[Bug]: Incorrect print result of TSModuleDeclaration

[qbx2]

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

import parser from "@babel/parser";
import generator from "@babel/generator";

const generate = generator.default;

const ast = parser.parse(`module MyModule {
  export function myFunction(): void {
    console.log("Hello, world!");
  }
}`, {
  sourceType: "module",
  plugins: [
    "jsx",
    "typescript",
  ],
  ranges: false,
});

console.log(generate(ast).code);

Configuration file name

No response

Configuration

No response

Current and expected behavior

Current behavior:

namespace MyModule {
  export function myFunction(): void {
    console.log("Hello, world!");
  }
}

Expected behavior:

module MyModule {
  export function myFunction(): void {
    console.log("Hello, world!");
  }
}

Environment

System:
OS: macOS 14.1.1
Binaries:
Node: 18.17.0 - ~/Library/Caches/fnm_multishells/19593_1715933137130/bin/node
Yarn: 1.22.17 - /opt/homebrew/bin/yarn
npm: 9.6.7 - ~/Library/Caches/fnm_multishells/19593_1715933137130/bin/npm
pnpm: 8.13.1 - ~/Library/Caches/fnm_multishells/19593_1715933137130/bin/pnpm
npmPackages:
@babel/generator: ^7.24.5 => 7.24.5
@babel/parser: ^7.24.5 => 7.24.5
@babel/types: ^7.24.5 => 7.24.5

Possible solution

No response

Additional context

No response

[babel-bot]

Hey @qbx2! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

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[nicolo-ribaudo]

The two syntaxes are equivalent (like choosing to use single vs double quotes in strings), and module is deprecated. I think Babel should keep the current behaviour.

[qbx2]

@nicolo-ribaudo In old TypeScript, you might be right. However in the latest TypeScript, 'module' is not deprecated and different from namespace.

[qbx2]

From https://www.typescriptlang.org/docs/handbook/namespaces.html ,

A note about terminology: It’s important to note that in TypeScript 1.5, the nomenclature has changed. “Internal modules” are now “namespaces”. “External modules” are now simply “modules”, as to align with ECMAScript 2015’s terminology, (namely that module X { is equivalent to the now-preferred namespace X {).

This post outlines the various ways to organize your code using namespaces (previously “internal modules”) in TypeScript. As we alluded in our note about terminology, “internal modules” are now referred to as “namespaces”. Additionally, anywhere the module keyword was used when declaring an internal module, the namespace keyword can and should be used instead. This avoids confusing new users by overloading them with similarly named terms.

It seems that you’re talking that ’internal module’ is deprecated but I’m talking that babel rewrites ‘external module’ to ‘namespace (internal module)’

[qbx2]

The difference of two is: ‘module’ won’t be shared across files. Unlike ‘module’, ‘namespace’ can be shared across files if the name is equivalent. Therefore, it can lead to a name conflict to rewrite module to namespace.

[nicolo-ribaudo]

"external modules" are when you write import/export at the top level of the file, not the code you are showing (which is an internal module).

From the docs you quoted: "(namely that module X { is equivalent to the now-preferred namespace X {)."

[qbx2]

@nicolo-ribaudo Oh, there was my misunderstanding. Thank you for the clarification.