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Our minimal wrapper for using elm-pages scripts to write all our non-compiler Lamdera tooling in Elm.

This is a work-in-progress and could do with some cleanup, but is functional.

You may find it useful if you like our top-level design choices.

Differences to elm-pages scripts

Our CLI tooling is aligned to specific design choices:

  • The only STDOUT output should be output controlled and intentionally specified by the Elm code
  • Every effect that reaches out into the world (including reads) should always be logged to disk
  • The output of that logging to STDOUT should be optional (LDEBUG=1 ENV flag)

As a result:

  • Wrapped elm-pages scripts output to remove the default BackendTask.Custom.run and HTTP fetch debug output
  • Most effects are implemented (or re-implemented) in custom-backend-task.ts including error handling with clear input context
  • Logging is written to controlled files, i.e. run-2024-03-22021333196Z.log
    • This means you're never left wondering "wait hold on, what happened exactly?" when things go wrong or unexpectedly – you can always check the logs for a full audit of everything the script did
    • Running with DEBUG=1 will print those same logs to the console as well when you do want to see the output
  • 🔥 Extensive use of emojis in logging to identify effects, after a while it becomes amazingly easy to skim & understand what's happening vs raw text logging

Other opinionated things:

  • type alias IO a = BackendTask FatalError a, everything in src/IO/* uses this alias
  • Not everything in elm-pages has been wrapped, i.e. the bashStream was setup before BackendTask.Stream was a thing.
  • Anything from elm-pages core BackendTask.* is usable, but will be missing the logging and error handling implemented in custom-backend-task.ts, which would defeat the point of this approach.

Otherwise lamdera/script is just entirely using elm-pages scripts.

Usage

./run.sh <command> [args].

$ ./run.sh example --someArg testing
───> Starting a thing for testing...
It's a mac!

$ cat run-2024-08-11073005957Z.log
runLogPath: /Users/mario/dev/projects/lamdera-script/run-2024-08-11073005957Z.log
runId: 2024-08-11073005957Z
DEBUG:1
isDebug: true
───> Starting a thing for testing...
debug: debug:👀💻:MacOS
It's a mac!

See src/Lx.elm for the example CLI implementation, this is where you would implement your own CLI like normal.