Flyout doesn't size to its content if no width/height is set in first child component

[lyahdav]

Environment

1. npx react-native --version: 4.13.0
2. npx react-native run-windows --info:

  System:
    OS: Windows 10 10.0.19041
    CPU: (40) x64 Intel(R) Xeon(R) Gold 6248 CPU @ 2.50GHz
    Memory: 157.00 GB / 190.60 GB
  Binaries:
    Node: 12.18.3 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.17.0-20190429.1820 - C:\open\fbsource\xplat\third-party\yarn\yarn.BAT
    npm: 6.14.6 - C:\Program Files\nodejs\npm.CMD
    Watchman: 20200724.030019 - C:\tools\watchman\watchman.EXE
  Installed UWP SDKs:
    10.0.18362.0

3. reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock
    AllowDevelopmentWithoutDevLicense    REG_DWORD    0x1
    AllowAllTrustedApps    REG_DWORD    0x1

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

1. Run playground win32 app
2. Go to Flyout example
3. Change the code so that no width/height is set on the Flyout's child View

Expected Results

Expected: Flyout width/height is set automatically based on the size of its children.
Actual: Flyout size is set based on where the Flyout is present in the view hierarchy outside of the Flyout.

On Mac we fixed this by correctly resetting the shadow layout context:

@implementation PopoverShadowView

- (CGSize)contentSize {
  // There should only be one child.
  RCTShadowView* childShadowView = self.reactSubviews.firstObject;
  return childShadowView ? childShadowView.layoutMetrics.frame.size : CGSizeZero;
}

- (void)layoutSubviewsWithContext:(RCTLayoutContext)layoutContext {
  for (RCTShadowView* childShadowView in self.reactSubviews) {
    layoutContext.absolutePosition = CGPointZero;

    [childShadowView
        layoutWithMinimumSize:CGSizeZero
                  maximumSize:CGSizeMake(INFINITY, INFINITY)
              layoutDirection:RCTUIKitLayoutDirectionFromYogaLayoutDirection(self.direction)
                layoutContext:layoutContext];
  }
}

@end

[lyahdav]

Note I found a quick workaround: add a position: absolution style to the first child view in Flyout.

[asklar]

Could be an issue with the flyout viewmanager not setting the constraints properly. CC @kmelmon in case this looks familiar?
Putting in backlog as it isn't blocking right now.

[chrisglein]

Not something we plan to address on the Paper renderer as we move towards Fabric. The equivalent component for Fabric is tracked here.