In the current Angular CLI (Angular 8 at the time of this writing) the tooling for libraries is really good except for one area, assets. Unlike when you build a project for production, building a library does not package assets like you might expect.
tl;dr – the boiled down steps
- Build the library
- This article uses the vanilla AngularCLI
- Copy the assets to the dist folder of the built project
- I use npm scripts with pre/post prefixes
- Optional – publish as npm package
- Update the project to import the assets
Building the Library with Assets
Under the covers of the Angular CLI, library projects uses ng-packagr to bundle up the code for the library for distribution. ng-packagr is almost the same as the packaging that the CLI uses for app projects but it has some crucial differences in how it does it’s packaging, such as it doesn’t bundle in assets such as fonts, images, and scss files.
There are cases where you need this functionality though and if the Angular CLI doesn’t give it to you, what do you do? Right now, you need to post-process the package so that you include the assets.
In a past project I have used CPX for file copy/globbing but it doesn’t work on all systems. (I work on a Pixelbook and I failed to get it working properly.) I know there are many other npm modules that allow for file copying, this was the one that seemed the most stable, however it also doesn’t seem to be maintained currently. Basically, I’d use it again if I needed it but I would look for other options first. ( CPX – https://github.com/mysticatea/cpx )
This isn’t about what tools to use, so for this example I’ve used a simple shell script to illustrate what you need to do in order to package up assets.
No matter what you use to copy the files over, you need to have it as part of your build process. I prefer a stripped down build system that is easily understandable. To do this, I use npm scripts and the ability to use pre and post prefixes on steps to make them easily understood.
// Sample build script
"build-lib": "ng build lib-with-assets",
Including Styles from a Library
To include style paths more cleanly for scss imports, you can take advantage of the stylePreprocessorOptions setting in the Angular CLI. If you are using scss for your styling, this will allow you to do @import statements with just the file name and not the entire path to the dist directory or the node_modules directory if you published as an npm repo.
If you have published as an npm module, then I don’t believe you will need to do this step and instead can use the ~ at the front of the package name to import, since the CLI knows that SCSS @imports with a tilde come from node_modules.
This is the basics of getting set up and by no means covers every situation. If you have additional information or questions, I would love to get your feedback.
I created a sample repository as a test bed for exporting assets as part of the library project. You can find it over on GitHub. https://github.com/vandermore/angular-library-with-assets
References: (Since we stand on the shoulders of giants to see further.)