm_service giving us the correct uri.

[rrousselGit]

Mixins also are a source of problem with #3006 / #3004 by the way, for the same reasons.

#3006 relies on checking whether the property's owner URI matches with the name of the inspected application.
But since with mixins, ChangeNotifier._count is said to be defined by the class that mixes-in ChangeNotifier, then the property is not considered as "defined by a dependency", so it is visible.

[jacob314]

Until we get the mixin issues sorted out how about we disable edits on private properties to be safe. I'd also be happy with disabling edits on all properties by default and only showing it as "experimental: edit property values" in the settings page.

[kenzieschmoll]

Seeing this issue again with a different use case. Here I am trying to edit the _value of a ValueNotifier field

doing so yields this error:

Repro steps:

1. run DevTools (A) on the web (this is the test app) *pro tip: change this to light theme so there is no confusion about which app is the debugger and which app is being debugged.
2. Connect this instance of DevTools to an arbitrary flutter app (this is so that the PerformanceController will show up in the list of providers).
3. run another instance of DevTools (B)(desktop or web, whichever you prefer).
4. Connect this DevTools to the DevTools web app (A) you launched in step 1).
5. Navigate to the provider page in DevTools (B). You should see the PerformanceController in the list of providers. Try to change the value of the matchIndex notifier as the screenshot shows.

[elliette]

Now that the Provider panel is a DevTools extension, I'm closing this issue in favor of rrousselGit/provider#883.