Mahmood Ali af2e2bc7ed cli: sequence cli.Ui operations ...

Fixes a bug where if a command flag parsing errors, the resulting error
and help usage messages get interleaved in unexpected and non-user
friendly way.

The reason is that we have flag parsing library effectively writes to
ui.Error in a goroutine.  This is problematic: first, we lose the sequencing between help
usage and error message; second, cli.Ui methods are not concurrent safe.

Here, we introduce a custom error writer that buffers result and calls
ui.Error() in the write method and in the same goroutine.

For context, we need to wrap ui.Error because it's line-oriented, while
flags library expects a io.Writer which is bytes oriented.

2019-12-16 10:08:17 -05:00

12 KiB

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