Enough rebases, should be good to go now.

The script runs fine on Mac, I use it as part of npm run test-all. I expect the underlying problem is it is relying on wildcard expansion by shell.

% npm run typescript-checkJS

> commander@11.0.0 typescript-checkJS
> tsc --allowJS --checkJS index.js lib/*.js --noEmit

% echo $?
0

The script runs fine on Mac, I use it as part of npm run test-all. I expect the underlying problem is it is relying on wildcard expansion by shell.

% npm run typescript-checkJS

> commander@11.0.0 typescript-checkJS
> tsc --allowJS --checkJS index.js lib/*.js --noEmit

% echo $?
0

Checked it on Debian and the result was the same as what you get.

However, it isn't correct. There are currently a lot of type errors in the code and we are supposed to see them, instead we see nothing.

Even when running the command for one individual file that has type errors (a lot of them) and with the exact option names from TypeScript's documentation, it still doesn't output anything:

$ npx tsc --allowJs --checkJs lib/command.js --noEmit
$ echo $?
0

So the command has been misleading the entire time even if it has been in use, so renaming it might not be a good idea.

Good read: Why you should always quote your globs in NPM scripts

There are (at least!) 3 different things going on:

• // @ts-check only works as the first line of the file
• lib/*.js in run-script typescript-checkJS does not work on Windows
• run-script typescript-checkJS generates far less errors than when enable checking in VSCode editor

The command-line help gives one clue, specifying the files apparently uses the default compiler options:

tsc app.ts util.ts
  Ignoring tsconfig.json, compiles the specified files with default compiler options.

I haven't yet managed to get VSCode to do the gentler type checking that typescript-checkJS implicitly uses, but it may just be difference between tsconfig.json and default compiler settings.

Managed to get looser checks matching run-script in VSCode with both of these in tsconfig, so at least reproducible behaviour now:

   "checkJs": true,
   "strict": false, 

Closing in favor of #1969.