Use field_name?: field_type for optional fields, instead of OneOf extension, see #5

[dpup]

Hello @seanami,

The tests passed without any changes, which is reassuring. Here's what the
generated code looks like:

With emit_unpopulated=true

export type OptionalFieldsResponse = {
  emptyStr: string
  emptyNumber: number
  emptyMsg: OptionalFieldsSubMsg | null
  emptyOptStr?: string
  emptyOptNumber?: number
  emptyOptMsg?: OptionalFieldsSubMsg | null
  zeroStr: string
  zeroNumber: number
  zeroMsg: OptionalFieldsSubMsg | null
  zeroOptStr?: string
  zeroOptNumber?: number
  zeroOptMsg?: OptionalFieldsSubMsg
  definedStr: string
  definedNumber: number
  definedMsg: OptionalFieldsSubMsg | null
  definedOptStr?: string
  definedOptNumber?: number
  definedOptMsg?: OptionalFieldsSubMsg | null
}

export type OptionalFieldsSubMsg = {
  str: string
  optStr?: string
}

And with emit_unpopulated=false:

export type OptionalFieldsResponse = {
  emptyStr?: string
  emptyNumber?: number
  emptyMsg?: OptionalFieldsSubMsg
  emptyOptStr?: string
  emptyOptNumber?: number
  emptyOptMsg?: OptionalFieldsSubMsg
  zeroStr?: string
  zeroNumber?: number
  zeroMsg?: OptionalFieldsSubMsg
  zeroOptStr?: string
  zeroOptNumber?: number
  zeroOptMsg?: OptionalFieldsSubMsg
  definedStr?: string
  definedNumber?: number
  definedMsg?: OptionalFieldsSubMsg
  definedOptStr?: string
  definedOptNumber?: number
  definedOptMsg?: OptionalFieldsSubMsg
}

export type OptionalFieldsSubMsg = {
  str?: string
  optStr?: string
}

Please review the following commits I made in branch dan/optional-again:

7444de9 (2024-04-26 16:07:33 -0700)
Use field_name?: field_type for optional fields, instead of OneOf extension, see #5

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• Code is easy to understand and conforms to style guides
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[seanami]

Nice! 👍 It's encouraging how easy this was to modify. I think this is the way. The IsOneOf for optional fields seems like an internal implementation detail anyway, and it's not necessary for TypeScript's type system anyway. This will make the resulting TS types much nicer to work with in editors.