[Issue 9260] New: getopt should allow setting booleans to false

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=9260

           Summary: getopt should allow setting booleans to false
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Phobos
        AssignedTo: nobody at puremagic.com
        ReportedBy: andrej.mitrovich at gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2013-01-02 19:12:04 PST ---
import std.getopt;
void main(string[] args)
{
    bool b;
    getopt(args, "b", &b);
}

If you pass:

$ rdmd test.d --b=true

The '=true' is skipped, as getopt only cares whether '--b' is present. The
problem is that this leads to a user thinking that the opposite works:

$ rdmd test.d --b=false

However 'b' is still true in this case, the '=false' part is discarded.

The documentation *does* mention that booleans can only be set to on, however
it only uses the syntax '--b' and never mentions '--b=true' (it might be an
oversight allowing it). To avoid confusion and avoid code breakage, we should
either:

1) Throw when syntax '--b=false' is used, because it has no effect
2) Implement --b=false

I think #2 would be the best choice here.

The current alternative is to use enums, ala:

enum B { no, yes }
import std.getopt;
void main(string[] args)
{
    B b;
    getopt(args, "b", &b);
}

$ rdmd test.d --b=no

But there should be no problem implementing #2.

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