I'm currently working on creating a function, test.isolated(), which wraps around jest.isolateModules. This function takes an array of strings representing the modules to be imported, along with the usual arguments (name, fn, timeout), and then injects an object containing each imported module by name as the first parameter of fn.
The implementation of test.isolated() using proxies is straightforward. However, I am trying to figure out how to strongly type the first argument.
I have noticed that VS Code's TypeScript engine can determine the type of exports from an imported module. Is it feasible to infer this type (the return type of require()) based on the module path?
In my initial attempt:
type ModuleType<M extends string> =
((m: M) => ReturnType<NodeRequire>) extends ((m: M) => infer U) ? U : never;
type T = ModuleType<'fs'>;
Interestingly, regardless of what value I provide for M, T always resolves to typeof Electron. It seems like in my project, ReturnType<NodeRequire> itself is typeof Electron.
In my second attempt:
type ModuleType<M extends string> =
((m: M) => NodeRequire['main']['exports']) extends ((m: M) => infer U) ? U : never;
type T = ModuleType<'fs'>; // => any
Any thoughts or suggestions? Or is this type inference task impossible?
Edit:
Upon further investigation, I have found that the return type of require() is always any. Only the import syntax can infer a type.