Add argv parsing example

[ivan-kleshnin]

Hey guys, can I suggest an example of argv (CLI) parsing?

1) NodeJS provides process.argv obviously but it's quite low-level. For example, I'd like to have

$ node argv.js foo -f bar

parsed as

["foo", ["f", true], "bar"]

instead of

["foo", "-f", "bar"]

You may also want to parse argv-like strings in Browser (to highlight code or whatever).

2) Moreover, this example showcases a parsing of quoted strings:

string: function() {
  // one of possible quotes, then sequence of anything except that quote (unless escaped), then the same quote
  return P.oneOf(`"'`).chain(function(q) {
    return P.alt(
      P.regex(new RegExp(`[^\\\\${q}]+`)),
      P.string(`\\`).then(P.any)
    )
      .many()
      .tie()
      .skip(P.string(q));
  });
}

with escape support, which no other example currently does (except json.js but not 100% close).

Any remarks are welcome. I followed the style of other examples – it passes $ npm run lint.

[coveralls]

Coverage remained the same at 100.0% when pulling 715c5a7 on ivan-kleshnin:master into 13359d7 on jneen:master.

[wavebeem]

This is a pretty cool idea. I literally never thought to use Parsimmon for this.

If you don't mind addressing these comments I'd be happy to merge this in :)

[wavebeem]

I think it might make more sense to take the entire options string as argv[2] like node cli.js "--foo --qux=guz -b" to show that this is parsing out one whole string and not relying on the shell (bash, etc) to parse for us.

[wavebeem]

this regexp is pretty confusing to me. i think you might be able to rewrite this using some of the other parsimmon constructors?

you could also just write two separate string rules and then use alt() to combine them

[ivan-kleshnin]

Yes, double escaping is going on here, not the cleanest code in the history :)
I agree with both points – will try to rewrite this as you suggested.

[ivan-kleshnin]

Can't find out, why Linter complains on this:

option: function(r) {
  return P.seq(
    P.alt(
      P.string("-").then(P.regex(/[a-z]/)),
      P.string("--").then(r.word)
    ),
    P.alt(
      P.string("=").then(r.word),
      P.of(true)
    )
  );
},

and wants me to change it to less readable this:

option: function(r) {
  return P.seq(
    P.alt(P.string("-").then(P.regex(/[a-z]/)), P.string("--").then(r.word)),
    P.alt(P.string("=").then(r.word),P.of(true))
  );
},

To clarify

Direct run with $ eslint examples/argv.js shows no warnings but $ npm run lint crashes without any clue:

> parsimmon@1.7.1 lint /Users/ivankleshnin/Sandboxes/parsimmon-fork
> prettier --list-different '{examples,src,test}/**/*.js' webpack.config.js && eslint examples src test webpack.config.js

examples/argv.js
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! parsimmon@1.7.1 lint: `prettier --list-different '{examples,src,test}/**/*.js' webpack.config.js && eslint examples src test webpack.config.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the parsimmon@1.7.1 lint script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/ivankleshnin/.npm/_logs/2018-03-26T09_19_57_051Z-debug.log

until I run $ npm run lint:fix. Any idea why this may happen?

[wavebeem]

The full command behind npm run lint:fix is prettier --list-different '{examples,src,test}/**/*.js' webpack.config.js && eslint examples src test webpack.config.js

The problem is Prettier wants to reformat those lines. If alt(...) took an array instead I think it would format them how you want.

I think if you use a.or(b) instead of P.alt(a, b) Prettier may format this more how you like.

It might also be worth checking out if a newer version of Prettier formats that nicer.

[ivan-kleshnin]

It might also be worth checking out if a newer version of Prettier formats that nicer.

I checked and unfortunately no. v1.11 improved one minor thing in comparison to 1.7 in this code but not that one.

If alt(...) took an array instead I think it would format them how you want.

Tried this:

alt(...[
  ___
])

and also no. It wants me to fold an array into a single line...

I personally never use such tools – the're always too stupid and unable to pick normal cases.
But, your project – your rules, I left the code layout as this thing wants.

[wavebeem]

Looks great now. Thanks for the contribution @ivan-kleshnin!

[ivan-kleshnin]

No problem. Thank you for such a great library!