On variable drill down, inherited fields are not visible

[vsmenon]

In the variables window here, this is of type PageController. When I expand, I see fields defined directly in that class. I don't see fields inherited from the superclass, ScrollController (e.g., _initialScrollOffset or keepScrollOffset):

This is with:

> flutter --version
Flutter 2.0.1 • channel stable • https://github.com/flutter/flutter.git
Framework • revision c5a4b4029c (3 days ago) • 2021-03-04 09:47:48 -0800
Engine • revision 40441def69
Tools • Dart 2.12.0

FYI - @annagrin @grouma - not sure how pervasive this is, but I think fairly high priority if so.

[vsmenon]

This is one level up in the stack. In this case, this is a subclass of State, and I similarly cannot see fields from State:

https://github.com/flutter/flutter/blob/e5322acc77f116803c93cfe1d538ae3c16a19423/packages/flutter/lib/src/widgets/framework.dart#L884

[annagrin]

I don't see the same outcome - I wonder if this is could be related to dart-lang/sdk#45266.
I am currently working on the fix.

[annagrin]

I created a smaller repro - apparently evaluation works fine, but local variables returned from dwds do not contain inherited fields - note that watch window and expression evaluation box evaluate b.t but it does not appear in local variables view.

We currently use ddc runtime function sdk_utils.getFields to get the fields of the object (this in code below), and it does not seem to list all the inherited properties. Note the comment: // TODO(alanknight): Handle superclass fields.:

webdev/dwds/lib/src/debugging/instance.dart

Line 276 in 51ad9e7

final fieldNameExpression = '''function() {

Suggestion:

• Add getting all fields functionality to the ddc runtime
• Add a more concise way for a debugger to ask for fields of an object
• If possible, it should use dart evaluation instead of js evaluation
  • Can we create dart ddc runtime library that the debugger can use?
  • Another option could be reflection but it seems that dart:mirrors are not supported on flutter and I am not sure it works on web: Allow using dart:mirrors flutter/flutter#1150

code example:

class A {
  A(this.t);
  int t;
}

class B extends A {
  B(this.p): super(p+1);
  int p;

  void foo() {
    print('in foo');
  }
}

void main() {

  B b = B(0);
  A a = A(42);

  b.foo();
}

[annagrin]

This thread is now split into the following two issues, closing as duplicate:

• [frontend_server] Expression evaluation is broken after hot restart when debugging flutter code sdk#45266
• [dev_compiler] Support showing inherited fields in the debugger sdk#45387