How do I discover Elm's REPL in VS Code? - visual-studio-code

Question

How do I discover Elm's REPL in VS Code?
Specifically, I have no clue how to get up and running with Elm and VS Code.
My past experience involves using F# and Visual Studio.
How do I send instructions to Elm's REPL?
Where is Elm's REPL located within VS Code's IDE?
Any suggestions?

Answer 1

Once you've installed the Elm package, you can use the Elm: REPL - Start command to start a REPL session.
(You access this command the same way as you access other commands in VS Code: by opening the Command Palette. This can be done through the View menu (View -> Command Palette) or with a keyboard shortcut (Ctrl + Shift + P or Cmd + Shift + P, depending on whether you use Windows or Mac).
Once the session has started, you can send lines or selections to the REPL. Type a line into your editor, then run the Elm: REPL - Send Line command to send it to the REPL. There is a default keyboard shortcut for this (Alt + /) as well.
If you want to send more than a line, highlight the thing you'd like to send (probably a function or value definition), and run the Elm: REPL - Send Selection command. Again, there's a keyboard shortcut: Alt + Enter.
Note that the REPL does not support type annotations; sending type annotations to the REPL will result in an error. You can still annotate your function and value definitions in your code, but when you highlight the definitions to send to the REPL, just make sure not to highlight the type annotations.

Answer 2

If you're just looking to play around in the Elm repl, just do this:
1) install Elm globally (using npm, or using an installer from elm-lang.org)
2) open VS Code, then press CTRL + ` (or Cmd + ` on a Mac); this opens VS Code's built-in terminal
3) type elm-repl -- this starts elm's repl, and you can try out snippets, etc
However since your real question is about getting up and running w/ Elm in VS Code, here's a start:
1) download/install elm-format from https://github.com/avh4/elm-format
2) install VS Code
3) install VS Code extension "elm" (it's by a Sascha Brink); add "elm.formatOnSave": true to your VS Code settings
Now when you create/edit a .elm file you'll get code coloring, etc.
If your Elm code is for an app (as opposed to repl snippets), you'll want to see results in elm-reactor. So start a VS Code terminal (see above), type elm-reactor, and your app should be served at http://localhost:8000

Answer 3

In short; You don't want to use vscode (yet) for Elm development. Either go with Atom (Elmjutsu) or IntelliJ (CE works fine with the elm-plugin).
You get support for refactoring and fast navigation. The reason I don't recommend using vscode is because the elm-plugin is underdeveloped.
Unfortunately, the elm-plugin with IntelliJ also is a little underdeveloped, since it does not underline-highlight errors in your sourcecode – so tracking errors does have a cognitive tax.
I know that this question is related to the elm-repl and the possibility to send your selection to the repl is a nice one. But it only saves you two shortcuts (copy selection, send to repl vs copy selection, alt-tab to repl, paste and enter). The way lines are formatted (in elm-format) renders send-single-line as mostly a not-properly-thougth-through feature.
What I do is open a terminal and open elm-repl there, and I split my screen so I always have the output available.