Not removing / tree shaking unused imports with sideEffects: false when define is used

[natew]

Here's a small repro:

https://esbuild.github.io/try/#dAAwLjE5LjUALS1kZWZpbmU6cHJvY2Vzcy5lbnYuVEVTVD0nIjAiJyAtLW1pbmlmeQBpbXBvcnQgeyBqb2luIH0gZnJvbSAncGF0aCcKCmlmIChwcm9jZXNzLmVudi5URVNUID09PSAnMScpIHsKICBqb2luKCcnLCAnJykKfQ

Edit: So it works with bundle mode, is this meant to only work in bundle mode?

Though not perfect in the sandbox because you'd want a separate module with sideEffects: false to show it.

Basically esbuild will leave behind imports, which then doesn't play along nicely with esbuild later on in your build which will complain:

▲ [WARNING] Ignoring this import because "../../packages/xyz/dist/index.js" was marked as having no side effects [ignored-bare-import

The combination of the two behaviors makes for unavoidable warnings, ideally esbuild should be able to remove imports like the above.

[evanw]

The transform API and the build API with bundling disabled just pass through all imports unmodified. You need to enable bundling for esbuild to traverse into import paths.

[natew]

I think either adding a way to tell esbuild to ignore the warnings, or to allow shaking of imports in build mode would be very useful.

I can't bundle things in this case because it's a library that needs to let consumers of it tree-shake it. But without removing the side-effect-free imports, esbuild then outputs tons of warnings to end users as they run their bundler.

How hard would bringing the import analysis / removal portion from bundling into build be?

[evanw]

tell esbuild to ignore the warnings

This is the way: https://esbuild.github.io/api/#log-override. Pass the log message name (in [...] at the end of the warning) to log override to adjust the log level.