rollup Command: Bundle Libraries in CI

rollup bundles ES modules into clean, tree-shaken output for libraries.

rollup is a module bundler favored for libraries because of its small, tree-shaken output and first-class ES module support. In CI it builds distributable bundles in multiple formats (ESM, CJS, UMD) from a config file.

Common flags

-c / --config FILE - use a rollup config file
-i / --input FILE - set the entry module
-o / --file FILE - single output file (-d/--dir for code splitting)
-f / --format esm|cjs|umd|iife - output module format
-m / --sourcemap - emit a source map
-w / --watch - rebuild on changes (local, not CI)
--environment KEY:VALUE - pass env vars to the config

Example in CI

Build an ESM bundle with a source map from the project config:

shell

rollup -c rollup.config.mjs --environment NODE_ENV:production

Common errors in CI

Unexpected token (Note that you need plugins to import files that are not JavaScript)
(!) Unresolved dependencies - add @rollup/plugin-node-resolve
Circular dependency: a -> b -> a
"X" is not exported by "Y" - named import does not exist (often a CJS module)

Key takeaways

rollup excels at library bundles with multiple output formats via -f.
Most "Unexpected token"/"Unresolved" errors mean a missing rollup plugin.
Use -d/--dir instead of -o when emitting multiple chunks.