Support space as the delimiter for long arguments

[josegonzalez]

Most cli tools I use have a space character to delimit the flag and it's option, and it would be cool to be able to do so for pflag. I realize this would be yet another departure from the flag stdlib, but it would definitely be cool to have.

I tried just changing https://github.com/ogier/pflag/blob/master/flag.go#L429 to a space character, but it seems I'll also need to change something in FlagSet, just not sure where. Would be happy to make a PR adding another method that configures this and make the requisite changes given some direction :)

[ogier]

I'm worried that this will make boolean arguments ambiguous. For example, does the following set the bar flag to false, or does it set the bar flag to true with one positional argument?

foo --bar false

Also #16 is a request to make arguments for any long argument optional, which I think makes sense, but would make parsing any long flag without an = ambiguous.

In the end, the main spec pflag follows when deciding how to parse flags is http://www.gnu.org/software/libc/manual/html_node/Argument-Syntax.html which doesn't allow long options without an = sign.

[ncw]

Actually flag does allow long options with a space. Here is an example on the playground.

The standard GNU getopt_long also accepts --flag argument, try this for an example

ls --sort extension

The docs you linked to above is the document for getopt_long - it may be that the = convention is a POSIX thing only.

The flag package ignores arguments for bool options. Here is a demo on the playground, so --bar is the same as -bar=true and -bar true just treats true as another argument.

So I think it would be more standards compliant (both with flag and getopt_long) to make pflag allow space as the delimiter with long arguments.

PS thanks for a great package - I'm using it in rclone.

[josegonzalez]

Looks like this is implemented in the spf13 fork. I switched to that for now.

[ncw]

@josegonzalez thanks for the heads up - I'm going to investigate.