`moduleType` is not actually a valid config field (unlike `moduleTypes`)

[dPowNextdoor]

Summary

In the website, ReadMe, and other docs, it says moduleType: Override the module type of certain files, ignoring the package.json "type" field. See "Module type overrides" for details.. However moduleType is an internal-only field, not to be used by the tsconfig.json's ts-node field.

Expected Behavior

Any field listed in the website, ReadMe, etc. to be usable.

Actual Behavior

This field (to my knowledge, please correct me if I'm wrong) doesn't do anything. moduleTypes (emphasis on the trailing s) does.

Steps to reproduce the problem

Look through the source code linked above.

Alternatively, don't set type: module in package.json, import some CJS file into your TS file, and then change the tsconfig.json given below from

// no errors
"moduleType": "esm",
"moduleTypes": {
    "**/*.mjs": "esm",
    "**/*.cjs": "cjs"
}

to

// lots of errors
"moduleTypes": {
    "**/*.js": "esm",
    "**/*.mjs": "esm",
    "**/*.cjs": "cjs"
}

and watch ts-node collapse.

Specifications

• ts-node version: v10.4.0 (latest)
• node version: v16.13.2
• TypeScript version: v4.6.0-dev.20220204 (though tested on 4.5.4 and 4.5.5 as well)
• tsconfig.json, if you're using one:

{
    "compilerOptions": {
        "target": "ESNext",
        "lib": [
            "ESNext",
            "DOM",
            "DOM.Iterable"
        ],
        "module": "ESNext",
        "moduleResolution": "node",
        "strict": true,
        "jsx": "react-jsx",
        "allowJs": true,
        "esModuleInterop": true,
        "allowSyntheticDefaultImports": true,
        "experimentalDecorators": true,
        "emitDecoratorMetadata": true,
        "resolveJsonModule": true,
        "forceConsistentCasingInFileNames": true,
        "newLine": "lf",
        "preserveSymlinks": false,
        "incremental": true,
        "isolatedModules": true,
        "outDir": "dist",
        "declaration": true,
        "declarationDir": "dist/types",
        "baseUrl": ".",
        "paths": {
            "@/*": [ "src/*" ],
            "/*": [ "*" ]
        }
    },
    "include": [
        "./src/**/*"
    ],
    "exclude": [
        "./node_modules",
        "dist"
    ],



    "ts-node": {
        "require": [
            "tsconfig-paths/register"
        ],
        "preferTsExts": true,
        "experimentalReplAwait": true,
        "transpileOnly": true,
        "moduleType": "esm", // Field in question
        "moduleTypes": {
            "**/*.mjs": "esm",
            "**/*.cjs": "cjs"
        },
        "compilerOptions": {
            "module": "nodenext",
            "isolatedModules": false
        },
        "include": [
            "./**/*"
        ]
    }
}

• Operating system and version: Mac (Big Sur 11.6.1), Linux (Mint Uma)

Related

Maybe this is part of the experimental phase of ts-node, but I had assumed moduleType: "esm" would feign setting type: module in package.json, but clearly it does not. In fact, it doesn't appear to do anything.

Suggested Fix

Either fix (what I assume to be) the typo in the docs, or (preferably) make moduleType do as it currently says it does and override type in package.json.

[cspotcode]

Is this a typo, a missing "s"?

[cspotcode]

Fixed by #1633

The docs on this page are correct: https://typestrong.org/ts-node/docs/module-type-overrides

See also: #1007 which explains the best way to take advantage of our native ESM support.

[dPowNextdoor]

Thanks @cspotcode! I know this was very minor, but I went down a rabbit hole, confused why moduleType wasn't working. I appreciate the fix (and how quickly it was made)!

[cspotcode]

The valid options are also described in the official schema. Some editors can pick this up and assist you.

https://www.schemastore.org/json/