Erriscope

What is it?

This is a lightweight GHC plugin that provides an ergonomic web UI for viewing the errors and warnings emitted during compilation. It seeks to improve the developer experience for a REPL based workflow.

Advantages over viewing errors in the terminal include:

• A summary view of all errors organized by module and showing only the first 4 lines of each error message.
• A view containing the complete error message with added syntax highlighting.
• Warnings persist across reloads which is an issue with GHCi.

Quickstart

• Install the server component:

  > cabal update && cabal install erriscope-server

  or

  > stack update && stack install erriscope-server

• Start the server:

  > erriscope-server

• Start up a REPL with the following arguments to enable the plugin:

  > cabal repl -b erriscope --repl-options="-fplugin Erriscope"

  or

  > stack repl --package erriscope --ghci-options "-fplugin Erriscope"

• Point your browser to localhost:8888

User's Guide

You can use the Shift+UpArrow and Shift+DownArrow hotkeys to quickly cycle through errors.

You can change the port on which the server and plugin run using command line arguments. For example, if you want to run the server on port 8000, start the server as follows:

> erriscope-server 8000

and add the additon GHC plugin option:

> cabal repl -b erriscope --repl-options="-fplugin Erriscope -fplugin-opts Erriscope:8000"

Issues

• Erriscope currently only supports GHC 9.6.*.