Create rule S6959: "Array.reduce()" calls should include an initial v…

…alue

its/ruling/src/test/expected/jsts/ant-design/typescript-S6959.json

@@ -0,0 +1,5 @@
+{
+"ant-design:components/anchor/Anchor.tsx": [
+189
+]
+}

its/ruling/src/test/expected/jsts/desktop/typescript-S6959.json

@@ -0,0 +1,11 @@
+{
+"desktop:app/src/lib/parse-carriage-return.ts": [
+30
+],
+"desktop:app/src/main-process/menu/build-default-menu.ts": [
+644
+],
+"desktop:app/src/ui/donut.tsx": [
+60
+]
+}

packages/jsts/src/rules/S6959/cb.fixture.ts

@@ -0,0 +1,13 @@
+function noncompliant(xs: number[]) {
+    return xs.reduce((acc, x) => acc + x); // Noncompliant {{Add an initial value to this "reduce()" call.}}
+}
+
+function compliant(xs: number[]) {
+    return xs.reduce((acc, x) => acc + x, 0); // Compliant
+}
+
+function coverage(x: any) {
+    x.m();
+    x.reduce();
+    x.reduce(42);
+}

packages/jsts/src/rules/S6959/cb.test.ts

@@ -0,0 +1,28 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 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 { check } from '../tools';
+import { rule } from './';
+import path from 'path';
+
+const sonarId = path.basename(__dirname);
+
+describe('Rule S6959', () => {
+  check(sonarId, rule, __dirname);
+});

packages/jsts/src/rules/S6959/index.ts

@@ -0,0 +1,20 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 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.
+ */
+export { rule } from './rule';

packages/jsts/src/rules/S6959/rule.ts

@@ -0,0 +1,48 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 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/S6959/javascript
+
+import { Rule } from 'eslint';
+import { isArray, isCallingMethod, isRequiredParserServices } from '../helpers';
+
+export const rule: Rule.RuleModule = {
+  meta: {
+    messages: {
+      message: 'Add an initial value to this "reduce()" call.',
+    },
+  },
+  create(context: Rule.RuleContext) {
+    const services = context.parserServices;
+    if (!isRequiredParserServices(services)) {
+      return {};
+    }
+
+    return {
+      CallExpression(node) {
+        if (isCallingMethod(node, 1, 'reduce') && isArray(node.callee.object, services)) {
+          context.report({
+            node: node.callee.property,
+            messageId: 'message',
+          });
+        }
+      },
+    };
+  },
+};

packages/jsts/src/rules/S6959/unit.test.ts

@@ -0,0 +1,31 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 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 { rule } from './';
+
+const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2018 } });
+ruleTester.run('"Array.reduce()" calls should include an initial value', rule, {
+  valid: [
+    {
+      code: 'xs.reduce((acc, x) => acc + x);',
+    },
+  ],
+  invalid: [],
+});

packages/jsts/src/rules/index.ts

@@ -244,6 +244,7 @@ import { rule as S4507 } from './S4507'; // production-debug
 import { rule as S2245 } from './S2245'; // pseudo-random
 import { rule as S1444 } from './S1444'; // public-static-readonly
 import { rule as S5443 } from './S5443'; // publicly-writable-directories
+import { rule as S6959 } from './S6959'; // reduce-initial-value
 import { rule as S6564 } from './S6564'; // redundant-type-aliases
 import { rule as S5843 } from './S5843'; // regex-complexity
 import { rule as S4784 } from './S4784'; // regular-expr
@@ -534,6 +535,7 @@ rules['production-debug'] = S4507;
 rules['pseudo-random'] = S2245;
 rules['public-static-readonly'] = S1444;
 rules['publicly-writable-directories'] = S5443;
+rules['reduce-initial-value'] = S6959;
 rules['redundant-type-aliases'] = S6564;
 rules['regex-complexity'] = S5843;
 rules['regular-expr'] = S4784;

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

@@ -394,6 +394,7 @@ public static List<Class<? extends JavaScriptCheck>> getAllChecks() {
       PubliclyWritableDirectoriesCheck.class,
       ReassignedParameterCheck.class,
       RedeclaredSymbolCheck.class,
+      ReduceInitialValueCheck.class,
       RedundantAssignmentCheck.class,
       RedundantTypeAliasesCheck.class,
       ReferenceErrorCheck.class,

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

@@ -0,0 +1,36 @@
+/*
+ * SonarQube JavaScript Plugin
+ * Copyright (C) 2011-2024 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;
+
+@JavaScriptRule
+@TypeScriptRule
+@Rule(key = "S6959")
+public class ReduceInitialValueCheck implements EslintBasedCheck {
+
+  @Override
+  public String eslintKey() {
+    return "reduce-initial-value";
+  }
+}

sonar-plugin/javascript-checks/src/main/resources/org/sonar/l10n/javascript/rules/javascript/S6959.html

@@ -0,0 +1,32 @@
+<h2>Why is this an issue?</h2>
+<p>The <code>Array.prototype.reduce()</code> method in JavaScript is used to apply a function against an accumulator and each element in the array
+(from left to right) to reduce it to a single output value. It is a convenient method that can simplify logic in your code.</p>
+<p>However, it’s important to always provide an initial value as the second argument to <code>reduce()</code>. The initial value is used as the first
+argument to the first call of the callback function. If no initial value is supplied, JavaScript will use the first element of the array as the
+initial accumulator value and start iterating at the second element.</p>
+<p>This can lead to runtime errors if the array is empty, as <code>reduce()</code> will throw a TypeError.</p>
+<pre data-diff-id="1" data-diff-type="noncompliant">
+function sum(xs) {
+  return xs.reduce((acc, current) =&gt; acc + current); // Noncompliant
+}
+console.log(sum([1, 2, 3, 4, 5])); // Prints 15
+console.log(sum([])); // TypeError: Reduce of empty array with no initial value
+</pre>
+<p>To fix this, always provide an initial value as the second argument to <code>reduce()</code>.</p>
+<pre data-diff-id="1" data-diff-type="compliant">
+function sum(xs) {
+  return xs.reduce((acc, current) =&gt; acc + current, 0);
+}
+console.log(sum([1, 2, 3, 4, 5])); // Prints 15
+console.log(sum([])); // Prints 0
+</pre>
+<h2>Resources</h2>
+<h3>Documentation</h3>
+<ul>
+  <li> MDN web docs - <a
+  href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce">Array.prototype.reduce()</a> </li>
+  <li> MDN web docs - <a
+  href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Reduce_of_empty_array_with_no_initial_value">TypeError: Reduce of
+  empty array with no initial value</a> </li>
+</ul>
+

sonar-plugin/javascript-checks/src/main/resources/org/sonar/l10n/javascript/rules/javascript/S6959.json

@@ -0,0 +1,27 @@
+{
+  "title": "\"Array.reduce()\" calls should include an initial value",
+  "type": "BUG",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant\/Issue",
+    "constantCost": "5min"
+  },
+  "tags": [
+    "type-dependent"
+  ],
+  "defaultSeverity": "Major",
+  "ruleSpecification": "RSPEC-6959",
+  "sqKey": "S6959",
+  "scope": "All",
+  "quickfix": "targeted",
+  "code": {
+    "impacts": {
+      "RELIABILITY": "MEDIUM"
+    },
+    "attribute": "CONVENTIONAL"
+  },
+  "compatibleLanguages": [
+    "JAVASCRIPT",
+    "TYPESCRIPT"
+  ]
+}

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

@@ -327,6 +327,7 @@
     "S6854",
     "S6855",
     "S6859",
-    "S6861"
+    "S6861",
+    "S6959"
   ]
 }