glideapps/quicktype

Detect and properly handle recursive types

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#273 opened on Nov 14, 2017

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 (3 comments) (0 reactions) (0 assignees)TypeScript (10,867 stars) (968 forks)batch import
Elmbuggood first issue

Description

Recursive types can result even from JSON input (via merging of similar types - see the recursive.json sample), so every backend either needs to be able to handle them, or signal that it can't. Some languages, like Swift, require an option to handle them, so we'd either have to turn that option on when recursive types are involved, or only allow merging in case the option is on. It would be even better if we had an analysis that could detect not only whether there are recursive types, but which types are involved in the recursion, which would allow us to generate class types only for them in Swift, for example, or emit forward declarations in C++.

Contributor guide

Tech stack
typescript
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understand recursive type definitionsFamiliarity with quicktype's codebaseKnowledge of type generation backends
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Examine the existing type inference logic in src/TypeGraph.ts and src/TypeBuilder.ts. Understand how merging works and where recursive types arise. Review the Swift backend (src/Swift.ts) to see how the 'recursive' option is handled. Propose a strategy to detect recursion and either generate class types for Swift or forward declarations for C++. Discuss with maintainers on the issue thread.