Using Harper Language Server with Helix Editor

First Install Harper using the method appropriate for your OS.

Then add the following to languages.toml

[language-server.harper-ls]
command = "harper-ls"
args = ["--stdio"]

Restart Helix Editor.

Now you should see squiggly lines under incorrectly spelled words. 🎉

In order to see (and possibly choose) the correct spelling, take the cursor on the error and space a (Code actions)