Complex Type Use

[robcxyz]

Complex Type Use

Using complex types has issues

• Proposal Status: wip

• Issue Number: 228

• Proposal Doc: complex-type-use.md

Overview

Currently we allow declaring types for fields within a declarative hook and can have those fields validated when the hook is called but can't create fields which are validated on assignment. This prevents creation of typed data types like list[str] or list[Foo] within a hook.

Examples

F<-:

  foo: list

()<-:

  try_ok->: F --foo string --try --except ok

  ok->: F --foo ['string']

This is fine.

F<-:

  foo: str

G<-:

  foo: int

H<-:

  bar:

    type: list[F]

<-:

  exec:

    # Technically not a list[F] but F into a list

    ok->: F --foo {{item}} --for ['a','b']

    try_ok->: G --foo {{item}} --for ['a'] --try --except ok

    # This is right

    h_ok:

      ->: H

      bar:

        - foo: bar

    h_try_ok:

      ->: H --try --except ok

      bar:

        - not foo: bar

#ok:

#- foo: a

#- foo: b

#try_ok:

#- ok

#h_ok:

#  bar:

#  - foo: bar

#h_try_ok: ok

These are the only ways to instantiate a list[F] with the first ways a hack, instantiating F into a list.

F<-:

  foo: str

G<-:

  bar:

    type: dict[str, F]

<-:

  exec:

    ok:

      ->: G

      bar:

        a:

          foo: bar

    ok_merge:

      ->: G --merge

      bar:

        a:

          foo: bar

    try_ok:

      ->: G --try --except ok

      bar:

        a:

          not foo: bar

#ok:

#  bar:

#    a:

#      foo: bar

#bar:

#  a:

#    foo: bar

#try_ok: ok

Only way to do it with dict[str, F] is with an intermediary object.

There is no way to get rid of that intermediary object's key - bar in this case. For instance there is no way to achieve this output

F<-:

  foo: str

G<-:

  bar:

    type: dict[str, F]

<-:

  exec:

    ok_merge:

      ->: G --merge

      bar:

        a:

          foo: bar

#ok_merge:

#  a:

#    foo: bar

Instantiating Large Objects

T<-:

  # Some large thing

  foo: bar

data:

  # Some large thing

  foo: baz

call_bad:

  ->: T --foo {{data.foo}} # ... Won't scale.