preserveModules creates wrong output

[johannes-z]

• Rollup Version: ^2.26.4
• Operating System (or Browser): Ubuntu 1804
• Node Version (if applicable): 10.19.0
• Link to reproduction (IMPORTANT, read below): https://repl.it/repls/KindlyHospitableDataset

Expected Behavior

The emitted lib folder should look like this:

• main.js
• HelloWorld.vue_rollup-plugin....js
• HelloWorld.vue.js

Actual Behavior

The emitted lib folder looks like this:

• node_modules/
• src
  • HelloWorld.vue_rollup-plugin....js
  • HelloWorld.vue.js
• main.js

The plugins resolve and commonjs do nothing to remedy this, also adding those libraries added to node_modules to externals does nothing.

Additional

In a monorepo, all the files within lib are also under the path the monorepo is under, i.e. if the package is in /my-project/packages/my-package, the output will look like this. /my-project/packages/my-package/lib/package/my-package/main.js

[lukastaegert]

The answer is simple: There are several files from node_modules that are included in the build, and preserveModules preserves the directory structure. If you do not want this, or you want some partial bundling, I fear your only option would be to put all files that you want as separate inputs as an array into the input property.

[johannes-z]

Shouldn't marking those node_modules as externals be sufficient to not have them copied to the dist folder? I tried a number of ways preventing those node_modules from ending up in my dist folder, but nothing seemed to work. Especially @rollup/plugin-commonjs always messed up the dist folder because it creates a _virtual folder.

[lukastaegert]

Hmm, I thought ids were passed twice through external, but apparently only unresolved ids are passed here. Will need to check this again. Anyway, if you use a function for external you can log what ids are passed here and add those to external that are needed. In your case

external: ['tslib', 'vue', 'vue-class-component', 'vue-property-decorator', 'vue-runtime-helpers/dist/normalize-component.mjs']

did the trick. Or if you do it via a function

external(id) {
  return id === 'tslib' || id.startsWith('vue');
}

and last via regular expression

external: /^(tslib$|vue)/

[lukastaegert]

Fix for the external behaviour here: #3753. This was apparently overlooked for quite some time.

[johannes-z]

Thanks! Seems to work for me now.

[cimchd]

Just in case someone (like me) finds this topic first. In a monorepo it may help to also add preserveModuleRoot option.

See: rollup/plugins#321