feat(linter): add import/unambiguous rule (#7187)

crates/oxc_linter/src/rules.rs

@@ -24,6 +24,7 @@ mod import {
     pub mod no_named_as_default_member;
     pub mod no_self_import;
     pub mod no_webpack_loader_syntax;
+    pub mod unambiguous;
 }
 
 mod eslint {
@@ -635,6 +636,7 @@ oxc_macros::declare_all_lint_rules! {
     import::no_named_as_default_member,
     import::no_self_import,
     import::no_webpack_loader_syntax,
+    import::unambiguous,
     jest::consistent_test_it,
     jest::expect_expect,
     jest::max_expects,

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

@@ -0,0 +1,82 @@
+use oxc_diagnostics::OxcDiagnostic;
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule};
+
+fn unambiguous_diagnostic(span: Span) -> OxcDiagnostic {
+    OxcDiagnostic::warn("This module could be mistakenly parsed as script instead of module")
+        .with_help("Add at least one import or export statement to unambiguously mark this file as a module")
+        .with_label(span)
+}
+
+#[derive(Debug, Default, Clone)]
+pub struct Unambiguous;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Warn if a `module` could be mistakenly parsed as a `script` and not pure ESM module
+    ///
+    /// ### Why is this bad?
+    ///
+    /// For ESM-only environments helps to determine files that not pure ESM modules
+    ///
+    /// ### Examples
+    ///
+    /// Examples of **incorrect** code for this rule:
+    /// ```js
+    /// function x() {}
+    ///
+    /// (function x() { return 42 })()
+    /// ```
+    ///
+    /// Examples of **correct** code for this rule:
+    /// ```js
+    /// import 'foo'
+    /// function x() { return 42 }
+    ///
+    /// export function x() { return 42 }
+    ///
+    /// (function x() { return 42 })()
+    /// export {} // simple way to mark side-effects-only file as 'module' without any imports/exports
+    /// ```
+    Unambiguous,
+    restriction
+);
+
+/// <https://github.com/import-js/eslint-plugin-import/blob/main/docs/rules/unambiguous.md>
+impl Rule for Unambiguous {
+    fn run_once(&self, ctx: &LintContext<'_>) {
+        if ctx.semantic().module_record().not_esm {
+            ctx.diagnostic(unambiguous_diagnostic(Span::default()));
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        // looks like in original rule that should pass for ecmaVersion before 2015
+        // r"function x() {}",
+        // r#""use strict"; function y() {}"#,
+        r#"import y from "z"; function x() {}"#,
+        r#"import * as y from "z"; function x() {}"#,
+        r#"import { y } from "z"; function x() {}"#,
+        r#"import z, { y } from "z"; function x() {}"#,
+        "function x() {}; export {}",
+        "function x() {}; export { x }",
+        r#"function x() {}; export { y } from "z""#,
+        r#"function x() {}; export * as y from "z""#,
+        "export function x() {}",
+    ];
+
+    let fail = vec![r"function x() {}", r"(function x() { return 42 })()"];
+
+    Tester::new(Unambiguous::NAME, pass, fail)
+        .change_rule_path("index.ts")
+        .with_import_plugin(true)
+        .test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/unambiguous.snap

@@ -0,0 +1,16 @@
+---
+source: crates/oxc_linter/src/tester.rs
+---
+  ⚠ eslint-plugin-import(unambiguous): This module could be mistakenly parsed as script instead of module
+   ╭─[index.ts:1:1]
+ 1 │ function x() {}
+   · ▲
+   ╰────
+  help: Add at least one import or export statement to unambiguously mark this file as a module
+
+  ⚠ eslint-plugin-import(unambiguous): This module could be mistakenly parsed as script instead of module
+   ╭─[index.ts:1:1]
+ 1 │ (function x() { return 42 })()
+   · ▲
+   ╰────
+  help: Add at least one import or export statement to unambiguously mark this file as a module