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feat(linter): implement eslint/vars-on-top (#8157)

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implement: https://eslint.org/docs/latest/rules/vars-on-top
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Yuichiro Yamashita 2024-12-30 02:13:45 +09:00 committed by GitHub
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2
crates/oxc_linter/src/rules.rs
View file

@ -154,6 +154,7 @@ mod eslint {
pub mod unicode_bom; pub mod unicode_bom;
pub mod use_isnan; pub mod use_isnan;
pub mod valid_typeof; pub mod valid_typeof;
pub mod vars_on_top;
pub mod yoda; pub mod yoda;
} }
@ -647,6 +648,7 @@ oxc_macros::declare_all_lint_rules! {
eslint::unicode_bom, eslint::unicode_bom,
eslint::use_isnan, eslint::use_isnan,
eslint::valid_typeof, eslint::valid_typeof,
eslint::vars_on_top,
eslint::yoda, eslint::yoda,
import::default, import::default,
import::export, import::export,

544
crates/oxc_linter/src/rules/eslint/vars_on_top.rs Normal file
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@ -0,0 +1,544 @@
use oxc_ast::ast::{Declaration, Expression, Program, Statement, VariableDeclarationKind};
use oxc_ast::AstKind;
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::{GetSpan, Span};
use crate::{context::LintContext, rule::Rule, AstNode};
fn vars_on_top_diagnostic(span: Span) -> OxcDiagnostic {
OxcDiagnostic::warn("All 'var' declarations must be at the top of the function scope.")
.with_help("Consider moving this to the top of the functions scope or using let or const to declare this variable.")
.with_label(span)
}
#[derive(Debug, Default, Clone)]
pub struct VarsOnTop;
declare_oxc_lint!(
/// ### What it does
///
/// Enforces that all `var` declarations are placed at the top of their containing scope.
///
/// ### Why is this bad?
///
/// In JavaScript, `var` declarations are hoisted to the top of their containing scope. Placing `var` declarations at the top explicitly improves code readability and maintainability by making the scope of variables clear.
///
/// ### Examples
///
/// Examples of **incorrect** code for this rule:
/// ```js
/// function doSomething() {
/// if (true) {
/// var first = true;
/// }
/// var second;
/// }
///
/// function doSomethingElse() {
/// for (var i = 0; i < 10; i++) {}
/// }
///
/// f();
/// var a;
///
/// class C {
/// static {
/// if (something) {
/// var a = true;
/// }
/// }
/// static {
/// f();
/// var a;
/// }
/// }
/// ```
///
/// Examples of **correct** code for this rule:
/// ```js
/// function doSomething() {
/// var first;
/// var second;
/// if (true) {
/// first = true;
/// }
/// }
///
/// function doSomethingElse() {
/// var i;
/// for (i = 0; i < 10; i++) {}
/// }
///
/// var a;
/// f();
///
/// class C {
/// static {
/// var a;
/// if (something) {
/// a = true;
/// }
/// }
/// static {
/// var a;
/// f();
/// }
/// }
/// ```
VarsOnTop,
style,
);
impl Rule for VarsOnTop {
fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
let AstKind::VariableDeclaration(declaration) = node.kind() else {
return;
};
if declaration.kind != VariableDeclarationKind::Var {
return;
}
let Some(parent) = ctx.nodes().parent_node(node.id()) else {
return;
};
match parent.kind() {
AstKind::ExportNamedDeclaration(_) => {
if let Some(grand_parent) = ctx.nodes().parent_node(parent.id()) {
if let AstKind::Program(grand_parent) = grand_parent.kind() {
global_var_check(parent, grand_parent, ctx);
}
}
}
AstKind::Program(parent) => {
global_var_check(node, parent, ctx);
}
_ => block_scope_var_check(node, ctx),
}
}
}
fn looks_like_directive(node: &Statement) -> bool {
matches!(
node,
Statement::ExpressionStatement(expr_stmt) if matches!(
&expr_stmt.expression,
Expression::StringLiteral(_)
)
)
}
fn looks_like_import(node: &Statement) -> bool {
matches!(node, Statement::ImportDeclaration(_))
}
fn is_variable_declaration(node: &Statement) -> bool {
if matches!(node, Statement::VariableDeclaration(_)) {
return true;
}
if let Statement::ExportNamedDeclaration(export) = node {
return matches!(export.declaration, Some(Declaration::VariableDeclaration(_)));
}
false
}
fn is_var_on_top(node: &AstNode, statements: &[Statement], ctx: &LintContext) -> bool {
let mut i = 0;
let len = statements.len();
let parent = ctx.nodes().parent_node(node.id());
if let Some(parent) = parent {
if !matches!(parent.kind(), AstKind::StaticBlock(_)) {
while i < len {
if !looks_like_directive(&statements[i]) && !looks_like_import(&statements[i]) {
break;
}
i += 1;
}
}
}
let node_span = node.span();
while i < len {
if !is_variable_declaration(&statements[i]) {
return false;
}
let stmt_span = statements[i].span();
if stmt_span == node_span {
return true;
}
i += 1;
}
false
}
fn global_var_check(node: &AstNode, parent: &Program, ctx: &LintContext) {
if !is_var_on_top(node, &parent.body, ctx) {
ctx.diagnostic(vars_on_top_diagnostic(node.span()));
}
}
fn block_scope_var_check(node: &AstNode, ctx: &LintContext) {
if let Some(parent) = ctx.nodes().parent_node(node.id()) {
match parent.kind() {
AstKind::BlockStatement(block) => {
if check_var_on_top_in_function_scope(node, &block.body, parent, ctx) {
return;
}
}
AstKind::FunctionBody(block) => {
if check_var_on_top_in_function_scope(node, &block.statements, parent, ctx) {
return;
}
}
AstKind::StaticBlock(block) => {
if is_var_on_top(node, &block.body, ctx) {
return;
}
}
_ => {}
}
}
ctx.diagnostic(vars_on_top_diagnostic(node.span()));
}
fn check_var_on_top_in_function_scope(
node: &AstNode,
statements: &[Statement],
parent: &AstNode,
ctx: &LintContext,
) -> bool {
if let Some(grandparent) = ctx.nodes().parent_node(parent.id()) {
if matches!(
grandparent.kind(),
AstKind::Function(_) | AstKind::FunctionBody(_) | AstKind::ArrowFunctionExpression(_)
) && is_var_on_top(node, statements, ctx)
{
return true;
}
}
false
}
#[test]
fn test() {
use crate::tester::Tester;
let pass = vec![
"var first = 0;
function foo() {
first = 2;
}
",
"function foo() {
}
",
"function foo() {
var first;
if (true) {
first = true;
} else {
first = 1;
}
}
",
"function foo() {
var first;
var second = 1;
var third;
var fourth = 1, fifth, sixth = third;
var seventh;
if (true) {
third = true;
}
first = second;
}
",
"function foo() {
var i;
for (i = 0; i < 10; i++) {
alert(i);
}
}
",
"function foo() {
var outer;
function inner() {
var inner = 1;
var outer = inner;
}
outer = 1;
}
",
"function foo() {
var first;
//Hello
var second = 1;
first = second;
}
",
"function foo() {
var first;
/*
Hello Clarice
*/
var second = 1;
first = second;
}
",
"function foo() {
var first;
var second = 1;
function bar(){
var first;
first = 5;
}
first = second;
}
",
"function foo() {
var first;
var second = 1;
function bar(){
var third;
third = 5;
}
first = second;
}
",
"function foo() {
var first;
var bar = function(){
var third;
third = 5;
}
first = 5;
}
",
"function foo() {
var first;
first.onclick(function(){
var third;
third = 5;
});
first = 5;
}
",
"function foo() {
var i = 0;
for (let j = 0; j < 10; j++) {
alert(j);
}
i = i + 1;
}", // { "ecmaVersion": 6 },
"'use strict'; var x; f();",
"'use strict'; 'directive'; var x; var y; f();",
"function f() { 'use strict'; var x; f(); }",
"function f() { 'use strict'; 'directive'; var x; var y; f(); }",
"import React from 'react'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"'use strict'; import React from 'react'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import React from 'react'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import * as foo from 'mod.js'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import { square, diag } from 'lib'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import { default as foo } from 'lib'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import 'src/mylib'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"import theDefault, { named1, named2 } from 'src/mylib'; 'use strict'; var y; function f() { 'use strict'; var x; var y; f(); }", // { "ecmaVersion": 6, "sourceType": "module" },
"export var x;
var y;
var z;", // { "ecmaVersion": 6, "sourceType": "module" },
"var x;
export var y;
var z;", // { "ecmaVersion": 6, "sourceType": "module" },
"var x;
var y;
export var z;", // { "ecmaVersion": 6, "sourceType": "module" },
"class C {
static {
var x;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
var x;
foo();
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
var x;
var y;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
var x;
var y;
foo();
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
let x;
var y;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
foo();
let x;
}
}", // { "ecmaVersion": 2022 }
];
let fail = vec![
"var first = 0;
function foo() {
first = 2;
second = 2;
}
var second = 0;",
"function foo() {
var first;
first = 1;
first = 2;
first = 3;
first = 4;
var second = 1;
second = 2;
first = second;
}",
"function foo() {
var first;
if (true) {
var second = true;
}
first = second;
}",
"function foo() {
for (var i = 0; i < 10; i++) {
alert(i);
}
}",
"function foo() {
var first = 10;
var i;
for (i = 0; i < first; i ++) {
var second = i;
}
}",
"function foo() {
var first = 10;
var i;
switch (first) {
case 10:
var hello = 1;
break;
}
}",
"function foo() {
var first = 10;
var i;
try {
var hello = 1;
} catch (e) {
alert('error');
}
}",
"function foo() {
var first = 10;
var i;
try {
asdf;
} catch (e) {
var hello = 1;
}
}",
"function foo() {
var first = 10;
while (first) {
var hello = 1;
}
}",
"function foo() {
var first = 10;
do {
var hello = 1;
} while (first == 10);
}",
"function foo() {
var first = [1,2,3];
for (var item in first) {
item++;
}
}",
"function foo() {
var first = [1,2,3];
var item;
for (item in first) {
var hello = item;
}
}",
"var foo = () => {
var first = [1,2,3];
var item;
for (item in first) {
var hello = item;
}
}", // { "ecmaVersion": 6 },
"'use strict'; 0; var x; f();",
"'use strict'; var x; 'directive'; var y; f();",
"function f() { 'use strict'; 0; var x; f(); }",
"function f() { 'use strict'; var x; 'directive'; var y; f(); }",
"export function f() {}
var x;", // { "ecmaVersion": 6, "sourceType": "module" },
"var x;
export function f() {}
var y;", // { "ecmaVersion": 6, "sourceType": "module" },
"import {foo} from 'foo';
export {foo};
var test = 1;", // { "ecmaVersion": 6, "sourceType": "module" },
"export {foo} from 'foo';
var test = 1;", // { "ecmaVersion": 6, "sourceType": "module" },
"export * from 'foo';
var test = 1;", // { "ecmaVersion": 6, "sourceType": "module" },
"class C {
static {
foo();
var x;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
'use strict';
var x;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
var x;
foo();
var y;
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
if (foo) {
var x;
}
}
}", // { "ecmaVersion": 2022 },
"class C {
static {
if (foo)
var x;
}
}", // { "ecmaVersion": 2022 }
];
Tester::new(VarsOnTop::NAME, VarsOnTop::CATEGORY, pass, fail).test_and_snapshot();
}

232
crates/oxc_linter/src/snapshots/eslint_vars_on_top.snap Normal file
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@ -0,0 +1,232 @@
---
source: crates/oxc_linter/src/tester.rs
snapshot_kind: text
---
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:6:4]
5 │ }
6 │ var second = 0;
· ───────────────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:7:7]
6 │ first = 4;
7 │ var second = 1;
· ───────────────
8 │ second = 2;
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:11]
3 │ if (true) {
4 │ var second = true;
· ──────────────────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:2:12]
1 │ function foo() {
2 │ for (var i = 0; i < 10; i++) {
· ─────────
3 │ alert(i);
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:5:11]
4 │ for (i = 0; i < first; i ++) {
5 │ var second = i;
· ───────────────
6 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:6:15]
5 │ case 10:
6 │ var hello = 1;
· ──────────────
7 │ break;
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:5:11]
4 │ try {
5 │ var hello = 1;
· ──────────────
6 │ } catch (e) {
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:7:11]
6 │ } catch (e) {
7 │ var hello = 1;
· ──────────────
8 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:11]
3 │ while (first) {
4 │ var hello = 1;
· ──────────────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:11]
3 │ do {
4 │ var hello = 1;
· ──────────────
5 │ } while (first == 10);
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:3:12]
2 │ var first = [1,2,3];
3 │ for (var item in first) {
· ────────
4 │ item++;
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:5:11]
4 │ for (item in first) {
5 │ var hello = item;
· ─────────────────
6 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:5:11]
4 │ for (item in first) {
5 │ var hello = item;
· ─────────────────
6 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:1:18]
1 │ 'use strict'; 0; var x; f();
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:1:35]
1 │ 'use strict'; var x; 'directive'; var y; f();
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:1:33]
1 │ function f() { 'use strict'; 0; var x; f(); }
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:1:51]
1 │ function f() { 'use strict'; var x; 'directive'; var y; f(); }
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:2:4]
1 │ export function f() {}
2 │ var x;
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:3:4]
2 │ export function f() {}
3 │ var y;
· ──────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:3:4]
2 │ export {foo};
3 │ var test = 1;
· ─────────────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:2:4]
1 │ export {foo} from 'foo';
2 │ var test = 1;
· ─────────────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:2:4]
1 │ export * from 'foo';
2 │ var test = 1;
· ─────────────
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:12]
3 │ foo();
4 │ var x;
· ──────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:12]
3 │ 'use strict';
4 │ var x;
· ──────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:5:12]
4 │ foo();
5 │ var y;
· ──────
6 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:16]
3 │ if (foo) {
4 │ var x;
· ──────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
╭─[vars_on_top.tsx:4:16]
3 │ if (foo)
4 │ var x;
· ──────
5 │ }
╰────
help: Consider moving this to the top of the functions scope or using let or const to declare this variable.