FlexLayout doesn't measure out to full height when placed inside ScrollView

[PureWeen]

Description

If you have a FlexLayout inside a ScrollView the FlexLayout will only ever measure to the height of the ScrollView

        <ScrollView Grid.Row="1" HeightRequest="300">
            <FlexLayout
                Direction="Row"
                Wrap="Wrap"
                AlignItems="Center"
                AlignContent="Center"
                BindableLayout.ItemsSource="{Binding Items}"
                BindableLayout.ItemTemplate="{StaticResource ColorItemTemplate}" />
        </ScrollView>

If you replace the FlexLayout with a StackLayout then you're able to Scroll.

Steps to Reproduce

ScrollViewFlex.zip

1. run project
2. you should be able to scroll up and down and see more squares
3. if you switch to a StackLayout then it's scrollable

Version with bug

Preview 11

Last version that worked well

Unknown/Other

Affected platforms

iOS, Android, Windows, macOS

Affected platform versions

All of them

Did you find any workaround?

If you set an explicit height on the FlexLayout then you can scroll the FlexLayout

Relevant log output

No response

[chris-ux]

Alternatively, when not in ScrollView, the height of the FlexLayout grows "infinitely", seemingly unaware of the height of its content. Submitted issue: #3852

[v-xiaofchen]

Verified repro with windows and the above project.