parseAsTuple

[tacomanator]

There have been a few situations where this would be useful, so I wanted to suggest it.

For example, a date range parser could be implemented as:

parseAsTuple([parseAsIsoDate, parseAsIsoDate])

Advantages over parseAsArrayOf(parseAsDate):

1. Ensures both dates are present.
2. Resulting type of [string, string] instead of string[] prevents certain type errors.
3. Elements could have different types (not relevant in this example).

Just an example there are obviously many others.

[franky47]

That's a good idea, would you like to open a PR?

I like the tuple approach, as it's not as opinionated as a range (where terminology of min/max, from/to, start/end, left/right etc would get in the way), and not potentially fixed to two values (a ?coordinates=12.34;56.78;9 could make sense for a 3D coordinate system encoded into a single search param)

Elements could have different types (not relevant in this example).

That also makes sense, in the example above (map coordinates), the 3rd coordinate (zoom) is generally an integer while the other ones are floats (with different constraints on values). This can be reflected in the type, but also in the kind of serialisation/deserialisation being done.

The implementation should likely:

• Accept between 2 and 8 parsers (there are limitations in variadic generics in TypeScript IIRC, 8 seems like a good upper bound)
• Allow specifying a separator character (see parseAsArrayOf for inspiration wrt/ encoding occurrences of the separator in the values before joining). This could be an optional second argument after the array of parsers.
• Fail parsing if any of the sub-parsers fail

Edit: upgrading this discussion to an issue for tracking: #1022.