Add BiDiLensSpec defaulted with factory method

[krissrex]

I would appreciate a defaulted which is re-evaluated every time, so I can use e.g. Instant.now(), LocalDate.now() etc.

I currently do this:

val datetime = Query.localDate(DateTimeFormatter.ISO_LOCAL_DATE)
        .optional(
            "date",
            description = "A date for something"
        )

// Usage
val foo = datetime(req) ?: LocalDate.now(DEFAULT_ZONE)

And would appreciate if I could do this:

val datetime = Query.localDate(DateTimeFormatter.ISO_LOCAL_DATE)
        .defaulted(
            "date",
            { LocalDate.now(DEFAULT_ZONE) },
            description = "A date for something"
        )

// Usage
val foo = datetime(req)

The name does not need to be defaulted, if this collides with existing signatures. Other names could be: defaultedLazy (I don't want it lazy, it's active/recompute every time), defaultFactory, defaultedWithFactory, defaultedComputed, computeDefault, etc..

---

I tried adding the functionality in my own codebase, but I failed because paramMeta was private, and get and set as well, so extension functions on BiDiLensSpec or inheritance of BiDiLens didn't quickly solve my problem.

[krissrex]

Label: feature request

[dzappold]

Have you tried to use a Lens as second parameter?
I guess it could look similar to Lens(myMeta) { _ -> LocalTime.now() }

[krissrex]

Have you tried to use a Lens as second parameter? I guess it could look similar to Lens(myMeta) { _ -> LocalTime.now() }

Yes, but I might have done it wrong. I struggled with the constructor, because I couldn't create a Meta object.
I looked at the official defaulted, which did:

        defaulted(name, Lens(Meta(false, location, paramMeta, name, description)) { default }, description)

, but I dont have access to location and paramMeta when I want to create myMeta.

  Query.instant().defaulted("start", Lens(meta = ???, { _ -> Instant.now() }))

The source code isn't obvious either, so I have no clue what location and meta are, and if I can construct them myself easily, or what data should even go into them. If you have any advice, I would appreciate it.

[krissrex]

It seems the location and paramMeta come from the Query object, so something like this?

  Query.instant()
      .defaulted(
          "start",
          Lens(
              meta =
                  Meta(
                      required = false,
                      location = Query.location,
                      paramMeta = ParamMeta.StringParam,
                      name = "start",
                      description = "My description of start"),
              { _ -> Instant.now() }))

Quite verbose compared to e.g. a Query.instant().defaultFactory("start", { Instant.now() })

[daviddenton]

I've made the defaulted mechanism take a LensExtractor (Request) -> T and made it a fun interface, so you can now do: ```
Query.int().defaulted("foo", { 123 })

Will be out in the next version