Allow preservation of dynamic import with variable in CJS

[nzakas]

Feature Use Case

Because Node.js supports both require() and import() in CommonJS files, it would be helpful to be able to retain import() calls instead of translating them into require(). Here's a very simple example of what I'm trying to do:

https://rollupjs.org/repl/?version=2.71.1&shareable=JTdCJTIybW9kdWxlcyUyMiUzQSU1QiU3QiUyMm5hbWUlMjIlM0ElMjJtYWluLmpzJTIyJTJDJTIyY29kZSUyMiUzQSUyMmV4cG9ydCUyMGZ1bmN0aW9uJTIwZG9JbXBvcnQoc3BlY2lmaWVyKSUyMCU3QiU1Q24lNUN0cmV0dXJuJTIwaW1wb3J0KHNwZWNpZmllciklM0IlNUNuJTdEJTIyJTJDJTIyaXNFbnRyeSUyMiUzQXRydWUlN0QlNUQlMkMlMjJvcHRpb25zJTIyJTNBJTdCJTIyZm9ybWF0JTIyJTNBJTIyY2pzJTIyJTJDJTIybmFtZSUyMiUzQSUyMm15QnVuZGxlJTIyJTJDJTIyYW1kJTIyJTNBJTdCJTIyaWQlMjIlM0ElMjIlMjIlN0QlMkMlMjJnbG9iYWxzJTIyJTNBJTdCJTdEJTdEJTJDJTIyZXhhbXBsZSUyMiUzQW51bGwlN0Q=

Feature Proposal

Add a preserveDynamicImports option that can be set to:

• "all" - never rewrite import() regardless of the value passed in
• "variable" - only preserve import() if it's used with a variable, otherwise overwrite as usual
• "static" - only preserve import() when passed a constant

[lukastaegert]

Fix at #4647, though with only a boolean switch (and on by default). For more fine-grained control, you can still use the plugin interface.

[nzakas]

Nice, thank you!

[rollup-bot]

This issue has been resolved via #4647 as part of rollup@3.0.0-8. Note that this is a pre-release, so to test it, you need to install Rollup via npm install rollup@3.0.0-8 or npm install rollup@beta. It will likely become part of a regular release later.

[rollup-bot]

This issue has been resolved via #4647 as part of rollup@3.0.0. You can test it via npm install rollup.