feat: add new rule no-empty-static-block (#16325)

* feat: add `no-empty-static-block`

* docs: add docs for `no-empty-static-block`

* chore: add `no-empty-static-block`

* test: add tests for multiple static blocks

* Add `further_reading`

* test: specify `ecmaVersion` at `RuleTester`

* docs: remove options section

* fix: `disallows` -> `disallow`

* fix: remove `loc` parameters

* feat: ignore comment that isn't inside block

* fix: address review

docs/src/_data/further_reading_links.json

@@ -698,5 +698,12 @@
         "logo": "https://eslint.org/apple-touch-icon.png",
         "title": "Interesting bugs caught by no-constant-binary-expression - ESLint - Pluggable JavaScript Linter",
         "description": "A pluggable and configurable linter tool for identifying and reporting on patterns in JavaScript. Maintain your code quality with ease."
+    },
+    "https://github.com/tc39/proposal-class-static-block": {
+        "domain": "github.com",
+        "url": "https://github.com/tc39/proposal-class-static-block",
+        "logo": "https://github.com/fluidicon.png",
+        "title": "GitHub - tc39/proposal-class-static-block: ECMAScript class static initialization blocks",
+        "description": "ECMAScript class static initialization blocks. Contribute to tc39/proposal-class-static-block development by creating an account on GitHub."
     }
 }

docs/src/rules/no-empty-static-block.md

@@ -0,0 +1,56 @@
+---
+title: no-empty-static-block
+layout: doc
+rule_type: suggestion
+related_rules:
+- no-empty
+- no-empty-function
+further_reading:
+- https://github.com/tc39/proposal-class-static-block
+---
+
+Empty static blocks, while not technically errors, usually occur due to refactoring that wasn't completed. They can cause confusion when reading code.
+
+## Rule Details
+
+This rule disallows empty static blocks. This rule ignores static blocks which contain a comment.
+
+Examples of **incorrect** code for this rule:
+
+::: incorrect
+
+```js
+/*eslint no-empty-static-block: "error"*/
+
+class Foo {
+    static {}
+}
+```
+
+:::
+
+Examples of **correct** code for this rule:
+
+:::correct
+
+```js
+/*eslint no-empty-static-block: "error"*/
+
+class Foo {
+    static {
+        bar();
+    }
+}
+
+class Foo {
+    static {
+        // comment
+    }
+}
+```
+
+:::
+
+## When Not To Use It
+
+This rule should not be used in environments prior to ES2022.

lib/rules/index.js

@@ -123,6 +123,7 @@ module.exports = new LazyLoadingRuleMap(Object.entries({
     "no-empty-character-class": () => require("./no-empty-character-class"),
     "no-empty-function": () => require("./no-empty-function"),
     "no-empty-pattern": () => require("./no-empty-pattern"),
+    "no-empty-static-block": () => require("./no-empty-static-block"),
     "no-eq-null": () => require("./no-eq-null"),
     "no-eval": () => require("./no-eval"),
     "no-ex-assign": () => require("./no-ex-assign"),

lib/rules/no-empty-static-block.js

@@ -0,0 +1,47 @@
+/**
+ * @fileoverview Rule to disallow empty static blocks.
+ * @author Sosuke Suzuki
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+/** @type {import('../shared/types').Rule} */
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "Disallow empty static blocks",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-empty-static-block"
+        },
+
+        schema: [],
+
+        messages: {
+            unexpected: "Unexpected empty static block."
+        }
+    },
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+
+        return {
+            StaticBlock(node) {
+                if (node.body.length === 0) {
+                    const closingBrace = sourceCode.getLastToken(node);
+
+                    if (sourceCode.getCommentsBefore(closingBrace).length === 0) {
+                        context.report({
+                            node,
+                            messageId: "unexpected"
+                        });
+                    }
+                }
+            }
+        };
+    }
+};

tests/lib/rules/no-empty-static-block.js

@@ -0,0 +1,51 @@
+/**
+ * @fileoverview Tests for no-empty-static-block rule.
+ * @author Sosuke Suzuki
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require("../../../lib/rules/no-empty-static-block"),
+    { RuleTester } = require("../../../lib/rule-tester");
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({
+    parserOptions: { ecmaVersion: 2022 }
+});
+
+ruleTester.run("no-empty-static-block", rule, {
+    valid: [
+        "class Foo { static { bar(); } }",
+        "class Foo { static { /* comments */ } }",
+        "class Foo { static {\n// comment\n} }",
+        "class Foo { static { bar(); } static { bar(); } }"
+    ],
+    invalid: [
+        {
+            code: "class Foo { static {} }",
+            errors: [{ messageId: "unexpected" }]
+        },
+        {
+            code: "class Foo { static { } }",
+            errors: [{ messageId: "unexpected" }]
+        },
+        {
+            code: "class Foo { static { \n\n } }",
+            errors: [{ messageId: "unexpected" }]
+        },
+        {
+            code: "class Foo { static { bar(); } static {} }",
+            errors: [{ messageId: "unexpected" }]
+        },
+        {
+            code: "class Foo { static // comment\n {} }",
+            errors: [{ messageId: "unexpected" }]
+        }
+    ]
+});

tools/rule-types.json

@@ -110,6 +110,7 @@
     "no-empty-character-class": "problem",
     "no-empty-function": "suggestion",
     "no-empty-pattern": "problem",
+    "no-empty-static-block": "suggestion",
     "no-eq-null": "suggestion",
     "no-eval": "suggestion",
     "no-ex-assign": "problem",