provide some kind of defaultDecode as a fallback for decoder option

[seansfkelley]

I ran into an issue recently where I wanted to parse out boolean values to a proper boolean type:

const PARSE_OPTIONS = {
  decoder: value => {
    if (value === 'false') {
      return false;
    } else if (value === 'true') {
      return true;
    } else {
      return value;
    }
  }
};

Turns out this breaks parsing of URI-encoded array types:

> qs.parse("foo%5B%5D=bar", {});
{ "foo": [ "bar" ] }

> qs.parse("foo%5B%5D=bar", PARSE_OPTIONS);
{ "foo%5B%5D": "bar" }

Which I guess is reasonable (though, aside, the decoder API is not well-documented and has a lot of tricky subtleties like this). I wanted the last branch to just "do the default thing", but unfortunately that option is not available to me, so I'm stuck choosing between explicitly importing the private utils file and hoping it doesn't change or move, or re-implementing the default and hoping it doesn't change (which it looks like it might).

Providing a default implementation, even for this simple function, would make this use-case much more robust.

[ljharb]

One possibility might be changing the encoder/decoder calls to pass the default encoder/decoder as the second argument to the function - although that might be breaking if anyone's checking arguments.length.

[seansfkelley]

I would be okay with that solution as well. It'd keep everything in one place, too.