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feat(linter): support countVoidThis option in max-params rule #12604

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merged 1 commit into from
Jul 30, 2025
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feat(linter): support countVoidThis option in max-params rule #12604

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81 changes: 71 additions & 10 deletions crates/oxc_linter/src/rules/eslint/max_params.rs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
use oxc_ast::AstKind;
use oxc_ast::{AstKind, ast::TSType};
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::Span;
Expand All @@ -20,6 +20,7 @@ pub struct MaxParams(Box<MaxParamsConfig>);
#[derive(Debug, Clone)]
pub struct MaxParamsConfig {
max: usize,
count_void_this: bool,
}

impl std::ops::Deref for MaxParams {
Expand All @@ -32,7 +33,7 @@ impl std::ops::Deref for MaxParams {

impl Default for MaxParamsConfig {
fn default() -> Self {
Self { max: 3 }
Self { max: 3, count_void_this: false }
}
}

Expand Down Expand Up @@ -88,6 +89,15 @@ declare_oxc_lint!(
///
/// For example `{ "max": 4 }` would mean that having a function take four
/// parameters is allowed which overrides the default of three.
///
/// ### countVoidThis
///
/// `{ "countVoidThis": boolean }`
///
/// This option is for counting the `this` parameter if it is of type `void`.
///
/// For example `{ "countVoidThis": true }` would mean that having a function
/// take a `this` parameter of type `void` is counted towards the maximum number of parameters.
MaxParams,
eslint,
style
Expand All @@ -101,15 +111,19 @@ impl Rule for MaxParams {
.and_then(serde_json::Number::as_u64)
.and_then(|v| usize::try_from(v).ok())
{
Self(Box::new(MaxParamsConfig { max }))
Self(Box::new(MaxParamsConfig { max, count_void_this: false }))
} else {
let max = config
.and_then(|config| config.get("max"))
.and_then(Value::as_number)
.and_then(serde_json::Number::as_u64)
.map_or(3, |v| usize::try_from(v).unwrap_or(3));
let count_void_this = config
.and_then(|config| config.get("countVoidThis"))
.and_then(Value::as_bool)
.unwrap_or(false);

Self(Box::new(MaxParamsConfig { max }))
Self(Box::new(MaxParamsConfig { max, count_void_this }))
}
}

Expand All @@ -119,23 +133,31 @@ impl Rule for MaxParams {
if !function.is_declaration() & !function.is_expression() {
return;
}
let params = &function.params;
let mut real_len = params.items.len();
if let Some(this_params) = &function.this_param {
let is_void_this = this_params
.type_annotation
.as_ref()
.is_some_and(|t| matches!(t.type_annotation, TSType::TSVoidKeyword(_)));
if self.count_void_this || !is_void_this {
real_len += 1;
}
}

if function.params.items.len() > self.max {
if real_len > self.max {
if let Some(id) = &function.id {
let function_name = id.name.as_str();
let error_msg = format!(
"Function '{}' has too many parameters ({}). Maximum allowed is {}.",
function_name,
function.params.items.len(),
self.max
function_name, real_len, self.max
);
let span = function.params.span;
ctx.diagnostic(max_params_diagnostic(&error_msg, span));
} else {
let error_msg = format!(
"Function has too many parameters ({}). Maximum allowed is {}.",
function.params.items.len(),
self.max
real_len, self.max
);
let span = function.params.span;
ctx.diagnostic(max_params_diagnostic(&error_msg, span));
Expand Down Expand Up @@ -168,6 +190,23 @@ fn test() {
("var test = (a, b, c) => {};", Some(serde_json::json!([3]))),
("var test = function test(a, b, c) {};", Some(serde_json::json!([3]))),
("var test = function(a, b, c) {};", Some(serde_json::json!([{ "max": 3 }]))),
(
"function testD(this: void, a) {}",
Some(serde_json::json!([{ "max": 2, "countVoidThis": true }])),
),
(
"function testD(this: void, a, b) {}",
Some(serde_json::json!([{ "max": 2, "countVoidThis": false }])),
),
("const testE = function (this: void, a) {}", Some(serde_json::json!([1]))),
(
"const testE = function (this: void, a) {}",
Some(serde_json::json!([{ "max": 2, "countVoidThis": false }])),
),
(
"const testE = function (this: any, a) {}",
Some(serde_json::json!([{ "max": 2, "countVoidThis": true }])),
),
];

let fail = vec![
Expand All @@ -186,6 +225,28 @@ fn test() {
}",
Some(serde_json::json!([{ "max": 2 }])),
),
(
"function testD(this: void, a, b) {}",
Some(serde_json::json!([{ "max": 2, "countVoidThis": true }])),
),
(
"
class Foo { method(this: void, a) {} }
",
Some(serde_json::json!([{ "max": 1, "countVoidThis": true }])),
),
(
"const testE = function (this: void, a) {}",
Some(serde_json::json!([{ "max": 1, "countVoidThis": true }])),
),
(
"const testE = function (this: any, a) {}",
Some(serde_json::json!([{ "max": 1, "countVoidThis": true }])),
),
(
"const testE = function (this: any, a) {}",
Some(serde_json::json!([{ "max": 1, "countVoidThis": false }])),
),
];

Tester::new(MaxParams::NAME, MaxParams::PLUGIN, pass, fail).test_and_snapshot();
Expand Down
37 changes: 37 additions & 0 deletions crates/oxc_linter/src/snapshots/eslint_max_params.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -71,3 +71,40 @@ source: crates/oxc_linter/src/tester.rs
2 │ // Just to make it longer
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.

⚠ eslint(max-params): Function 'testD' has too many parameters (3). Maximum allowed is 2.
╭─[max_params.tsx:1:15]
1 │ function testD(this: void, a, b) {}
· ──────────────────
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.

⚠ eslint(max-params): Function has too many parameters (2). Maximum allowed is 1.
╭─[max_params.tsx:2:35]
1 │
2 │ class Foo { method(this: void, a) {} }
· ───────────────
3 │
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.

⚠ eslint(max-params): Function has too many parameters (2). Maximum allowed is 1.
╭─[max_params.tsx:1:24]
1 │ const testE = function (this: void, a) {}
· ───────────────
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.

⚠ eslint(max-params): Function has too many parameters (2). Maximum allowed is 1.
╭─[max_params.tsx:1:24]
1 │ const testE = function (this: any, a) {}
· ──────────────
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.

⚠ eslint(max-params): Function has too many parameters (2). Maximum allowed is 1.
╭─[max_params.tsx:1:24]
1 │ const testE = function (this: any, a) {}
· ──────────────
╰────
help: This rule enforces a maximum number of parameters allowed in function definitions.
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