Tree shaking of vue library

[dandel10n]

Bug report

What is the current behavior?
I have a Vue icons library (npm package), which is using rollup to build the code in various formats (including ES modules) which should be tree-shakable. When I add it to my project, which is built with webpack, and use only one icon from the library, I still see whole library in the production bundle.

If the current behavior is a bug, please provide the steps to reproduce.

I've made super simple vue cli app https://github.com/dandel10n/vue-app-sample - which uses https://github.com/dandel10n/vue-library-sample for easier illustration.

There are 3 components in the library. In the app I use only one (LibComponentOne). But in the vendors.bundle.js I still see all three components being imported.

If I build the app in dev mode with passing optimization: { usedExports: true } then in the bundled js file I see the unused components marked as /* unused harmony export LibComponentThree */\n/* unused harmony export LibComponentTwo */ as expected. But in production build I still see the unused components being included.

What is the expected behavior?

As I understand in app's vendors bundle I should see only one component, not all 3.

Other relevant information:
webpack version: v4.28.4
Node.js version: v10.15.0
Operating System: macOS
Additional tools: Vue CLI, Rollup

[sokra]

https://github.com/dandel10n/vue-library-sample/blob/master/src/entry.js

Here you "use" all components no matter which one are referenced by the user.

Even if this would be fixed, the way rollup-plugin-vue generates component code doesn't allow tree-shaking as it would be considered as side-effect.

I think this would help:

- var LibComponentOne = normalizeComponent_1(
+ var LibComponentOne = /*#__PURE__*/normalizeComponent_1(
    { render: __vue_render__, staticRenderFns: __vue_staticRenderFns__ },
    __vue_inject_styles__,
    __vue_script__,
    __vue_scope_id__,
    __vue_is_functional_template__,
    __vue_module_identifier__,
    undefined,
    undefined
  );

Send a PR to rollup-plugin-vue to fix that.

And fix your entry.js. Remove the global Vue registration in the esm.js build.