Compile libraries with --strict=false, but compile src with --strict

[ORESoftware]

Search Terms

strict mode, strict, skipLibCheck

Suggestion

Allow uses to use:

skipLibCheck: false,
libCheckMode: 'non-strict' 

what it means is users want to re-compile library code (for some reason?), but want to switch strict mode off for library code.

Use Cases

I maintain a few libraries written in TS and sometimes users will say my library doesn't compile in strict mode. I prefer to not use strict mode. So I can tell my users to use compilerOptions.skipLibCheck = true, but sometimes they don't want to skipLibCheck, so it would be nice for them to skip strict checking for libraries, but do strict checking for their own code?

important: I may have a misunderstanding - it could be that tsconfig.json in node_modules projects override the end-user's settings, so perhaps I can prevent strict mode for library, in the case that my library only compiles in non-strict mode?

Checklist

My suggestion meets these guidelines:

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

[sandersn]

No, you are right, all files in a compilation have to use the same settings. There is no way for a library to compile in non-strict, but have source compile in strict.

[ORESoftware]

Ok thanks.

Then this would be a feature request - it would be nice to compile libraries in strict and source in non-strict, or vice versa. Even compiling certain libraries as strict and certain ones as non-strict, perhaps according to their tsconfig.json files (if those are not excluded by .npmignore etc).

[sandersn]

I thought we had seen this request before but I can't find it. This is a surprisingly complex feature, so we need some kind of proposal that thinks through the issues.

[MartinJohns]

@sandersn You were probably thinking of #31035.

[sandersn]

Yep, that's it. Thanks @MartinJohns