jfmengels / elm-prefab

Maintainable code generation for Elm Apps

Elm Prefab

Prefab (Noun)
A prefabricated building or structure that is manufactured in sections, typically in a factory, and then transported and assembled on site to form a complete structure.

Prefab (Adjective) A portmanteau of "Pretty" and "Fabulous" ✨

Elm Prefab is a collection of codegeneration plugins for generating and maintaining an Elm app.

Each plugin is independent, so you can pick and choose what you want.

• App - A base app architecture that has

  • Page-level state caching
  • Notion-like flexibility for viewing multiple pages at once.
  • Routing generation - Spend as little time futzing with routes as possible!
  • Built-in support for elm-program-test for full end-to-end testing of your Elm app.

• Assets - Be able to link to a static asset

• GraphQL - Write GraphQL queries and mutations and get Elm code to use them! (Powered by vendrinc/elm-gql)

The Elm Architecture is a very stable way to build apps, but there are some nuances to master.

This project is born out of years of experience working on large(>500k lines) Elm apps at Blissfully and now Vendr.

This is for those who want to speed up development for new projects and avoid some tricky situations that become expensive to fix later on.

Getting started

In general, elm-prefab has a config file called elm.generate.json, and you run elm-prefab to generate the code.

Getting started

# navigate to your projects directory and install `elm-prefab`
npm install --savedev elm-prefab

# Running `elm-prefab` will generate working
npm run elm-prefab

Note for PNPM - If you're using pnpm, you may run into an error that says elm-dev not found In this case you may need to run pnpm install --save-dev elm-dev, elm-gql

When running elm-prefab for the first time, a number of files will be generated.

You can take a look in the examples folder to see what is generated on the first run.

• .elm-prefab - Files in the .elm-prefab directory are owned by elm-prefab. Take a look, but know that they will be overwritten as needed.
• src/* - Elm files will be generated in the src directory and are owned by you, meaning you can modify them as you want! Once they're generated, elm-prefab doesn't modify them.
• src-js/* - These are some JS, HTML, and CSS files that are also owned by you!
• There are also a number of config files that will be generated at the root of your project, including
  • elm.json
  • package.json
  • tsconfig.json
  • vite.config.js

Note - Vite, Typescript, and NPM are not required to use elm-prefab, it's just convenient to include them.

Starting the Vite development server

Once you've run npm run elm-prefab, you now have a working Vite setup.

npm run dev will start a dev server so you can get coding!

Running npm run build will build things for production, with the resultant files in the dist folder. Feel free to check out the ViteJS docs

The first place to look

elm-prefab has generated src/Page/Home.elm for you, let's take a look.

If you've worked with elm before it should be pretty familiar as a standard model/update/Msg/view thing.

The next place to look is src/Main.elm.

This is the global part of the app. This is where you can control:

• Global layout, including showing multiple pages in one layout.
• Authentication logic.
• Any other "App-wide" thing you might want.

Now go build something! If you have a questions, check out the below guides.

• Adding a new page

• Using local storage

• Managing routes and pages

• Managing assets

• Using GraphQL

FAQ

• Why does this thing exist?
• Why is routing handled like it is?