feat(linter): implement @typescript-eslint/no-empty-interface

crates/oxc_linter/src/rules.rs

@@ -54,6 +54,7 @@ oxc_macros::declare_all_lint_rules! {
     eslint::use_isnan,
     eslint::valid_typeof,
     typescript::isolated_declaration,
+    typescript::no_empty_interface,
     typescript::no_extra_non_null_assertion,
     typescript::no_non_null_asserted_optional_chain
 }

crates/oxc_linter/src/rules/typescript/no_empty_interface.rs

@@ -0,0 +1,91 @@
+use oxc_ast::AstKind;
+use oxc_diagnostics::{
+    miette::{self, Diagnostic},
+    thiserror::Error,
+};
+use oxc_macros::declare_oxc_lint;
+use oxc_span::Span;
+
+use crate::{context::LintContext, rule::Rule, AstNode};
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("typescript-eslint(no-empty-interface): an empty interface is equivalent to `{{}}`")]
+#[diagnostic(severity(warning))]
+struct NoEmptyInterfaceDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Error, Diagnostic)]
+#[error(
+    "typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype"
+)]
+#[diagnostic(severity(warning))]
+struct NoEmptyInterfaceExtendDiagnostic(#[label] pub Span);
+
+#[derive(Debug, Default, Clone)]
+pub struct NoEmptyInterface;
+
+declare_oxc_lint!(
+    /// ### What it does
+    ///
+    /// Disallow the declaration of empty interfaces.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// An empty interface in TypeScript does very little: any non-nullable value is assignable to {}.
+    /// Using an empty interface is often a sign of programmer error, such as misunderstanding the concept of {} or forgetting to fill in fields.
+    /// This rule aims to ensure that only meaningful interfaces are declared in the code.
+    ///
+    /// ### Example
+    /// ```javascript
+    /// interface Foo {}
+    /// interface Bar extends Foo {}
+    /// ```
+    NoEmptyInterface,
+    correctness
+);
+
+impl Rule for NoEmptyInterface {
+    fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
+        if let AstKind::TSInterfaceDeclaration(interface) = node.kind() {
+            if interface.body.body.is_empty() {
+                match &interface.extends {
+                    None => {
+                        ctx.diagnostic(NoEmptyInterfaceDiagnostic(interface.span));
+                    }
+                    Some(extends) if extends.len() == 1 => {
+                        ctx.diagnostic(NoEmptyInterfaceExtendDiagnostic(interface.span));
+                    }
+                    _ => {}
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn test() {
+    use crate::tester::Tester;
+
+    let pass = vec![
+        "interface Foo { name: string; }",
+        "interface Foo { name: string; }
+        interface Bar { age: number; }
+        // valid because extending multiple interfaces can be used instead of a union type
+        interface Baz extends Foo, Bar {}",
+    ];
+
+    let fail = vec![
+        "interface Foo {}",
+        "interface Foo { props: string; } interface Bar extends Foo {} class Baz {}",
+        "interface Foo { props: string; } interface Bar extends Foo {} class Bar {}",
+        "interface Foo { props: string; } interface Bar extends Foo {} const bar = class Bar {};",
+        "interface Foo { name: string; } interface Bar extends Foo {}",
+        "interface Foo extends Array<number> {}",
+        "interface Foo extends Array<number | {}> {}",
+        "interface Bar { bar: string; } interface Foo extends Array<Bar> {}",
+        "type R = Record<string, unknown>; interface Foo extends R {}",
+        "interface Foo<T> extends Bar<T> {}",
+        "declare module FooBar { type Baz = typeof baz; export interface Bar extends Baz {} }",
+    ];
+
+    Tester::new_without_config(NoEmptyInterface::NAME, pass, fail).test_and_snapshot();
+}

crates/oxc_linter/src/snapshots/no_empty_interface.snap

@@ -0,0 +1,71 @@
+---
+source: crates/oxc_linter/src/tester.rs
+expression: no_empty_interface
+---
+  ⚠ typescript-eslint(no-empty-interface): an empty interface is equivalent to `{}`
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo {}
+   · ────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo { props: string; } interface Bar extends Foo {} class Baz {}
+   ·                                  ────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo { props: string; } interface Bar extends Foo {} class Bar {}
+   ·                                  ────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo { props: string; } interface Bar extends Foo {} const bar = class Bar {};
+   ·                                  ────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo { name: string; } interface Bar extends Foo {}
+   ·                                 ────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo extends Array<number> {}
+   · ──────────────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo extends Array<number | {}> {}
+   · ───────────────────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Bar { bar: string; } interface Foo extends Array<Bar> {}
+   ·                                ───────────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ type R = Record<string, unknown>; interface Foo extends R {}
+   ·                                   ──────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ interface Foo<T> extends Bar<T> {}
+   · ──────────────────────────────────
+   ╰────
+
+  ⚠ typescript-eslint(no-empty-interface): an interface declaring no members is equivalent to its supertype
+   ╭─[no_empty_interface.tsx:1:1]
+ 1 │ declare module FooBar { type Baz = typeof baz; export interface Bar extends Baz {} }
+   ·                                                       ────────────────────────────
+   ╰────
+
+