Microsoft/TypeScript

Trailing comma in dynamic import should be allowed also when used in a `typeof` type

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#61,489 opened on Mar 26, 2025

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 (1 comment) (2 reactions) (0 assignees)TypeScript (6,726 forks)batch import
Domain: ES ModulesHelp WantedPossible Improvement

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Description

🔎 Search Terms

trailing comma dynamic import

🕗 Version & Regression Information

  • This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEBbA9sArhBAiAZs5W8A3gL4BQZYyAdgM4Au8AbvALzxQDuUAloz4gAOyGPQAUufFgA0ASgDcZegE9BCACpt4KtchzwBw0RLwE5iyjQbMATFq69+QkeMlnS5pao132OkHoGzsZuMh4KZEA

💻 Code

declare module "foo" {}

const v = await import("foo",);
type T = typeof import("foo",);

const v2 = await import("foo",{},);
type T2 = typeof import("foo",{},);

🙁 Actual behavior

The trailing commas in the type-level import()s are reported as syntax error

🙂 Expected behavior

The syntax of import() at the type-level should match the one at the value level, thus allowing trailing commas.

Additional information about the issue

Note that the error was correct before import attributes, but import attributes changed the dynamic import syntax to allow trailing commas.

Contributor guide

Research direction
Inspect the parser for type level import() and add support for trailing commas, mirroring the value level import() syntax.
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.
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.
75