sveltejs/svelte-preprocess

Variables created with Pug/Svelte mixin +each are not recognized by Typescript

Open

#207 opened on Jul 31, 2020

View on GitHub
 (6 comments) (1 reaction) (0 assignees)TypeScript (150 forks)auto 404
bughelp wanted

Repository metrics

Stars
 (1,798 stars)
PR merge metrics
 (PR metrics pending)

Description

Problem

Variables created with Pug/Svelte mixin (i.e. +each('links as link')) are not recognized by Typescript analyzer and cause "Cannot find name 'link'. Did you mean 'links'?" error.

Imgur

Example code:

<template lang="pug">
ul.nav
  +each('links as link')
    li(class:active="{ link.active }")
      a(href!="{ link.link }") { link.title }
</template>

<script lang="ts">
interface Link {
  active: boolean 
  link: string
  title: string
}

let links: Link[] = [
  { active: false, link: '#', title: 'Test Link 1' }, 
  { active: false, link: '#', title: 'Test Link 2' }, 
  { active: false, link: '#', title: 'Test Link 3' }, 
]
</script>

Context

Editor: VS Code or NVim Used preprocessors: Typescript, Pug, Sass. svelte-preprocess version: 4.0.9

Contributor guide

Research direction
Investigate how the preprocessor handles Pug mixins in Svelte files. Look at the relevant parsing code in svelte preprocess to understand why variables defined via mixins are not recognized by TypeScript. Consider how the `+each` mixin is transformed and whether the variable scope is correctly propagated to the TypeScript analysis.
Tech stack
typescript
Domain
frontend
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
SveltePugTypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70