📎 CLI flag in linter to write ignores for existing violations

[anthonyshew]

Description

As described in this discussion and in Discord, it would be great to have an option to write in ignores for existing rule violations.

I stumbled upon the need for this feature while working on migrating a large codebase to Biome. There are rules I'd like to activate that have hundreds and thousands of violations, but I can't reasonably fix them all in one PR. I can use some creative override patterning to get it done, but an easier way would be to set ignores for them and follow up with PRs to fix those ignores. There are likely other use cases for this feature, as well.

I will be starting work on this feature momentarily, having received prior blessings from @ematipico and @Conaclos at that Discord pointer.

Open questions:

• What should we name this? I'm going to use biome lint . --write-suppressions while I work but can name it whatever the crowd prefers.
• Ignoring for Biome is done with // biome-ignore the/rule/name: <explanation>, so I'd like to allow for an explanation with biome lint . --write-suppressions="TODO: Fix Biome migration ignores.", where my string would become the <explanation>. If not provided, a default explanation will be provided (or we could just let it be <explanation>?). Any thoughts here on what to provide for a default? And does that API sound good?
• I've only minimally poked around the codebase at this point so codepointers/prior art on how to implement this would be helpful, especially if there is a specific way that sounds preferable to the project maintainers. Otherwise, I'll just have at it. 😄

[dyc3]

I personally don't have any problems with the --write-suppressions="TODO: message" flag. IMO, that's about as good as its gonna get. This will definitely be super valuable for migrating. My only suggestion is that there be a default message if none is provided, something to indicate it was automatically generated.

As for code pointers, I don't have perfect context on how suppressions are implemented. But from just a quick look around, I don't think it will be that difficult. You'll probably want to look at:

• The Rule trait's suppress method, because we already have a LSP code action to suppress lints. (this is probably the most useful one) https://github.com/biomejs/biome/blob/76a4f1a0ac4cfa63244d19c1f8c18a2defbc920b/crates/biome_analyze/src/rule.rs#L868
• biome_analyze::handle_comment()
• the biome_suppression crate (as comment syntaxes are in there)
• maybe SuppressionAction::find_token_to_apply_suppression()