F# Fable 2.0 -> 2.1

This morning one of my colleagues ran into a weird error when trying to build one of our web applications with Fable:

ERROR in ./src/path/to/your/Client.fsproj Module build failed (from ./node_modules/fable-loader/index.js): Error: Cannot find module ‘fable-compiler’

At first I was very confused because as far as I could tell, fable-loader didn’t use a module called fable-compiler.

But then I remembered something from Twitter: there were plans to eliminate the dotnet cli tool in the next Fable release and replace is with a javascript module again. Yeey for reading Twitter!?

Steps to update to Fable 2.1 (from Fable 2.0):

Update yarn

Add fable-compiler and npx and upgrade fable-loader to the latest version.

> yarn add fable-compiler --dev
> yarn add npx --dev
> yarn upgrade fable-loader@latest


Old New
“fable-loader”: “^2.0.0” “fable-loader”: “^2.1.2”
- “fable-compiler”: “^2.1.8”
- “npx”: “^10.2.0”

Update paket

Remove clitool dotnet-fable from your paket.dependencies and paket.references

Update build scripts

Instead of using the cli tool, you need to update your FAKE5 script to work with npx or yarn

Yarn.exec "npx webpack --config whatever/the/path/is/to/webpack.config.js"  (fun o -> { o with WorkingDirectory = "whatever/the/path/is/to/client.fsproj" })