Ability to disable TS8010: 'types' can only be used in a .ts file.

Search Terms

TS8010
TS 8010
types can only be used in a .ts file
'types' can only be used in a .ts file

Suggestion

Ability to disable TS8010: 'types' can only be used in a .ts file. Type annotations could simply be ignore by tsc when compiling a .js file.

Use Cases

I work in a JS / TS blended codebase. My team uses WebStorm as our IDE, and it supports type annotations in .js files. When a variable/param is typed, it provides type-specific autocompletion. As you can imagine, that's quite powerful when working in a JS environment. Consequently, we have thousands of type annotations throughout our JS files. We would like to add allowJs:true to our tsconfig.json, however tsc throws an error for every type annotation in each JS file.

Checklist

My suggestion meets these guidelines:

• [ x ] This wouldn't be a breaking change in existing TypeScript/JavaScript code
• [ x ] This wouldn't change the runtime behavior of existing JavaScript code
• [ x ] This could be implemented without emitting different JS based on the types of the expressions
• [ x ] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• [ x ] This feature would agree with the rest of TypeScript's Design Goals.

Start with the TS8010 diagnostic and the allowJs option in tsconfig.json, then trace how tsc reports type annotations in .js files. Done means a configuration can disable this diagnostic without changing emitted JavaScript behavior.