ts-node gives type errors, presumably doesn't load .d.ts file, when allowJs && checkJs

Expected Behavior

Code compiles.

Actual Behavior

Gives type error, saying variable implicitly has an any type.

Steps to reproduce the problem

Create a library with type declarations:

// foo.js
export function foo({ foo }) {
   console.log(`Inside foo({foo:${foo}})`);
}
// foo.d.ts
export declare function foo({ foo }: {
   foo: number;
}): void;
// package.json
{
  "name": "foo",
  "version": "1.0.0",
  "main": "foo.js",
  "types": "foo.d.ts",
  "type": "module",
  "license": "MIT"
}

Create a TS project, set allowJs, checkJs to true.
import the library and call foo({foo:100})
Run tsc, it compiles without any error.
Run node --loader ts-node/esm main.ts

Output:

TSError: ⨯ Unable to compile TypeScript:
../myapp-foo/foo.js:1:23 - error TS7031: Binding element 'foo' implicitly has an 'any' type.

1 export function foo({ foo }) {

Minimal reproduction

https://github.com/itsfarseen/ts-node-repro

Specifications

ts-node v10.1.0
node v16.5.0
compiler v4.3.5

tsconfig.json: https://github.com/itsfarseen/ts-node-repro/blob/main/myapp-bar/tsconfig.json

Operating system and version: Arch Linux

Might need to adjust ts-node's ignore option to ignore myapp-foo or enable ts-node's files option.

I read in the FAQ that I need to fiddle with --files option to make ts-node read global types.
But here there are two separate packages. myapp-bar has myapp-foo in the dependencies section of its package.json.

Does anyone know why allowJs and checkJs make a difference though?
It makes sense that when checkJs is false, typechecking the JS files are skipped.
But why doesn't it give errors when allowJs is false? Does the presence of .d.ts files make the JS file equivalent to a TS file for typechecking?
Then why are they not considered equivalent when allowJs and checkJs are both true?

@itsfarseen

@itsfarseen I think this error is unfortunately valid. The problem isn't within myapp-bar, but in myapp-foo since you enabled checkJs. Note the file that is erroring, it is not part of tsc when you run it. If you do run tsc, with the same configuration in myapp-foo, you'll see that same error.

As for solutions, I don't have a good one right now. In theory the scope option should be used to avoid this problem but I wasn't able to get it working right now.

Edit: To clarify it's not related to files or type resolution or anything else, just due to literally applying the tsconfig.json on a JavaScript file you didn't expect.

Update: I was using the scope option wrong (trying to give it a directory instead of a boolean). This works for me:

TS_NODE_SCOPE=true node --loader ts-node/esm main.ts

You can also add this to your tsconfig.json too:

"ts-node": {
  "scope": true
}

@blakeembrey

@blakeembrey could you explain what is happening under the hood when checkJs is enabled?

I'm not really an expert on TypeScript when it comes to the JS features, but based on this I believe it's basically doing type-checking on your JavaScript (almost) as if it's TypeScript.

Whenever you require a file and ts-node needs to compile it, the file is manually added to the "files" array as needed to ensure TypeScript looks at it and emits compiled code. I suspect this is happening: tsc will not look at the .js file because it has instead resolved to the .d.ts file. ts-node, on the other hand, has seen a require() which resolved to the js file, so it has forced the .js file to be included in your "files" array. tsc --listFiles will show the files pulled into compilation. tsc --traceResolutions will explain why they are pulled into compilation. *Above, "files" array refers to the array in tsconfig.json

…

On Mon, Aug 9, 2021, 1:50 AM Blake Embrey ***@***.***> wrote: I'm not really an expert on TypeScript when it comes to the JS features, but based on this <https://www.typescriptlang.org/docs/handbook/intro-to-js-ts.html> I believe it's basically doing type-checking on your JavaScript (almost) as if it's TypeScript. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#1421 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAC35OA3MJBHWY273PE5AL3T35UD7ANCNFSM5BXNYTRQ> .

As far as I can tell, this has been solved so I'm going to close it. Please comment if the issue persists and if you think it's a ts-node bug.

Navigation Menu

Repository navigation

ts-node gives type errors, presumably doesn't load .d.ts file, when allowJs && checkJs #1421

Expected Behavior

Actual Behavior

Steps to reproduce the problem

Minimal reproduction

Specifications

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

ts-node gives type errors, presumably doesn't load .d.ts file, when allowJs && checkJs #1421

Description

Expected Behavior

Actual Behavior

Steps to reproduce the problem

Minimal reproduction

Specifications

Activity

cspotcode commented on Aug 7, 2021

itsfarseen commented on Aug 8, 2021

blakeembrey commented on Aug 9, 2021

blakeembrey commented on Aug 9, 2021

itsfarseen commented on Aug 9, 2021

blakeembrey commented on Aug 9, 2021

cspotcode commented on Aug 9, 2021

cspotcode commented on Oct 6, 2021

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions