fix(commonjs): __moduleExports in multi entry + inter dependencies

[danielgindi]

Rollup Plugin Name: commonjs

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers: #411

Description

When a module is a main entry point but still imported by another module (due to multiple entries feature), we can now detect that and properly export __moduleExports.

Tests

I've had to modify the form tester to support multi-entry situations. (In the function tester it does not make a lot of sense as we run the code in memory where it would expect to have other generated outputs to exist on disk for importing).

[shellscape]

@danielgindi please have a peek at that snapshot when you have the chance and then we'll merge

[lukastaegert]

I'm also gonna have a small peek in a second

[lukastaegert]

Two comments, and I am also missing the updated snapshots in the markdown file, did you commit this?

[lukastaegert]

So you said we cannot get rid of __moduleExports because it will trigger interop handlers when using the default export? The thing is, this will now taint entry points in a way that users will notice there is suddenly a new named export that does not belong here. So one could wonder if for entry points, we might rather use the default even though it triggers interop? But I am undecided, what do you think?

[danielgindi]

Well this only happens for entry points that are being imported by other code paths in the bundle.
So in most use cases - it will not be exported.
And in the use cases where it does - it's due to its use by one of the other entry points.

Unfortunately I don't see any way around it without breaking code... But if I think of some other trick to get rid of this, I'll make a PR :-)

[danielgindi]

I'm having issues with prettier modifying form test outputs, where the transformer creates a var and prettier converts to a const. This forces me to bypass commit hooks.
I'm thinking we need to change the var outputted from the transformer to const, and configure prettier to avoid form outputs.

[lukastaegert]

I'm not sure about the var, would be a first we are creating ES2015+ output, except for the imports and exports of course. Seems like a waste to just use a const but not go all-in with the other features like arrow functions. For now, I would rather keep it a var.

But yes, test output should not be covered by prettier. Did you try extending the .prettierignore file? Not sure in how far it supports globs, I hope so. Otherwise one could try to tweak the lint-staged config in the central package.json file, but that seems harder to me.

[FredKSchott]

This is great, thank you @danielgindi!