Make react-router-dom treeshakable

[TrySound]

Ref #6464

Here's the problem. Babel transpiles static class properties outside of class iife which blocks uglify/terser from this iife.

defaultProps will become a bad pattern soon since it's blocks treeshakability. For functions the problem is even more aggressive since it's not solvable these days.

I think the best we may do is use defaults in destructuring

const Component = ({ prop1 = 'a', prop2 = 'b' }) => {
}

With classes this is harder because defaults can't be propagated in all methods.

[billyjanitsch]

Thanks for looking into this @TrySound! Can you explain why this solution is preferred over simply not bundling the package into a single file for the ESM build? In other words, what is the advantage of bundling the file?

[TrySound]

With single bundle it is easier to control size and output. It's bundled faster. More consistency in imports. Less import statements. Internals in splitted files are hidden which is the most important.

Treeshaking is machine work. Splitting imports with paths is user work.

[mjackson]

Thanks, @TrySound! I'll take a look at eliminating defaultProps from the react-router package.