💅 Svelte Reactive Blocks marked as Unexpected/Unused

[helloimalastair]

Environment information

CLI:
  Version:                      1.7.1
  Color support:                true

Platform:
  CPU Architecture:             aarch64
  OS:                           macos

Environment:
  BIOME_LOG_DIR:                unset
  NO_COLOR:                     unset
  TERM:                         "xterm-256color"
  JS_RUNTIME_VERSION:           "v21.7.3"
  JS_RUNTIME_NAME:              "node"
  NODE_PACKAGE_MANAGER:         "pnpm/9.0.5"

Biome Configuration:
  Status:                       Loaded successfully
  Formatter disabled:           false
  Linter disabled:              false
  Organize imports disabled:    false
  VCS disabled:                 false

Linter:
  Recommended:                  true
  All:                          false
  Rules:
Workspace:
  Open Documents:               0

Rule names

lint/suspicious/noConfusingLabels, lint/correctness/noUnusedLabels

Playground link

https://biomejs.dev/playground/?code=JAA6ACAAewAKACAAIABjAG8AbgBzAG8AbABlAC4AbABvAGcAKAAiAEkAJwBtACAAaQBuACAAYQAgAHIAZQBhAGMAdABpAHYAZQAgAGIAbABvAGMAawAhACIAKQAKAH0A

Expected result

While in a Svelte Code Block, a Reactive Block

$: {
	console.log(someData);
};

can be defined, which will trigger whenever its variables change. In this case, Biome is marking the $ symbol as an Unepected/Unused label, which can cause it to be removed with --apply.

I would expect the $ symbol to be an allowed symbol in the context of Svelte Code Blocks, and thus allowed to exist.

Code of Conduct

• I agree to follow Biome's Code of Conduct

[ematipico]

We have two options here:

• Document the caveat on the website, and tell people to disable the rules themselves;
• We start disabling rules based on file extension. For example, we would need to disable other rules for other files, such as noUnusedVariables for Astro files. And noUnusedImports for all vue/astro/svelte files

[Conaclos]

We start disabling rules based on file extension. For example, we would need to disable other rules for other files, such as noUnusedVariables for Astro files. And noUnusedImports for all vue/astro/svelte files

One caveat of this approach is that users cannot enable a rule if they want to.

I see a third approach: providing a default config file where we have an overrides that disable some rules for a given extension.

[ematipico]

One caveat of this approach is that users cannot enable a rule if they want to.

how would a user need to use a rule that triggers false positives?

[Conaclos]

how would a user need to use a rule that triggers false positives?

Because all labels are not labels that indicate a reactive statement?
We completely lose the interest of the rule.

I think a better strategy is just ignoring labels named $ in svelte components.
This is what I did in #2692

[ematipico]

Fair point