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feat(linter): add full TS support to eslint/no-useless-constructor #17592

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Merged
graphite-app merged 1 commit into from
Jan 2, 2026
Merged

feat(linter): add full TS support to eslint/no-useless-constructor #17592

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297 changes: 288 additions & 9 deletions crates/oxc_linter/src/rules/eslint/no_useless_constructor.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use oxc_ast::{
AstKind,
ast::{
Argument, BindingPattern, CallExpression, Expression, FormalParameter, FormalParameterRest,
Argument, BindingPattern, CallExpression, Expression, FormalParameterRest,
FormalParameters, FunctionBody, MethodDefinition, Statement, TSAccessibility,
},
};
Expand Down Expand Up @@ -112,19 +112,23 @@ impl Rule for NoUselessConstructor {
let Some(body) = &constructor.value.body else {
return;
};
// allow `private private constructor() {}`. However, `public private
// constructor() {}` is the same as `constructor() {}` and so is not allowed.
if constructor.accessibility.is_some_and(|access| {
matches!(access, TSAccessibility::Private | TSAccessibility::Protected)
}) {
return;
}

let class = ctx.nodes().ancestors(node.id()).find_map(|parent| parent.kind().as_class());
debug_assert!(class.is_some(), "Found a constructor outside of a class definition");
let Some(class) = class else {
return;
};

match &constructor.accessibility {
Some(TSAccessibility::Private | TSAccessibility::Protected) => {
return;
}
Some(TSAccessibility::Public) if class.super_class.is_some() => {
return;
}
_ => {}
}

if class.declare {
return;
}
Expand All @@ -149,7 +153,13 @@ fn lint_empty_constructor<'a>(

// allow constructors with parameter properties since they actually declare
// class members
if constructor.value.params.items.iter().any(FormalParameter::has_modifier) {
if constructor
.value
.params
.items
.iter()
.any(|param| param.has_modifier() || !param.decorators.is_empty())
{
return;
}

Expand All @@ -172,6 +182,7 @@ fn lint_redundant_super_call<'a>(

if is_only_simple_params(params)
&& !is_overriding(params)
&& !has_decorated_params(params)
&& (is_spread_arguments(super_args) || is_passing_through(params, super_args))
{
ctx.diagnostic_with_fix(
Expand All @@ -185,6 +196,10 @@ fn is_overriding(params: &FormalParameters) -> bool {
params.items.iter().any(|param| param.r#override)
}

fn has_decorated_params(params: &FormalParameters) -> bool {
params.items.iter().any(|param| !param.decorators.is_empty())
}

/// Check if a function body only contains a single `super()` call. Ignores directives.
///
/// Returns the call expression if the body contains a single `super()` call, otherwise [`None`].
Expand Down Expand Up @@ -324,6 +339,205 @@ fn test() {
// ",
];

let pass_typescript = vec![
"class A {}",
"
class A {
constructor() {
doSomething();
}
}
",
"
class A extends B {
constructor() {}
}
",
"
class A extends B {
constructor() {
super('foo');
}
}
",
"
class A extends B {
constructor(foo, bar) {
super(foo, bar, 1);
}
}
",
"
class A extends B {
constructor() {
super();
doSomething();
}
}
",
"
class A extends B {
constructor(...args) {
super(...args);
doSomething();
}
}
",
"
class A {
dummyMethod() {
doSomething();
}
}
",
"
class A extends B.C {
constructor() {
super(foo);
}
}
",
"
class A extends B.C {
constructor([a, b, c]) {
super(...arguments);
}
}
",
"
class A extends B.C {
constructor(a = f()) {
super(...arguments);
}
}
",
"
class A extends B {
constructor(a, b, c) {
super(a, b);
}
}
",
"
class A extends B {
constructor(foo, bar) {
super(foo);
}
}
",
"
class A extends B {
constructor(test) {
super();
}
}
",
"
class A extends B {
constructor() {
foo;
}
}
",
"
class A extends B {
constructor(foo, bar) {
super(bar);
}
}
",
"
declare class A {
constructor();
}
",
"
class A {
constructor();
}
",
"
abstract class A {
constructor();
}
",
"
class A {
constructor(private name: string) {}
}
",
"
class A {
constructor(public name: string) {}
}
",
"
class A {
constructor(protected name: string) {}
}
",
"
class A {
private constructor() {}
}
",
"
class A {
protected constructor() {}
}
",
"
class A extends B {
public constructor() {}
}
",
"
class A extends B {
protected constructor(foo, bar) {
super(bar);
}
}
",
"
class A extends B {
private constructor(foo, bar) {
super(bar);
}
}
",
"
class A extends B {
public constructor(foo) {
super(foo);
}
}
",
"
class A extends B {
public constructor(foo) {}
}
",
"
class A {
constructor(foo);
}
",
"
class A extends Object {
constructor(@Foo foo: string) {
super(foo);
}
}
",
"
class A extends Object {
constructor(foo: string, @Bar() bar) {
super(foo, bar);
}
}
",
];

let fail = vec![
"class A { constructor(){} }",
"class A { 'constructor'(){} }",
Expand All @@ -343,6 +557,68 @@ fn test() {
"class A { public constructor(){} }",
];

let fail_typescript = vec![
"
class A {
constructor() {}
}
",
"
class A extends B {
constructor() {
super();
}
}
",
"
class A extends B {
constructor(foo) {
super(foo);
}
}
",
"
class A extends B {
constructor(foo, bar) {
super(foo, bar);
}
}
",
"
class A extends B {
constructor(...args) {
super(...args);
}
}
",
"
class A extends B.C {
constructor() {
super(...arguments);
}
}
",
"
class A extends B {
constructor(a, b, ...c) {
super(...arguments);
}
}
",
"
class A extends B {
constructor(a, b, ...c) {
super(a, b, ...c);
}
}
",
"
class A {
public constructor() {}
}
",
];

let fix = vec![
("class A { constructor(){} }", "class A { }"),
(
Expand All @@ -351,6 +627,9 @@ fn test() {
),
];

let pass = [pass, pass_typescript].concat();
let fail = [fail, fail_typescript].concat();

Tester::new(NoUselessConstructor::NAME, NoUselessConstructor::PLUGIN, pass, fail)
.expect_fix(fix)
.test_and_snapshot();
Expand Down
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