This module should not be used in runtime. Instead, use a transformer during compilation. about typescript-is HOT 10 CLOSED

I ran into this issue again. I found that if I added:

globals: {
    "ts-jest": {
      compiler: "ttypescript"
    }
  }

...to my jest.config.js file, the issue went away.

from typescript-is.

I'm still getting this error running npm start

Error: This module should not be used in runtime. Instead, use a transformer during compilation.

My package.json:

{
  "scripts": {
     "start": "ts-node-dev --compiler ttypescript --respawn src/index.ts"
  },
  "dependencies": {
    "typescript": "^3.8.3"
  },
  "devDependencies": {
    "ts-node-dev": "^1.0.0-pre.44",
    "ttypescript": "^1.5.10",
    "typescript-is": "^0.15.0"
  }
}

My tsconfig.json:

{
  "compilerOptions": {
    "plugins": [
      { "transform": "typescript-is/lib/transform-inline/transformer" }
    ],
    "target": "es5",
    "module": "commonjs",
    "strict": true,
    "esModuleInterop": true,
    "forceConsistentCasingInFileNames": true
  }
}

from typescript-is.

I'm also seeing this error message on a new Node project. The verbose flag confirms the plugin is running (I get typescript-is: transforming program with 287 source files; using TypeScript 4.2.4.), but then still receive This module should not be used in runtime. Instead, use a transformer during compilation at runtime. Not sure if I'm missing something or something is broken.

I've tried npx ttsc, ts-node-dev --compiler typescript, and both of those as my npm run build command; in both cases I get the same result (verbose message that the files are being transformed but a "Module should not be used at runtime" error.

package.json:

{
  "scripts": {
    "lint": "eslint . --ext .ts",
    "build": "npm run lint && npx ttsc",
    "serve": " firebase use develop && npm run build && firebase emulators:start --only auth,functions,firestore",
    "deploy": "firebase deploy --only functions",
    "test": "env TS_NODE_COMPILER_OPTIONS='{\"module\": \"commonjs\" }' mocha -r ts-node/register 'test/tests/**/*.ts'"
  },
  "engines": {
    "node": "12"
  },
  "main": "lib/index.js",
  "dependencies": {
    ...
    "reflect-metadata": "^0.1.13",
    "typescript-is": "^0.18.2"
  },
  "devDependencies": {
    ...
    "ts-node": "^9.1.1",
    "ts-node-dev": "^1.1.6",
    "ttypescript": "^1.5.12",
    "typescript": "^4.2.4"
  },
  "private": true
}

tsconfig.json:

{
  "compilerOptions": {
    "baseUrl": "./src",
    "module": "commonjs",
    "noImplicitReturns": true,
    "noUnusedLocals": true,
    "allowJs": false,
    "outDir": "lib",
    "sourceMap": true,
    "strict": true,
    "target": "es2017",
    "forceConsistentCasingInFileNames": true,
    "plugins": [
      {
        "transform": "typescript-is/lib/transform-inline/transformer",
        "verbose": true,
      },
    ]
  },
  "include": [
    "src/**/*",
  ],
  "compileOnSave": true,
}

from typescript-is.

hi @jtremback

The error you mentioned only happens when the transformer from typescript-is is not used. The default implementation is to throw a run-time error.
I'm not exactly sure why the transformer is not used, but as you mentioned that removing the --transpileOnly flag resolved the issue, I'm guessing that this option causes ts-node-dev to skip the transformation part.
Digging a bit further into ts-node-dev this option sounds like it causes the compiler to strip out the type checking part and just emit JS code. That would definitely prevent typescript-is from transforming the code and generating type guards, because it needs the type information to do this.

I hope this clarifies the situation. There is not much I can do if the entire type checking part of compilation is skipped.

Is there anything else you'd like to have clarified?

Thanks!

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Closing for housekeeping purposes.

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Thanks @woutervh- !

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I got this same error when trying to run jest tests. I added the plugins section to my tsconfig.json, but perhaps ts-jest is somehow overriding those settings?!?

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Hi @mtiller

I'm not sure how ts-jest runs the compiler. Sounds like there should be some configuration in ts-jest to enable ttypescript or vice versa. Maybe there is some info on these two repos about how to do it.

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@mtiller Thank you for sharing!!

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Any solution for this? Still running into it

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