feat: add ignoreClassWithStaticInitBlock option to no-unused-vars (#18170)

Tanujkanti4441 · web-flow · commit 1c173dc1f3d3 · 2024-03-07T13:35:22.000+01:00
* feat: add option to ignore SIB-classes

* add docs and tests

* add test

* update docs
diff --git a/docs/src/rules/no-unused-vars.md b/docs/src/rules/no-unused-vars.md
@@ -410,6 +410,51 @@ var bar;
 
 :::
 
+### ignoreClassWithStaticInitBlock
+
+The `ignoreClassWithStaticInitBlock` option is a boolean (default: `false`). Static initialization blocks allow you to initialize static variables and execute code during the evaluation of a class definition, meaning the static block code is executed without creating a new instance of the class. When set to `true`, this option ignores classes containing static initialization blocks.
+
+Examples of **incorrect** code for the `{ "ignoreClassWithStaticInitBlock": true }` option
+
+::: incorrect
+
+```js
+/*eslint no-unused-vars: ["error", { "ignoreClassWithStaticInitBlock": true }]*/
+
+class Foo {
+    static myProperty = "some string";
+    static mymethod() {
+        return "some string";
+    }
+}
+
+class Bar {
+    static {
+        let baz; // unused variable
+    }
+}
+```
+
+:::
+
+Examples of **correct** code for the `{ "ignoreClassWithStaticInitBlock": true }` option
+
+::: correct
+
+```js
+/*eslint no-unused-vars: ["error", { "ignoreClassWithStaticInitBlock": true }]*/
+
+class Foo {
+    static {
+        let bar = "some string";
+
+        console.log(bar);
+    }
+}
+```
+
+:::
+
 ## When Not To Use It
 
 If you don't want to be notified about unused variables or function arguments, you can safely turn this rule off.
diff --git a/lib/rules/no-unused-vars.js b/lib/rules/no-unused-vars.js
@@ -70,6 +70,9 @@ module.exports = {
                             },
                             destructuredArrayIgnorePattern: {
                                 type: "string"
+                            },
+                            ignoreClassWithStaticInitBlock: {
+                                type: "boolean"
                             }
                         },
                         additionalProperties: false
@@ -92,7 +95,8 @@ module.exports = {
             vars: "all",
             args: "after-used",
             ignoreRestSiblings: false,
-            caughtErrors: "all"
+            caughtErrors: "all",
+            ignoreClassWithStaticInitBlock: false
         };
 
         const firstOption = context.options[0];
@@ -105,6 +109,7 @@ module.exports = {
                 config.args = firstOption.args || config.args;
                 config.ignoreRestSiblings = firstOption.ignoreRestSiblings || config.ignoreRestSiblings;
                 config.caughtErrors = firstOption.caughtErrors || config.caughtErrors;
+                config.ignoreClassWithStaticInitBlock = firstOption.ignoreClassWithStaticInitBlock || config.ignoreClassWithStaticInitBlock;
 
                 if (firstOption.varsIgnorePattern) {
                     config.varsIgnorePattern = new RegExp(firstOption.varsIgnorePattern, "u");
@@ -613,6 +618,14 @@ module.exports = {
                             continue;
                         }
 
+                        if (type === "ClassName") {
+                            const hasStaticBlock = def.node.body.body.some(node => node.type === "StaticBlock");
+
+                            if (config.ignoreClassWithStaticInitBlock && hasStaticBlock) {
+                                continue;
+                            }
+                        }
+
                         // skip catch variables
                         if (type === "CatchClause") {
                             if (config.caughtErrors === "none") {
diff --git a/tests/lib/rules/no-unused-vars.js b/tests/lib/rules/no-unused-vars.js
@@ -445,6 +445,23 @@ ruleTester.run("no-unused-vars", rule, {
         {
             code: "var a; a ??= 1;",
             languageOptions: { ecmaVersion: 2021 }
+        },
+
+        // ignore class with static initialization block https://github.com/eslint/eslint/issues/17772
+        {
+            code: "class Foo { static {} }",
+            options: [{ ignoreClassWithStaticInitBlock: true }],
+            languageOptions: { ecmaVersion: 2022 }
+        },
+        {
+            code: "class Foo { static {} }",
+            options: [{ ignoreClassWithStaticInitBlock: true, varsIgnorePattern: "^_" }],
+            languageOptions: { ecmaVersion: 2022 }
+        },
+        {
+            code: "class Foo { static {} }",
+            options: [{ ignoreClassWithStaticInitBlock: false, varsIgnorePattern: "^Foo" }],
+            languageOptions: { ecmaVersion: 2022 }
         }
     ],
     invalid: [
@@ -1557,6 +1574,43 @@ function foo1() {
 c = foo1`,
             languageOptions: { ecmaVersion: 2020 },
             errors: [{ ...assignedError("c"), line: 10, column: 1 }]
+        },
+
+        // ignore class with static initialization block https://github.com/eslint/eslint/issues/17772
+        {
+            code: "class Foo { static {} }",
+            options: [{ ignoreClassWithStaticInitBlock: false }],
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("Foo"), line: 1, column: 7 }]
+        },
+        {
+            code: "class Foo { static {} }",
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("Foo"), line: 1, column: 7 }]
+        },
+        {
+            code: "class Foo { static { var bar; } }",
+            options: [{ ignoreClassWithStaticInitBlock: true }],
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("bar"), line: 1, column: 26 }]
+        },
+        {
+            code: "class Foo {}",
+            options: [{ ignoreClassWithStaticInitBlock: true }],
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("Foo"), line: 1, column: 7 }]
+        },
+        {
+            code: "class Foo { static bar; }",
+            options: [{ ignoreClassWithStaticInitBlock: true }],
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("Foo"), line: 1, column: 7 }]
+        },
+        {
+            code: "class Foo { static bar() {} }",
+            options: [{ ignoreClassWithStaticInitBlock: true }],
+            languageOptions: { ecmaVersion: 2022 },
+            errors: [{ ...definedError("Foo"), line: 1, column: 7 }]
         }
     ]
 });
