Add rule S1068 (no-unused-private-class-members): Unused private class members should be removed

its/ruling/src/test/expected/js/file-for-rules/javascript-S1068.json

@@ -0,0 +1,6 @@
+{
+"file-for-rules:S1068.js": [
+2,
+3
+]
+}

its/ruling/src/test/expected/js/file-for-rules/javascript-S1451.json

@@ -1,4 +1,7 @@
 {
+"file-for-rules:S1068.js": [
+0
+],
 "file-for-rules:S1534.js": [
 0
 ],

its/sources/file-for-rules/S1068.js

@@ -0,0 +1,5 @@
+class MyClass {
+  #privateField;
+  #privateMethod(){/* empty */}
+  otherMethod(){/* empty */}
+}

sonar-plugin/javascript-checks/src/main/java/org/sonar/javascript/checks/CheckList.java

@@ -294,6 +294,7 @@ public static List<Class<? extends JavaScriptCheck>> getAllChecks() {
       NoUnsafeOptionalChainingCheck.class,
       NoUnstableNestedComponentsCheck.class,
       NoUnusedClassComponentMethodsCheck.class,
+      NoUnusedPrivateClassMembersCheck.class,
       NoUselessCallCheck.class,
       NoUselessCatchCheck.class,
       NoUselessConstructorCheck.class,

sonar-plugin/javascript-checks/src/main/java/org/sonar/javascript/checks/NoUnusedPrivateClassMembersCheck.java

@@ -0,0 +1,36 @@
+/**
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2023 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package org.sonar.javascript.checks;
+
+import org.sonar.check.Rule;
+import org.sonar.plugins.javascript.api.EslintBasedCheck;
+import org.sonar.plugins.javascript.api.JavaScriptRule;
+import org.sonar.plugins.javascript.api.TypeScriptRule;
+
+@TypeScriptRule
+@JavaScriptRule
+@Rule(key = "S1068")
+public class NoUnusedPrivateClassMembersCheck implements EslintBasedCheck {
+
+  @Override
+  public String eslintKey() {
+    return "no-unused-private-class-members";
+  }
+}

sonar-plugin/javascript-checks/src/main/resources/org/sonar/l10n/javascript/rules/javascript/S1068.html

@@ -0,0 +1,25 @@
+<h2>Why is this an issue?</h2>
+<p>If a private member of the class is declared but not used in the program, it can be considered dead code and should therefore be removed. This will
+improve maintainability because developers will not wonder what the variable is used for.</p>
+<p>The private class members were introduced in ES2022 and use <code>#</code> hash symbol prefix. It is possible to declare private fields, methods,
+getters and setters as well as their static counterparts.</p>
+<pre data-diff-id="1" data-diff-type="noncompliant">
+class MyClass {
+    #privateField; // Noncompliant, #privateField is unused
+    #privateMethod(){} // Noncompliant, #privateMethod is unused
+    // ...
+}
+</pre>
+<p>To fix the code remove unused private member of the class.</p>
+<pre data-diff-id="1" data-diff-type="compliant">
+class MyClass {
+    // ...
+}
+</pre>
+<h2>Resources</h2>
+<h3>Documentation</h3>
+<ul>
+  <li> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Private_class_fields">MDN - private class members</a> </li>
+  <li> <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes">MDN - classes overview</a> </li>
+</ul>
+

sonar-plugin/javascript-checks/src/main/resources/org/sonar/l10n/javascript/rules/javascript/S1068.json

@@ -0,0 +1,21 @@
+{
+  "title": "Unused private class members should be removed",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "unused"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-1068",
+  "sqKey": "S1068",
+  "scope": "All",
+  "quickfix": "unknown",
+  "compatibleLanguages": [
+    "JAVASCRIPT",
+    "TYPESCRIPT"
+  ]
+}

sonar-plugin/javascript-checks/src/main/resources/org/sonar/l10n/javascript/rules/javascript/Sonar_way_profile.json

@@ -10,6 +10,7 @@
     "S888",
     "S905",
     "S930",
+    "S1068",
     "S1119",
     "S1121",
     "S1125",

src/linting/eslint/linter/quickfixes/rules.ts

@@ -60,6 +60,7 @@ export const quickFixRules = new Set([
   'no-lonely-if',
   'no-throw-literal',
   'no-unreachable',
+  'no-unused-private-class-members',
   'no-useless-call',
   'no-useless-constructor',
   'prefer-object-spread',

src/linting/eslint/rules/decorators/index.ts

@@ -40,6 +40,7 @@ import { decorateNoThrowLiteral } from './no-throw-literal-decorator';
 import { decorateNoUnreachable } from './no-unreachable-decorator';
 import { decorateNoUnstableNestedComponents } from './no-unstable-nested-components';
 import { decorateNoUnusedExpressions } from './no-unused-expressions-decorator';
+import { decorateNoUnusedPrivateClassMembers } from './no-unused-private-class-members-decorator';
 import { decorateNoUselessCall } from './no-useless-call-decorator';
 import { decorateNoUselessConstructor } from './no-useless-constructor-decorator';
 import { decorateObjectShorthand } from './object-shorthand-decorator';
@@ -95,6 +96,7 @@ export const decorators: Record<string, RuleDecorator> = {
   'no-unreachable': decorateNoUnreachable,
   'no-unstable-nested-components': decorateNoUnstableNestedComponents,
   'no-unused-expressions': decorateNoUnusedExpressions,
+  'no-unused-private-class-members': decorateNoUnusedPrivateClassMembers,
   'no-useless-call': decorateNoUselessCall,
   'no-useless-constructor': decorateNoUselessConstructor,
   'no-var': decorateNoVar,

src/linting/eslint/rules/decorators/no-unused-private-class-members-decorator.ts

@@ -0,0 +1,38 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2023 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+// https://sonarsource.github.io/rspec/#/rspec/S1068/javascript
+
+import { Rule } from 'eslint';
+import * as estree from 'estree';
+import { interceptReport } from './helpers';
+
+// core implementation of this rule does not provide quick fixes
+export function decorateNoUnusedPrivateClassMembers(rule: Rule.RuleModule): Rule.RuleModule {
+  rule.meta!.hasSuggestions = true;
+  return interceptReport(rule, (context, reportDescriptor) => {
+    const suggest: Rule.SuggestionReportDescriptor[] = [];
+    const node = (reportDescriptor as any).node as estree.Node;
+    suggest.push({
+      desc: 'Remove unused private class member',
+      fix: fixer => fixer.remove(node),
+    });
+    context.report({ ...reportDescriptor, suggest });
+  });
+}

tests/linting/eslint/linter/fixtures/wrapper/quickfixes/no-unused-private-class-members.js

@@ -0,0 +1,6 @@
+class MyClass {
+    #privateField;
+    #privateMethod(){/* empty */}
+    otherMethod(){/* empty */}
+  }
+

tests/linting/eslint/rules/decorators/no-unused-private-class-members-decorator.test.ts

@@ -0,0 +1,119 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2023 SonarSource SA
+ * mailto:info AT sonarsource DOT com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+import { RuleTester } from 'eslint';
+import { eslintRules } from 'linting/eslint/rules/core';
+import { decorateNoUnusedPrivateClassMembers } from 'linting/eslint/rules/decorators/no-unused-private-class-members-decorator';
+
+const rule = decorateNoUnusedPrivateClassMembers(eslintRules['no-unused-private-class-members']);
+const ruleTester = new RuleTester({
+  parserOptions: { ecmaVersion: 2022 },
+});
+
+ruleTester.run(`Unused private class members should be removed`, rule, {
+  valid: [
+    {
+      code: `
+        class MyClass{
+          #foo = 123;
+          bar(){return this.#foo;}
+        }`,
+    },
+  ],
+  invalid: [
+    {
+      code: `class MyClass{ #foo = 123; }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+    {
+      code: `class MyClass{ #foo(){} }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+    {
+      code: `class MyClass{ get #foo(){} }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+    {
+      code: `class MyClass{ set #foo(v){} }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+    {
+      code: `class MyClass{ static #foo = 123; }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+    {
+      code: `class MyClass{ static #foo(){} }`,
+      errors: [
+        {
+          suggestions: [
+            {
+              desc: 'Remove unused private class member',
+              output: `class MyClass{  }`,
+            },
+          ],
+        },
+      ],
+    },
+  ],
+});