TS's new node ESM support

Will need work on our side to integrate.

microsoft/TypeScript#44501
weswigham/TypeScript#67

Roughly

adds new module: node12 and module: nodeNext configs
In them:

existing extensions obey package.json "type" field
new extensions .mts, .mjs, .cts, .cjs force one or the other; ignore package.json "type" field

Questions I still have

Are any of the above assumed to be modules without needing to add export {};?

With 4.5 beta announced 2 weeks ago, and the final on the horizon, time for us to do something.

@alvis

@alvis are you referring to a pull request that you have submitted?

@alvis

I've assigned this to @alvis and added it to our next milestone. Let us know if you need any guidance to implement the necessary changes. I've added some notes below.

At a minimum, you'll need to add require.extensions hooks for mts, mjs, cts, and cjs extensions. You may also need to add them to the extensions passed to createResolve:

ts-node/src/esm.ts

Lines 50 to 54 in 3b40365

    
           // Custom implementation that considers additional file extensions and automatically adds file extensions 
        
           const nodeResolveImplementation = createResolve({ 
        
             ...getExtensions(tsNodeService.config), 
        
             preferTsExts: tsNodeService.options.preferTsExts, 
        
           });

ts-node/src/index.ts

Lines 482 to 491 in 3b40365

    
           export function getExtensions(config: _ts.ParsedCommandLine) { 
        
             const tsExtensions = ['.ts']; 
        
             const jsExtensions = []; 
        
             // Enable additional extensions when JSX or `allowJs` is enabled. 
        
             if (config.options.jsx) tsExtensions.push('.tsx'); 
        
             if (config.options.allowJs) jsExtensions.push('.js'); 
        
             if (config.options.jsx && config.options.allowJs) jsExtensions.push('.jsx'); 
        
             return { tsExtensions, jsExtensions }; 
        
           }

Should the new extensions be enabled conditionally, only when your TS version is >= 4.5?

I don't expect you'll need to implement any fancy resolving logic beyond that. TS already handles resolving within the typechecker, and node's existing resolution logic should continue to behave.

Will this mean that we can now potentially have import { foo } from './foo', basically omitting the extensions just like in commonJS ?

@PodaruDragos

@PodaruDragos you're probably looking for node's --experimental-specifier-resolution=node which we already support. Just as node requires you to pass that flag, we also require you to pass that flag, often via the NODE_OPTIONS environment variable.

https://nodejs.org/dist/latest-v17.x/docs/api/esm.html#customizing-esm-specifier-resolution-algorithm

Add the ability to run TypeScript files from CLI

Update dependency ts-node to v10.8.0 (#1367)

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TS's new node ESM support #1414

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	// Custom implementation that considers additional file extensions and automatically adds file extensions
	const nodeResolveImplementation = createResolve({
	...getExtensions(tsNodeService.config),
	preferTsExts: tsNodeService.options.preferTsExts,
	});

	export function getExtensions(config: _ts.ParsedCommandLine) {
	const tsExtensions = ['.ts'];
	const jsExtensions = [];

	// Enable additional extensions when JSX or `allowJs` is enabled.
	if (config.options.jsx) tsExtensions.push('.tsx');
	if (config.options.allowJs) jsExtensions.push('.js');
	if (config.options.jsx && config.options.allowJs) jsExtensions.push('.jsx');
	return { tsExtensions, jsExtensions };
	}

TS's new node ESM support #1414

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Roughly

Questions I still have

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alvis commented on Oct 17, 2021

cspotcode commented on Oct 17, 2021

cspotcode commented on Oct 18, 2021

PodaruDragos commented on Dec 11, 2021

cspotcode commented on Dec 11, 2021

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