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Description

Bug Report

🔎 Search Terms

emitDecoratorMetadata require
emitDecoratorMetadata import

🕗 Version & Regression Information

This is the behavior in every version I tried, and I reviewed the FAQ for entries about 3.3.3, 4.1.3

⏯ Playground Link

Playground link with relevant code

💻 Code

import * as vscode from 'vscode';

function LogMethod(
  target: any,
  propertyKey: string | symbol,
  descriptor: PropertyDescriptor
) {
  console.log(target);
  console.log(propertyKey);
  console.log(descriptor);
}

class Demo {
  @LogMethod
  public foo(bar: vscode.Memento) {
    // do nothing
  }
}

const demo = new Demo();

🙁 Actual behavior

The output contains const vscode = __importStar(require("vscode")); when emitDecoratorMetadata: true but not when emitDecoratorMetadata: false

🙂 Expected behavior

As the type of bar as nothing to do with the compiled JS, the import of vscode should not exist regardless of the value of emitDecoratorMetadata

Contributor guide

Research direction: Investigate the TypeScript compiler's handling of emitDecoratorMetadata and its impact on import elision. Focus on the transformer that processes decorators and how it preserves type only imports when metadata is emitted.
Tech stack: typescript
Domain: toolingbuild system
Issue type: Bug
Difficulty: 2
Estimated time: Half day
Activity status: Stale
Clarity: Clear
Prerequisites: TypeScriptDecorators
Newbie friendliness: 30