feat(linter): implement unicorn/prefer-switch

[camc314]

No description provided.

[camc314]

• feat(linter): implement unicorn/prefer-switch #19604 👈 (View in Graphite)
• feat(linter): implement unicorn/prefer-module #19603
• main

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[codspeed-hq]

Merging this PR will not alter performance

✅ 47 untouched benchmarks
⏩ 3 skipped benchmarks¹

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_{Comparing c/02-10-feat_linter_implement_unicorn_prefer-switch (2b0552c) with main (42f78bb)²}

Footnotes

1. 3 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on graphite-base/19604 (d9461a6) during the generation of this report, so main (42f78bb) was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Copilot]

Pull request overview

Implements the eslint-plugin-unicorn(prefer-switch) lint rule in oxc_linter, adding it to the Unicorn rule set and wiring it into the generated rule registries and snapshots.

Changes:

• Added new rule implementation PreferSwitch with configuration parsing and AST analysis for if/else-if chains.
• Registered the rule in rules.rs and the generated rules_enum.rs / rule_runner_impls.rs.
• Added snapshot coverage for rule diagnostics.

Reviewed changes

Copilot reviewed 3 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/oxc_linter/src/rules/unicorn/prefer_switch.rs	New rule implementation + unit tests and snapshot generation.
crates/oxc_linter/src/rules.rs	Exposes the new Unicorn rule module.
crates/oxc_linter/src/generated/rules_enum.rs	Adds the rule to the generated enum/registry plumbing.
crates/oxc_linter/src/generated/rule_runner_impls.rs	Registers the rule runner for IfStatement nodes.
crates/oxc_linter/src/snapshots/unicorn_prefer_switch.snap	New snapshot output for failing test cases.

[Copilot]

PreferSwitchConfig defines empty_default_case (and EmptyDefaultCase) but the rule never reads it, so user configuration has no effect and the option-specific tests don’t actually validate behavior. Either implement the intended behavior gated on self.0.empty_default_case or remove this config field/enum until it’s supported to avoid a misleading public config surface.

Suggested change

	#[derive(Debug, Clone, Copy, Default, Deserialize, JsonSchema)]
	#[serde(rename_all = "kebab-case")]
	pub enum EmptyDefaultCase {
	/// Require a comment in the default case to explain why it's empty.
	#[default]
	NoDefaultComment,
	/// Allow an empty default case.
	DoNothingComment,
	/// Disallow a default case.
	NoDefaultCase,
	}
	#[derive(Debug, Clone, Deserialize, JsonSchema)]
	#[serde(rename_all = "camelCase", default, deny_unknown_fields)]
	pub struct PreferSwitchConfig {
	/// The minimum number of cases required to trigger the rule.
	minimum_cases: usize,
	/// How to handle an empty default case.
	empty_default_case: EmptyDefaultCase,
	}
	impl Default for PreferSwitchConfig {
	fn default() -> Self {
	Self { minimum_cases: 3, empty_default_case: EmptyDefaultCase::NoDefaultComment }
	#[derive(Debug, Clone, Deserialize, JsonSchema)]
	#[serde(rename_all = "camelCase", default, deny_unknown_fields)]
	pub struct PreferSwitchConfig {
	/// The minimum number of cases required to trigger the rule.
	minimum_cases: usize,
	}
	impl Default for PreferSwitchConfig {
	fn default() -> Self {
	Self { minimum_cases: 3 }

[Copilot]

This test case is in the fail list, but with the default minimum_cases of 3 a single if (foo === 1) {} should not trigger the rule (the rule only warns once the chain length reaches minimum_cases). This will cause the test to expect a diagnostic that the current implementation will never emit; move this case to pass or provide a config that lowers minimumCases if you intend it to fail.

Suggested change

	("if (foo === 1) {}", None),
	(
	"if (foo === 1) {}
	else if (foo === 2) {}
	else if (foo === 3) {}
	else if (foo === 4) {}
	(
	"if (foo === 1) {}
	else if (foo === 2) {}
	else if (foo === 3) {}",
	None,
	),