• Platform.worker

What can you do with Elm?* Html * Http * Ports * Web Components

Different techniques for extending elm* elm-pages StaticHttp API * Elm radio episode 1 on elm pages * elm-graphql * Codegen * Macros * Elixir exunit * Wrapper elm apps * Can emulate effect managers * Platform.worker * Introspection * elm-typescript-interop * Ports and flags * Web Components * Code transformation * Elm asset loader webpack * Hacking JS to get FFI * Depending on internal details could end up with broken code

elm-hot and elm-hot-webpack-loader

Pitfalls and considerationsCodegen

• Have a single clear source of truth for codegen
• Prevent bad states with airtight abstractions, rather than having lots of caveats
• Make sure public APIs for generated code look nice
• Use doc comments

Macros

• Elm code that doesn’t look like elm code
• Tooling doesn’t work then - see Babel ecosystem
• Violates Open close principle - you’re modifying the language, not extending it

Provide a platform with extensions in mind when you build tools so you don’t require users to hack

When you build a tool, think about the mental model for uses, let that guide you. Avoid leaky abstractions

Be opinionated about the core things, and unopionated about what’s not essential to the tool

• [elm-spa](https://github.com/ryannhg/elm-spa)