josdejong/ducktype

Are recursive types supported?

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#40 opened on Jan 17, 2021

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enhancementhelp wanted

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Description

Is it possible to define a type e.g. "segment" that is either a string, a number, or an array of segments (recursive definition)? If not, please consider it a feature request.

Something like:

const segment = ducktype.indirect();
segment.that = ducktype(String, Number, [segment]);

or even:

const segment = ducktype.recursive(self => ducktype(String, Number, [self]));

Basically I need to validate that all "leaves" of a non-flat array are of a particular union type. I cannot flatten the array before validating because it is nested in a bigger data structure that I want to validate as a whole (as opposed to picking these arrays out of it for flattening and validation), and the nesting structure within the array is meaningful.

Contributor guide

Research direction
Investigate how other validation libraries (e.g., Zod, Yup) support recursive types. Evaluate possible syntaxes for ducktype and implement a prototype.
Tech stack
javascript
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60