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squabble Command Line Argument Parser

Fuck... why the hell would you make another one?

Why not another one? Frankly, I could not find a good library to handle attached short options (e.g., in gcc where the argument can appear with the option without any delimiting space or character: -DFOO=BAR). The rest is just personal preference.

If you're looking for something a bit more full featured, I would suggest yargs, which approaches the problem similarly and is pirate themed. The yargs module includes things like online help and usage, but notably does not support attached short options unless the value is numeric. I found similar issues with minimist. Of special note is optimist which is quite popular, but has been deprecated and replaced with yargs.

The other arg parsing modules I found have drastically different APIs, make large assumptions, and some were poorly tested or documented; they all had something which precluded their use.

Minimal

The squabble module doesn't provide a lot of micro-settings to exactly configure the parser, but hopefully provides just enough sensible settings to serve most purposes with minimal fuss.

Unassuming

Besides the couple of options available, the parser makes very few assumptions about the way you want your arguments parsed. If you don't want args beginning with a hyphen to be treated as options, that's cool. If you like Windows-style options, squabble doesn't have you covered, but it also doesn't get in your way.

Flexible

Even though there are not many settings or a complicated API, squabble still manages to provide some flexibility through the match function, which can match by regular expression and invoke a custom handler. Several of the squabble functions are just wrappers around the match function with a handler that performs additional parsing. This could be used to add java or Windows style options, if you wish (but keep in mind, java style won't play nicely with the shortOpts method).

How's This Shit Work?

The most straightforward example is to create a parser and call its parse method. By default, it will use the args from process.argv.slice(2). You can also pass an array of args instead. In any case, the default parser will simply return a result containing the provided arguments.

var parser = require("squabble").createParser(),
    args;

// parse global process arguments
args = parser.parse();

// parse specified arguments
args = parser.parse(["-a", "--foo", "Hey", "You"]);
assert(args[0] === "-a");
assert(args[1] === "--foo");
assert(args[2] === "Hey");
assert(args[3] === "You");

That's not actually useful at all

The default parser isn't very useful. Calling a few methods on the parser before parsing will enable some useful auto-magic. The shortOpts method will enable single letter flags prefixed by a single hyphen, longOpts will enable arbitrarily-long options prefixed by a double hyphen. Finally, the stopper method will enable the "--" option terminator.

// really?  hmm... if you want some automagic, try this
var parser = require("squabble").createParser()
        .shortOpts()
        .longOpts()
        .stopper(),
    args = parser.parse(["-a", "--foo", "Hey", "You", "--", "--bar"]);

assert(args[0] === "You");
assert(args[1] == "--bar");
assert(args.named["-a"] === true);
assert(args.named["--foo"] === "Hey");

I'd like some long options with no argument, like `--all`

The shortOpts and longOpts methods are useful to quickly start parsing, but by default, short options do not accept an argument, and long options do. Long options are also OK with not having an argument if one isn't present. For any particular argument, you can use the flag or option method to reject or accept arguments, respectively. Any named argument defined in this manner will be set to false if the argument was not specified.

var parser = require("squabble").createParser()
        .option("-o")
        .flag("-x")
        .flag("--all"),
    args = parser.parse(["--all", "file.foo", "-o", "output.txt"]);

assert(args[0] === "file.foo");
assert(args.named["--all"] === true);
assert(args.named["-o"] === "output.txt");
assert(args.named["-x"] === false);

How do I handle extra verbosity, like -vvv?

You can have the parser return a count of the number of times an argument was passed, if you prefer. Just use the count method on the parser before parsing. You must also specify shortOpts if you want to combine them all into one argument. Without shortOpts, "-v -v -v" would be needed to do the same thing.

var parser = require("squabble").createParser()
        .shortOpts()
        .count("-v"),
    args = parser.parse(["-vvv"]);

assert(args.named["-v"] === 3);

Can I mix that with --verbose somehow?

For any of the methods which define a named argument, you can specify more than one name and they will all act as aliases for one another.

var parser = require("squabble").createParser()
        .shortOpts()
        .count("-v", "--verbose"),
    args = parser.parse(["-vv", "--verbose"]);

assert(args.named["-v"] === 3);
assert(args.named["--verbose"] === 3);

How do you enable attached short option arguments?

Any time you use the shortOpts method, any explicitly defined short option which needs an argument will also permit that argument to be attached to the option.

var parser = require("squabble").createParser()
        .shortOpts()
        .option("-I"),
    args = parser.parse(["-I/home/me/src/headers"]);

assert(args.named["-I"] === "/home/me/src/headers");

The `gcc` -I option actually allows any number of arguments

True 'dat. The list method handles that situation.

var parser = require("squabble").createParser()
        .shortOpts(
        .list("-I"),
    args = parser.parser(["-I/path", "-I/other/path"]);

assert(args.named["-I"][0] === "/path");
assert(args.named["-I"][1] === "/other/path");

What about positional arguments?

If you have positional arguments which must always be present, you can assign a name to that position to let squabble handle it with the required method.

var parser = require("squabble").createParser()
        .required("METHOD")
        .required("URL")
        .shortOpts(),
    args = parser.parse(["-x", "GET", "example.com"]);

assert(args.named["-x"] === true);
assert(args.named["METHOD"] === "GET");
assert(args.named["URL"] === "example.com");

What if I want an optional positional argument

You can do that, too, with the optional method. The order of optional args is maintained, but the position of the optional arguments in relation to the required arguments is determined at the time the FIRST optional argument is added. This means you can have any number of named optional args, but they must appear contiguously together between any required arguments.

var parser = require("squabble").createParser()
        .required("FOO")
        .optional("BAR")
        .required("BAZ")
        .optional("BIFF"),
    args = parser.parse(["apple", "banana", "carrot", "date"]);

// Note: even though BAZ comes before BIFF in definition, BIFF comes right
// after the previous optional argument BAR, and so comes first during parsing
assert(args.named.FOO === "apple");
assert(args.named.BAR === "banana");
assert(args.named.BAZ === "date");
assert(args.named.BIFF === "carrot");

// but if an argument is removed, BIFF is the one which misses a value
args = parser.parse(["apple", "banana", "carrot"];
assert(args.named.FOO === "apple");
assert(args.named.BAR === "banana");
assert(args.named.BAZ === "carrot");
assert(args.named.BIFF === false);

Can I set a default besides `false`?

Yeah, with the aptly named default method. This works on any named argument, including short opts and long opts. If you use name aliases, you need to set the default for each alias.

var parser = require("squabble").createParser()
        .option("-t", "--tmpdir")
        .default("-t", "--tmpdir", "/tmp"),
    args = parser.parse([]);

assert(args.named["-t"] === "/tmp");
assert(args.named["--tmpdir"] === "/tmp");

What if I want X to do Y with Zs?

That's what rule is for. Provide a string or RegExp to match args against (exact string matches are always matched first) and a parse function which is called when a matching argument is encountered. The parse function receives the current result so far, the remaining arguments after the current one, and the current argument value.

There are a couple ways to use this. The shortOpts method matches anything beginning with a hyphen (which is not explicitly defined), breaks them up into multiple single letter options, and unshifts those back onto the args so they can be re-parsed as separate arguments. The longOpts does something similar.

Another example might be the GNU-ism where the "-" argument can be used in place of a filename to mean STDIN. The following code snippet handles that.

var parser = require("squabble").createParser(),
    args;

// unused callback parameters include args and arg.
parser.rule("-", function(result) {
    result.push(process.stdin);
});

args = parser.parse(["-"]);
assert(args[0] === process.stdin);

What's next?

The following is a list of enhancements expected to be added to squabble in the near future.

strict/loose to throw errors for undefined options
optionType to define simple option parse rules
refactor shortOpts and longOpts into modules using optionType
posixOpts, gnuOpts, javaOpts, winOpts modules
extend default with shortcut methods such as parser.default.option("-v", "--verbose", 0)