FlagUsagesWrapped stops wrapping the rest of a usage string after a word wider than the description column

[mahnerak]

When a usage string contains a word too wide to fit the remaining space, wrapN returns the entire rest of the string unwrapped — not just the over-wide word. Everything after it lands on one long line.

flag.go, in wrapN:

w := strings.LastIndexAny(s[:i], " \t\n")
if w <= 0 {
      return s, ""   // <- gives up on the whole remainder, not just this word
}

Reproducer (similar to apptainer/apptainer#3668 )

package main

import (
      "fmt"

      "github.com/spf13/pflag"
)

func main() {
      fs := pflag.NewFlagSet("example", pflag.ContinueOnError)
      fs.String("mount", "", "a mount specification e.g. 'type=bind,source=/opt,destination=/hostopt'. The rethis description is never wrapped.")
      fmt.Print(fs.FlagUsagesWrapped(60))
}

Actual — the second line is 116 columns:

      --mount string   a mount specification e.g.
                       'type=bind,source=/opt,destination=/hostopt'. The rest of this description is never wrapped.

Expected — the unbreakable word overflows on a line of its own, and wrapping resumes:

      --mount string   a mount specification e.g.
                       'type=bind,source=/opt,destination=/hostopt'.
                       The rest of this description is
                       never wrapped.

I'll try to draft a quick PR, but before that would like @spf13 to confirm we agree on the "Expected" behavior.

[AzazelSensei]

Opened #503