Common Bundles

Quirk: the minChunks option and the meaning of infinity

What the official webpack documentation has to say on this:

The minimum number of chunks which need to contain a module before it’s moved into the commons chunk. The number must be greater than or equal 2 and lower than or equal to the number of chunks. Passing Infinity just creates the commons chunk, but moves no modules into it. By providing a function you can add custom logic. (Defaults to the number of chunks)

The possible values this option can have are:

• number
• Infinity
• function(module, count) -> boolean

Not setting the value to Infinity implies that if a module seems to be referenced by more than one bundle, it will also be added to that bundle (even if it was not listed in the module list for the entry the plugin was defined for.)

How this affected us was in the following situation: at some point, a mini-app appeared in our code-base that had a dependency on a module (say, lodash) of a different version than the one in the base app. The base app's dependency was being served in the common bundle, and we found out as time went by that the dependency of the mini-app was also being served in the bundle.

However, that mini-app was never meant to use the common bundle; its own dependencies were meant to be bundled along with its application code. At run- time, you'd find out that the mini-app couldn't run because some of its dependencies were no longer found by webpack - that is, they are residing in the common bundle (vendor.js) which was never sourced by the HTML.

This is where the minChunks: Infinity option came into play: it instructs webpack to not add any module into the common bundle except for those listed in the entry the plugin is defined for. That's what we were after; the base app has its dependencies rolled up in the common bundle (vendor.js) and the mini-app's dependencies are bundled inline along with the rest of its code.

In mortal-webpack, this is the default behaviour (through the strict option accepted by builders.generateCommonBundle.) It is still possible to override it by passing pluginOptions to that API and configure the plugin directly, but be warned!