josdejong/mathjs

TS regression: Narrowing of MathNodes by type

Open

#2,810 opened on Oct 13, 2022

View on GitHub
 (23 comments) (0 reactions) (0 assignees)JavaScript (1,298 forks)batch import
bughelp wantedtypescript

Repository metrics

Stars
 (13,832 stars)
PR merge metrics
 (No merged PRs in 30d)

Description

Describe the bug Prior to v11.3 (not sure how far back, but certainly at least 10), MathNode would be narrowed based on its type property:

const doStuffWithMathNode(node: MathNode) => {
  if (node.type === 'FunctionAssignmentNode) {
    // now TS knows that node is a FunctionAssignmentNode and lets you access associated props
    // like node.params
  }
  // back to being a wider MathNode
}

To Reproduce

Contributor guide

Research direction
Investigate the changes between v11.2 and v11.3 that affected type narrowing for MathNode. Look at the type definitions for MathNode and its subtypes to restore proper narrowing.
Tech stack
typescript
Domain
tooling
Issue type
Bug
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.
1-3 hours
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
TypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70