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refactor(linter): improve eslint/no-redeclare #9976

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graphite-app merged 1 commit into from
Mar 23, 2025
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refactor(linter): improve eslint/no-redeclare #9976

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107 changes: 55 additions & 52 deletions crates/oxc_linter/src/rules/eslint/no_redeclare.rs
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Original file line number Diff line number Diff line change
@@ -1,28 +1,21 @@
use oxc_ast::{
AstKind,
ast::{BindingIdentifier, BindingPatternKind},
};
use javascript_globals::GLOBALS;
use oxc_diagnostics::OxcDiagnostic;
use oxc_macros::declare_oxc_lint;
use oxc_span::Span;
use oxc_syntax::symbol::SymbolId;

use crate::{context::LintContext, rule::Rule};

fn no_redeclare_diagnostic(id_name: &str, decl_span: Span, re_decl_span: Span) -> OxcDiagnostic {
OxcDiagnostic::warn(format!("'{id_name}' is already defined.")).with_labels([
decl_span.label(format!("'{id_name}' is already defined.")),
fn no_redeclare_diagnostic(name: &str, decl_span: Span, re_decl_span: Span) -> OxcDiagnostic {
OxcDiagnostic::warn(format!("'{name}' is already defined.")).with_labels([
decl_span.label(format!("'{name}' is already defined.")),
re_decl_span.label("It can not be redeclare here."),
])
}

fn no_redeclare_as_builtin_in_diagnostic(builtin_name: &str, span: Span) -> OxcDiagnostic {
OxcDiagnostic::warn(format!(
"'{builtin_name}' is already defined as a built-in global variable."
))
.with_label(
span.label(format!("'{builtin_name}' is already defined as a built-in global variable.")),
)
fn no_redeclare_as_builtin_in_diagnostic(name: &str, span: Span) -> OxcDiagnostic {
OxcDiagnostic::warn(format!("'{name}' is already defined as a built-in global variable."))
.with_label(span)
}

#[derive(Debug, Default, Clone)]
Expand All @@ -33,17 +26,35 @@ pub struct NoRedeclare {
declare_oxc_lint!(
/// ### What it does
///
/// Disallow variable redeclaration
/// This rule disallows redeclaring variables within the same scope, ensuring that each variable
/// is declared only once. It helps avoid confusion and unintended behavior in code.
///
/// ### Why is this bad?
///
/// n JavaScript, it’s possible to redeclare the same variable name using var. This can lead to confusion as to where the variable is actually declared and initialized.
/// Redeclaring variables in the same scope can lead to unexpected behavior, overwriting existing values,
/// and making the code harder to understand and maintain.
///
/// ### Example
/// ### Examples
///
/// Examples of **incorrect** code for this rule:
/// ```javascript
/// var a = 3;
/// var a = 10;
/// ```
///
/// Examples of **correct** code for this rule:
/// ```javascript
/// var a = 3;
/// a = 10;
/// ```
///
/// ### Options
///
/// #### builtinGlobals
///
/// `{ type: bool, default: false }`
///
/// When set `true`, it flags redeclaring built-in globals (e.g., `let Object = 1;`).
NoRedeclare,
eslint,
pedantic
Expand All @@ -61,40 +72,22 @@ impl Rule for NoRedeclare {
}

fn run_on_symbol(&self, symbol_id: SymbolId, ctx: &LintContext) {
let symbol_table = ctx.scoping();
let decl_node_id = symbol_table.symbol_declaration(symbol_id);
match ctx.nodes().kind(decl_node_id) {
AstKind::VariableDeclarator(var) => {
if let BindingPatternKind::BindingIdentifier(ident) = &var.id.kind {
let symbol_name = symbol_table.symbol_name(symbol_id);
if symbol_name == ident.name.as_str() {
for span in ctx.scoping().symbol_redeclarations(symbol_id) {
self.report_diagnostic(ctx, *span, ident);
}
}
}
}
AstKind::FormalParameter(param) => {
if let BindingPatternKind::BindingIdentifier(ident) = &param.pattern.kind {
let symbol_name = symbol_table.symbol_name(symbol_id);
if symbol_name == ident.name.as_str() {
for span in ctx.scoping().symbol_redeclarations(symbol_id) {
self.report_diagnostic(ctx, *span, ident);
}
}
}
}
_ => {}
let name = ctx.scoping().symbol_name(symbol_id);
let is_builtin = self.built_in_globals
&& (GLOBALS["builtin"].contains_key(name) || ctx.globals().is_enabled(name));

let decl_span = ctx.scoping().symbol_span(symbol_id);

if is_builtin {
ctx.diagnostic(no_redeclare_as_builtin_in_diagnostic(name, decl_span));
}
}
}

impl NoRedeclare {
fn report_diagnostic(&self, ctx: &LintContext, span: Span, ident: &BindingIdentifier) {
if self.built_in_globals && ctx.env_contains_var(&ident.name) {
ctx.diagnostic(no_redeclare_as_builtin_in_diagnostic(ident.name.as_str(), ident.span));
} else {
ctx.diagnostic(no_redeclare_diagnostic(ident.name.as_str(), ident.span, span));
for span in ctx.scoping().symbol_redeclarations(symbol_id) {
if is_builtin {
ctx.diagnostic(no_redeclare_as_builtin_in_diagnostic(name, *span));
} else {
ctx.diagnostic(no_redeclare_diagnostic(name, decl_span, *span));
}
}
}
}
Expand Down Expand Up @@ -144,21 +137,31 @@ fn test() {
("class C { static { var a; { var a; } } }", None),
("class C { static { { var a; } var a; } }", None),
("class C { static { { var a; } { var a; } } }", None),
// ("var Object = 0;", Some(serde_json::json!([{ "builtinGlobals": true }]))),
(
"var Object = 0; var Object = 0; var globalThis = 0;",
Some(serde_json::json!([{ "builtinGlobals": true }])),
),
(
"var a; var {a = 0, b: Object = 0} = {};",
Some(serde_json::json!([{ "builtinGlobals": true }])),
),
// ("var globalThis = 0;", Some(serde_json::json!([{ "builtinGlobals": true }]))),
(
"var a; var {a = 0, b: globalThis = 0} = {};",
Some(serde_json::json!([{ "builtinGlobals": true }])),
),
("function f() { var a; var a; }", None),
("function f(a) { var a; }", None),
("function f(a, b = 1) { var a; var b;}", None),
("function f() { var a; if (test) { var a; } }", None),
("for (var a, a;;);", None),
];

Tester::new(NoRedeclare::NAME, NoRedeclare::PLUGIN, pass, fail).test_and_snapshot();

let fail = vec![(
"var foo;",
Some(serde_json::json!([{ "builtinGlobals": true }])),
Some(serde_json::json!({ "globals": { "foo": false }})),
)];

Tester::new(NoRedeclare::NAME, NoRedeclare::PLUGIN, vec![], fail).test();
}
44 changes: 41 additions & 3 deletions crates/oxc_linter/src/snapshots/eslint_no_redeclare.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -123,6 +123,24 @@ source: crates/oxc_linter/src/tester.rs
· ╰── 'a' is already defined.
╰────

⚠ eslint(no-redeclare): 'Object' is already defined as a built-in global variable.
╭─[no_redeclare.tsx:1:5]
1 │ var Object = 0; var Object = 0; var globalThis = 0;
· ──────
╰────

⚠ eslint(no-redeclare): 'Object' is already defined as a built-in global variable.
╭─[no_redeclare.tsx:1:21]
1 │ var Object = 0; var Object = 0; var globalThis = 0;
· ──────
╰────

⚠ eslint(no-redeclare): 'globalThis' is already defined as a built-in global variable.
╭─[no_redeclare.tsx:1:37]
1 │ var Object = 0; var Object = 0; var globalThis = 0;
· ──────────
╰────

⚠ eslint(no-redeclare): 'a' is already defined.
╭─[no_redeclare.tsx:1:5]
1 │ var a; var {a = 0, b: Object = 0} = {};
Expand All @@ -131,6 +149,12 @@ source: crates/oxc_linter/src/tester.rs
· ╰── 'a' is already defined.
╰────

⚠ eslint(no-redeclare): 'Object' is already defined as a built-in global variable.
╭─[no_redeclare.tsx:1:23]
1 │ var a; var {a = 0, b: Object = 0} = {};
· ──────
╰────

⚠ eslint(no-redeclare): 'a' is already defined.
╭─[no_redeclare.tsx:1:5]
1 │ var a; var {a = 0, b: globalThis = 0} = {};
Expand All @@ -139,6 +163,12 @@ source: crates/oxc_linter/src/tester.rs
· ╰── 'a' is already defined.
╰────

⚠ eslint(no-redeclare): 'globalThis' is already defined as a built-in global variable.
╭─[no_redeclare.tsx:1:23]
1 │ var a; var {a = 0, b: globalThis = 0} = {};
· ──────────
╰────

⚠ eslint(no-redeclare): 'a' is already defined.
╭─[no_redeclare.tsx:1:20]
1 │ function f() { var a; var a; }
Expand All @@ -149,12 +179,20 @@ source: crates/oxc_linter/src/tester.rs

⚠ eslint(no-redeclare): 'a' is already defined.
╭─[no_redeclare.tsx:1:12]
1 │ function f(a) { var a; }
· ┬ ┬
· │ ╰── It can not be redeclare here.
1 │ function f(a, b = 1) { var a; var b;}
· ┬ ┬
· │ ╰── It can not be redeclare here.
· ╰── 'a' is already defined.
╰────

⚠ eslint(no-redeclare): 'b' is already defined.
╭─[no_redeclare.tsx:1:15]
1 │ function f(a, b = 1) { var a; var b;}
· ┬ ┬
· │ ╰── It can not be redeclare here.
· ╰── 'b' is already defined.
╰────

⚠ eslint(no-redeclare): 'a' is already defined.
╭─[no_redeclare.tsx:1:20]
1 │ function f() { var a; if (test) { var a; } }
Expand Down