Ignoring overflow

The only two widgets that throw this error are Flex (Row / Column) and UnconstrainedBox, the former is obviously the most common.

The problem is not actually the fault of the Flex itself, rather the constraints given by its parent. In order to solve this issue the main axis constraint needs to either be unbounded i.e. have a maximum main axis size of double.infinity or have a clipBehavior of Clip.none.

The simplest way to ignore overflow is to use Flex instead, and set the clip:

Flex(
  direction: Axis.horizontal,
  clipBehavior: Clip.none,
  children: [
    Some(), Long(), Widgets(),
  ],
)

Or using OverflowBox:

OverflowBox(
  maxWidth: double.infinity,
  child: Row(children: [
    Some(), Long(), Widgets(),
  ]),
)

I’ve seen some people use Wrap to achieve a similar result, I highly discourage that because the fact that Wrap doesn’t check for overflow is probably an oversight and may change in the future.