Gleam language server rebuilds trigger constant page reloads

[alixinne]

Hello! New to Gleam & Lustre so I hope it's not something wrong with my setup, but I have noticed the following issue while following the Lustre tutorial.

When running a project based on the Full stack applications with the following commands:

# In client/
gleam run -m lustre/dev start

# In server/
gleam run

Editing a file in Neovim with the Gleam LS running results in the browser hot-reloading the page on every keystroke. Here's the browser console log after typing 3 characters in the src/client.gleam file:

Opening http://localhost:1312/
[lustre] Connection lost, attempting to reconnect... server-hot-reload.js:92:13
[user-agent leaked] using async method http://localhost:1312/ isolated.js:102:15
[lustre] Connected to development server server-hot-reload.js:42:13

[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css 2 server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17

Disabling the language server stops the issue occurring on every keystroke, but it still seems that writing the file triggers multiple reloads, followed by a full page reload:

Opening http://localhost:1312/
[lustre] Connection lost, attempting to reconnect... server-hot-reload.js:92:13
[user-agent leaked] using async method http://localhost:1312/ isolated.js:102:15
[lustre] Connected to development server server-hot-reload.js:42:13

[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css 2 server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
[lustre] Asset updated client.css server-hot-reload.js:66:17
Opening http://localhost:1312/
[lustre] Connection lost, attempting to reconnect... server-hot-reload.js:92:13
[user-agent leaked] using async method http://localhost:1312/ isolated.js:102:15
[lustre] Page reloaded by hot reload server-hot-reload.js:11:13
[lustre] Connected to development server server-hot-reload.js:42:13

The language server seems to be rebuilding on every keystroke and writing to client/build as evidenced by inotifywait:

$ inotifywait --recursive -m client -e close_write
Setting up watches.  Beware: since -r was given, this may take a while!
Watches established.
client/build/ CLOSE_WRITE,CLOSE gleam-lsp-javascript.lock
client/build/ CLOSE_WRITE,CLOSE gleam-lsp-javascript.lock
client/build/ CLOSE_WRITE,CLOSE gleam-lsp-javascript.lock
[ ... continues as I type more, without saving the file ... ]

I feel like the 50ms debouncing added in 925db00 might be too short to be effective in grouping all fs events together?

System info, just in case:

• system: "x86_64-linux"
• host os: Linux 6.18.4, NixOS, 26.05 (Yarara), 26.05.20260111.ffbc9f8
• gleam: 1.14.0
• lustre: 5.5.2
• lustre_dev_tools: 2.3.4
• bun: 1.3.5
• tailwindcss: 4.1.18

And gleam.toml section for the dev tools:

[tools.lustre.bin]
bun = "system"
tailwindcss = "system"

[tools.lustre.build]
minify = true
outdir = "../server/priv/static"

[tools.lustre.dev]
host = "0.0.0.0"
port = 1312
proxy = { from = "/api", to = "http://localhost:1313/api" }
watch_mode = "events"

[hayleigh-dot-dev]

This is unfortunately the tailwind cli misbehaving, with not much we can do about it. Tailwind is supposed to respect .gitignore and not scan those files for builds. Unfortunately when the cli is running in watch mode it still watches everything even if the build does nothing...

We could introduce a similar debounce for the on our side though, so at least the client doesn't get hammered.

[alixinne]

Oh that makes sense. I found some issues related to this, and the solution from this comment seems to do the trick. With the following change to my CSS the issue no longer manifests:

 # client/src/client.css
-@import "tailwindcss";
+@import "tailwindcss" source(".");

As pointed out in the rest of the discussion on that issue, @source not "../build" doesn't work as the CLI is still watching the current directory, unlike when specifying source on the tailwind import statement.

[hayleigh-dot-dev]

Good sleuthing! Very silly this is necessary :')