Improved Lambda Argument Handling

[amadeus]

This is a first pass at adding back in the jsArrowFuncArgs matching when using parenthesis.

It should mostly fix issues specified at #378 and #364.

I have been using the following test file to ensure syntax highlighting seems to work, I would be open to more test cases to add to this to ensure things are working.

/* eslint vars-on-top:0 */
function test1({size = 'big', cords = { x: 0, y: 0 }, radius = 25} = {}) {
    console.log(size, cords, radius);
}

var test2 = function(test2arg = () => {
    return true;
}) {

};

var test3 = function(){};

var test4 = (test4arg, { test4arg2 = 2 }) => {};

test3((arg) => {
    var test5 = (test5arg) => {
    };
});

test3((test6arg = 2 + 2, { test6arg2: x, test6arg3: y }) => {
});

test3((test7arg) => {});

test3(test8arg => {});

var test9 = function(x, y){
    var tub = () => {};
};

var test10 = (test10arg, /* test comment */ test10arg2 = () => {}) => {};

var test11 = {};

test3.then(
    (result) => {
        var test12 = (test12arg = { test12arg2: [] }) => {};
        this.send(result);
    }
);

test3('_.blind()', () => {});

test3((test13arg, test13arg2) => test4.exists(test13arg, (test14arg) => {
    return true;
}));

// Checking syntax highlighting on the line before this, should be empty

We don't handle this file perfectly, but we do breakdown 'gracefully' (meaning we do not show error parenthesis groups).

Current issues I haven't been able to figure out:

• How to handle parenthesis inside the jsArrowFuncArgs match
• Handle a multiline version of jsArrowFuncArgs

I have done a bit of research into other editors like Sublime and Atom, and none can even handle this file completely correctly, and they ALL break with the 2 issues I mentioned above (at least their default syntax highlighting, I never explored plugins that may do things better).

[davidchambers]

Nice work, @amadeus! I'm pleased to see how minimal the changes are.

[amadeus]

I've gone ahead and push a copy of this branch to this repo, so it's easier for you guys to test:

https://github.com/pangloss/vim-javascript/tree/lambda-experiments

[alexlafroscia]

@amadeus I tried out that branch, it fixed some issues I was seeing around highlighting getting messed up when using "fat arrow" functions, in cases where the parameters are surrounded in parenthesis. Stuff like this:

myFunction((foo) => {
  return foo.bar;
});

Where the ) on the last line would be highlighted in bright red, as if it was an error.

Thanks for the fix!