Microsoft/TypeScript

Comments on constructor super call not preserved in ES5 unless it has additional empty line

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#49,045 opened on May 10, 2022

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Domain: Comment EmitExperience EnhancementHelp WantedSuggestion

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Description

Bug Report

🔎 Search Terms

  • comments
  • stripped
  • super
  • constructor

🕗 Version & Regression Information

  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about _________

⏯ Playground Link

Playground link with relevant code

💻 Code

class B {
    constructor(...args: any[]) {}
}

class A extends B {
    constructor(...args: any[]) {
        /** this comment is not preserved */
        super(...args)
    }
}

class C extends B {
    constructor(...args: any[]) {
        /** this comment is preserved */
        
        super(...args)
    }
}

🙁 Actual behavior

Comment on the super call was not preserved in the ES5 output

🙂 Expected behavior

Comment on the super call to be preserved

Contributor guide

Research direction
Inspect the TypeScript emitter's handling of comments on constructor super calls, particularly the logic that determines whether to emit comments before 'super'. Look at the emit flow for class constructors and how blank lines affect comment preservation.
Tech stack
typescript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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
TypeScriptunderstanding of AST/emitter
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60