Haskell Code Spot

Visual tool to spot odd runtime behaviour of Haskell programs.
Keywords: data scientist, GHC eventlog, UI experiments, creative/live coding

NOTE: GHC-WPC is optional, Haskell Code Spot works with vanilla GHC eventlog out of the box.

Blog

• WebUI for Haskell tooling!

Learn these for coding

• HTML + CSS + JS (https://www.youtube.com/kepowob/featured)
• Svelte (https://svelte.dev/tutorial/basics)
• D3.js (https://www.youtube.com/watch?v=_8V5o2UHG0E)
• D3 flame graph (https://github.com/spiermar/d3-flame-graph)
• C3.js (https://c3js.org/)
• CodeMirror (https://codemirror.net/doc/manual.html#api)
• Scotty (https://hackage.haskell.org/package/scotty)
• GHC RTS design (https://takenobu-hs.github.io/downloads/haskell_ghc_illustrated.pdf)
• GHC Eventlog (https://www.well-typed.com/blog/2019/09/eventful-ghc/)
• ghc-events library (https://hackage.haskell.org/package/ghc-events)
• GHC HIE files (https://www.haskell.org/ghc/blog/20190626-HIEFiles.html)

Quick Start Guide

In one terminal:

$ (cd server && stack build && stack exec code-spot-server)

In another terminal:

$ (cd client/src && npm install && npm run dev)

Now open http://localhost:5000/ in your browser!

You will see a visualisation of data/grin.eventlog (change in client/src/App.svelte).

How to build your eventlog

If stack project is used, profiling must be enabled. After compiled with profiling, one need to run it with RTS options plh.

stack build --profile --executable-profiling --library-profiling
stack exec --profile EXECUTABLE -- ARGUMENTS +RTS -p -l -h

Previews:

This project is still in the proof-of-concept phase, but we had a great fun implementing the initial version of heap inspections and the step-by-step debugger. All of these features are based on visualizing the EventLog from GHC.

Heap Live

Heap Size

Cost Center based stack trace in step-by-step style. See the demo video.