pathToRegexp returns array with extra elements when used with optional path parts

[esaborg]

Keys array returned form pathToRegexp has unexpected entries when path has optional parts.

const { regexp, keys } = pathToRegexp(`/:one/:two/:three`);
// keys: (as exptected)
// [
//    { type: 'param', name: 'one' },
//    { type: 'param', name: 'two' },
//    { type: 'param', name: 'three' }
//  ]

When one part is changed to optional, keys array unexpectedly grows. I'd expect both cases to return keys array with 3 entries.

const { regexp, keys } = pathToRegexp(`/:one{/:two}/:three`);
// keys:
// [
//    { type: 'param', name: 'one' },
//    { type: 'param', name: 'two' },
//    { type: 'param', name: 'three' },
//    { type: 'param', name: 'one' },
//    { type: 'param', name: 'three' }
//  ]

[blakeembrey]

This is by design, the keys match the result of the regexp. I can open a PR to document this but I'd recommend using match instead.

[mxngls]

@blakeembrey would you mind elaborating on the imperative behind that design decision? As a user this seems quite unintuitive. A more ergonomic API instead, might be to include the optional parameter with it's proper type i.e group and the remaning parameters thus only once. Currently keys can be a wildcard or a parameter, but there's no indication of which parameters might be optional. The naive approach would be parsing the array of keys and look for repeated keys to infer which keys might be optional. This seems quite error prone to be honest.