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I have a TypeScript project, based on Node.js, with several modules (using workspaces). Everything executes correctly, but I’m still receiving warnings. In particular, when running this (as a package.json ‘script’ in Yarn)

ts-node --project path/tsconfig.json path/script.ts <args-to-script>

I’m seeing two classes of warnings:

  • In Visual Studio Code, squiggly underlines in the imports of makefont.ts, because I (have to) specify .ts file extensions;
  • At the command-prompt, warning messages on execution, stating that “ExperimentalWarning: Type Stripping is an experimental feature and might change at any time”

I think the two warnings are related. I’m using NodeJS 23.7.0, Yarn 1.22.22, ts-node 10.9.2, TypeScript 5.5.4

Imports with file extensions:

"import { glyphs } from 'fonts/font1.ts' // squiggly underline!"

Without the .ts, I get “Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/Users/andrew/projects/retrofabulationzx/app/node_modules/fonts/font1' imported from /Users/andrew/projects/retrofabulationzx/app/rom/build/makefont.ts”

Note that, additionally, I’ve had to split off a type import (Glyph) into a separate import statement. I suspect that both of these issues are related to the ‘Type Stripping’ mentioned below:

ExperimentalWarning

It seems that ts-node is using the (experimental) Node Type Stripping feature to run TypeScript… I am sure that it wasn’t doing this previously, before I implemented workspaces…

Does ts-node have problems running within a Yarn/NPM ‘workspace’?

What the project looks like:

  • fonts/ (workspace)
    • font1.ts
    • package.json
    • tsconfig.json
  • rom/ (workspace)
    • build/
      • makefont.ts
      • tsconfig.json
    • generated/ (output directory)
    • package.json
  • package.json
  • tsconfig.json

/package.json

{
    "private": true,
    "workspaces": [
        "fonts",
        "rom",
    ],
    "devDependencies": {
        "@jest/globals": "^29.1.2",
        "@types/node": "^22.4.0",
        "ts-jest": "^29.1.2",
        "ts-node": "^10.9.2",
        "typescript": "^5.5.4"
    },
    "packageManager": "[email protected]"
}

/tsconfig.json

{
    "compilerOptions": {
        "target": "es6",
        "module": "ES6",
        "outDir": "dist",
        "esModuleInterop": true,
        "moduleResolution": "node"
    },
    "include": [],
    "exclude": [ "**/node_modules" ],
}

fonts/package.json

{
    "name": "fonts",
    "version": "1.0.0",
    "type": "module"
}

fonts/tsconfig.json

{
    "extends": "../tsconfig.json",
    "compilerOptions": {
        "composite": true
    },
    "include": [ "./*.ts" ]
}

rom/package.json

{
    "name": "rom",
    "version": "1.0.0",
    "type": "module",
    "devDependencies": {
        "@types/node": "^22.4.0",
        "fonts": "1.0.0",
        "ts-node": "^10.9.2",
        "typescript": "^5.5.4",
        "zxsys": "1.0.0"
    },
    "scripts": {
        "genfont": "ts-node --project build/tsconfig.json build/makefont.ts generated/font.z80",
        // plus others
    }
}

rom/build/tsconfig.json

{
    "extends": "../../tsconfig.json",
    "ts-node": {
        "esm": true
    },
    "compilerOptions": {
    },
    "references": [
        { "path": "../../fonts" },
        // +others
    ],
    "include": [ "./*.ts" ],
}

Exact command-line invocation

yarn workspace rom genfont
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    " I can provide " - you need to, this is specific to your case. You don't have to specify extensions if ts is properly configured. What is "fonts"? A package from the workspace? You need to structure it in a way this allows imports from inside the package. "Type Stripping" is node feature, not ts-node, this means that ts files weren't processed by ts Commented Feb 5 at 11:20
  • @EstusFlask, Thanks, (I didn’t want to clutter up the question with too much stuff!) Have added all the relevant file contents, I think. That was my thought: that the file was not being processed by the TS compiler, but it’s definitely being invoked via ts-node. Commented Feb 6 at 9:08
  • 1
    Since ts-node calls node inside, this warning is what happens when node executes .ts directly, also notice that ts-node is abandoned and can add another layer of its own problems. In my experience this structure of ts-only monorepo projects results in troubles. Try to alias "fonts" in "rom" with compilerOptions-paths config (not references-path as you did), e.g. see "@foo/shared/*": ["../foo-shared/src/*"] entry here stackoverflow.com/questions/75403735 , this way it's expected that you could import it like "fonts/font1" Commented Feb 7 at 12:40

1 Answer 1

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The reason seems to be the use of ES Modules. By the look of things, when ESM are used, ts-node simply falls back to calling node, which is why you get these warnings. Disabling esm in the ts-node config and changing the type to commonjs in my "package.json" files helped in my case.

However, this isn't ideal. A quick Google search suggests that ES Modules are the future. At the same time, after taking a quick look at ts-node's code, it seems to be deliberately skipping type checks for ES Modules (https://github.com/TypeStrong/ts-node/blob/main/esm/transpile-only.mjs). So, you either get ES Modules, or type checking - but not both. I'm new to TypeScript and node.js, and would really appreciate a better solution.

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1 Comment

Yes… My eventual ‘solution’ was switching from Node to Deno :) It works really smoothly and made my TypeScript problems go away!

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