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--watch flag makes neuron crash due to non-exaustive matching by Reactor.hs #679

Description

@jcborras

Little to add to what the subject says. Site generation is fine but the file system watch feature makes neuron crash.

Steps to reproduce the behavior:

  1. neuron -d . gen works fine:
   Plugins enabled: dirtree, links, tags, neuronignore
   Loading directory tree (2705 .md files) ...
   Building graph (2706 notes) ...
   Building route data ...
   Rendering routes (2707 slugs) ...
🥅 Nothing updated in output directory
  1. neuron -d . gen --watch produces:
   Plugins enabled: dirtree, links, tags, neuronignore
   Loading directory tree (2705 .md files) ...
   Building graph (2706 notes) ...
   Building route data ...
   Rendering routes (2707 slugs) ...
🥅 Nothing updated in output directory
neuron: src/Neuron/Reactor.hs:(219,35)-(227,44): Non-exhaustive patterns in \case

HasCallStack backtrace:
  bracket, called at lib/System/IO/Utf8.hs:154:24 in with-utf8-1.1.0.0-ErmN3rUvJv42z4OzMNWvfT:System.IO.Utf8

Questioning the LLMs on this matter they suggest me to keep the folder with my .md zettel files clean of everything else than files with that extension.. but I have folders for particular topics and static content (ie. png files) in my zettelkasten. Maybe you find that bit of information useful.

Environment:

  • Ubuntu Linux 26.04.01 LTS
  • Neuron version 1.9.37.0

I acknowledge that this project is in maintenance mode.

Activity

  1. srid commented on Sep 28, 2026

    @srid
    Owner

    Thanks for the report! This was caused by a newer fsnotify version adding file-event types that neuron didn't handle, so it crashed on the first file save. It had nothing to do with non-.md files or subfolders in your zettelkasten.

    A fix is in #680. Could you check whether it fixes it for you? You can try it with:

    nix run github:srid/neuron/fix-watch-crash-679 -- -d . gen --watch
    
  2. jcborras commented on Sep 28, 2026

    @jcborras
    Author

    I hereby confirm that the said branch fixes the issue.

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