argument parsing: make -- argument terminate parsing

[StefanKarpinski]

See discussion here: https://groups.google.com/forum/#!topic/julia-users/lahbdoIImcQ

When parsing options to julia encountering a -- argument should terminate option parsing and treat the rest of the arguments as simply part of ARGS.

[jsbee]

any update on this?

[jakebolewski]

-- now terminates argument parsing, but the example highlighted in the google groups issue stil does not work because julia loads foo.jl with arguments bar & baz but then tries to load bar as a source file and fails because bar does not exist. One way to fix this would be to disallow loading a script -L foo.jl and running an additional source file at the same time.

julia -i -L foo.jl -- bar baz

disallowing

julia -i --load=foo.jl source.jl arg1 arg2

[StefanKarpinski]

Perhaps the -i flag should be what forces interactive mode and thus causes arguments to be considered as arguments rather than scripts. Alternately, the -- could signal that everything after it should go verbatim in ARGS – implying that they are not the names of scripts to be loaded.

[jakebolewski]

The second option will not work because julia --longarg foo -- src.jl is a valid way to write julia --longarg=foo src.jl using getopt style parsing.

[StefanKarpinski]

Says who? Don't we get to dictate what the -- means for parsing options and arguments to julia?

[jakebolewski]

Unfortunately no if we are using the system getopt library (which we are currently). julia just see's the argument buffer that is left over from command line parsing.

[StefanKarpinski]

Ok, that's annoying, but it also seems reasonable to me that -i should force arguments to go into ARGS instead of being used as scripts. Currently julia script.jl and julia -i script.jl behave the same way except that isinteractive() is false in the former and true in the latter. Might as well make the -i flag a little more useful than that.

[jakebolewski]

--load doesn't really have to exist. Is it just to save a toplevel require("src.jl") call in a source file?

[tkelman]

Might as well make the -i flag a little more useful than that.

While I agree that the -i flag currently doesn't serve a whole lot of purpose, encouraging its use more places is not necessarily a good thing... Running a script with -i can easily stop and block for user input, because that's an entirely reasonable thing to do in some places when isinteractive() is true.

[StefanKarpinski]

How about scanning the arguments for -- before even passing them to getopt? That way we're not subject to what getopt thinks that -- should mean, but we can rely on getopt for the rest of the option parsing.