feat(linter): add import/exports-last

crates/oxc_linter/src/rules.rs

@@ -7,6 +7,7 @@
 
 /// <https://github.com/import-js/eslint-plugin-import>
 mod import {
+    pub mod exports_last;
     pub mod no_absolute_path;
     pub mod no_mutable_exports;
     // pub mod no_deprecated;
@@ -694,6 +695,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::yoda,
     import::default,
     import::export,
+    import::exports_last,
     import::first,
     import::no_absolute_path,
     import::no_mutable_exports,

crates/oxc_linter/src/rules/import/exports_last.rs

@@ -0,0 +1,176 @@
+use itertools::Itertools;
+use oxc_ast::{
+    AstKind,
+    ast::{ModuleDeclaration, Statement},
+};
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_macros::declare_oxc_lint;
+use oxc_span::{GetSpan, Span};
+
+use crate::{context::LintContext, rule::Rule};
+
+fn exports_last_diagnostic(span: Span) -> OxcDiagnostic {
+    // See <https://oxc.rs/docs/contribute/linter/adding-rules.html#diagnostics> for details
+    OxcDiagnostic::warn("Export statements should appear at the end of the file").with_label(span)
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct ExportsLast;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// This rule enforces that all exports are declared at the bottom of the file.
+    /// This rule will report any export declarations that comes before any non-export statements.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// Exports scattered throughout the file can lead to poor code readability
+    /// and increase the cost of locating the export quickly
+    ///
+    /// ### Examples
+    ///
+    /// Examples of **incorrect** code for this rule:
+    /// ```js
+    /// const bool = true
+    /// export const foo = 'bar'
+    /// const str = 'foo'
+    /// ```
+    ///
+    /// Examples of **correct** code for this rule:
+    /// ```js
+    /// const arr = ['bar']
+    /// export const bool = true
+    /// export const str = 'foo'
+    /// export function func() {
+    ///   console.log('Hello World')
+    /// }
+    /// ```
+    ExportsLast,
+    import,
+    style
+);
+
+impl Rule for ExportsLast {
+    fn run_once(&self, ctx: &LintContext<'_>) {
+        // find last non export declaration index
+        let Some(root) = ctx.nodes().root_node() else {
+            return;
+        };
+        if let AstKind::Program(program) = root.kind() {
+            let body = &program.body;
+            let find_res =
+                body.iter().rev().find_position(|statement| !is_exports_declaration(statement));
+            if let Some((index, _)) = find_res {
+                let end = body.len() - index;
+                for statement in &body[0..end] {
+                    if is_exports_declaration(statement) {
+                        ctx.diagnostic(exports_last_diagnostic(statement.span()));
+                    }
+                }
+            }
+        }
+    }
+}
+
+fn is_exports_declaration(statement: &Statement) -> bool {
+    statement.as_module_declaration().is_some_and(|declaration| {
+        matches!(
+            declaration,
+            ModuleDeclaration::ExportAllDeclaration(_)
+                | ModuleDeclaration::ExportDefaultDeclaration(_)
+                | ModuleDeclaration::ExportNamedDeclaration(_)
+        )
+    })
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        "// comment",
+        r"
+            const foo = 'bar'
+            const bar = 'baz'
+        ",
+        r"
+            const arr = ['bar']
+            export const bool = true
+        ",
+        r"
+            const foo = 'bar'
+            export {foo}
+        ",
+        r"
+            const foo = 'bar'
+            export default foo
+        ",
+        r"
+            export default foo
+            export const bar = true
+        ",
+        r"
+            const foo = 'bar'
+            export default foo
+            export const bar = true
+        ",
+        r"
+            const foo = 'bar'
+            export default function bar () {
+            const very = 'multiline'
+            }
+            export const baz = true
+        ",
+        r"
+            const foo = 'bar'
+            export default foo
+            export const so = 'many'
+            export const exports = ':)'
+            export const i = 'cant'
+            export const even = 'count'
+            export const how = 'many'
+        ",
+        "export * from './foo'",
+        r"
+            const bool = true
+            const str = 'foo'
+            export default bool
+        ",
+        r"
+            export = 4
+            let a = 4;
+        ",
+    ];
+
+    let fail = vec![
+        r"
+            const bool = true
+            export default bool
+            const str = 'foo'
+        ",
+        r"
+            export const bool = true
+            const str = 'foo'
+        ",
+        r"
+            export const foo = 'bar'
+            const bar = true
+        ",
+        r"
+            export default 'such foo many bar'
+            export const so = 'many'
+            const foo = 'bar'
+            export const exports = ':)'
+            export const i = 'cant'
+            export const even = 'count'
+            export const how = 'many'
+        ",
+        r"
+            export * from './foo'         ;
+            const bar = true
+        ",
+    ];
+
+    Tester::new(ExportsLast::NAME, ExportsLast::PLUGIN, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/import_exports_last.snap

@@ -0,0 +1,50 @@
+---
+source: crates/oxc_linter/src/tester.rs
+---
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:3:13]
+ 2 │             const bool = true
+ 3 │             export default bool
+   ·             ───────────────────
+ 4 │             const str = 'foo'
+   ╰────
+
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:2:13]
+ 1 │ 
+ 2 │             export const bool = true
+   ·             ────────────────────────
+ 3 │             const str = 'foo'
+   ╰────
+
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:2:13]
+ 1 │ 
+ 2 │             export const foo = 'bar'
+   ·             ────────────────────────
+ 3 │             const bar = true
+   ╰────
+
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:2:13]
+ 1 │ 
+ 2 │             export default 'such foo many bar'
+   ·             ──────────────────────────────────
+ 3 │             export const so = 'many'
+   ╰────
+
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:3:13]
+ 2 │             export default 'such foo many bar'
+ 3 │             export const so = 'many'
+   ·             ────────────────────────
+ 4 │             const foo = 'bar'
+   ╰────
+
+  ⚠ eslint-plugin-import(exports-last): Export statements should appear at the end of the file
+   ╭─[exports_last.tsx:2:13]
+ 1 │ 
+ 2 │             export * from './foo'         ;
+   ·             ───────────────────────────────
+ 3 │             const bar = true
+   ╰────