GCI3 [TEAM LESS][2025] Implement rule GCI3: avoid getting size collection in loop

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 -   [#51](https://github.com/green-code-initiative/creedengo-javascript/pull/51) Add ESLint v9 and flat config support
+-   [#88](https://github.com/green-code-initiative/creedengo-javascript/pull/88) Add rule `@creedengo/avoid-gettint-size-collection-in-loop` (GCI3)
 
 ### Changed
 

eslint-plugin/README.md

@@ -109,23 +109,24 @@ If your project uses a legacy ESLint version, it may use as well the now depreca
 ✅ Set in the `flat/recommended` configuration.\
 ✅ Set in the `recommended` configuration.
 
-| Name                                                                                           | Description                                               | ⚠️  |
-| :--------------------------------------------------------------------------------------------- | :-------------------------------------------------------- | :-- |
-| [avoid-autoplay](docs/rules/avoid-autoplay.md)                                                 | Avoid autoplay for videos and audio content               | ✅ |
-| [avoid-brightness-override](docs/rules/avoid-brightness-override.md)                           | Should avoid to override brightness                       | ✅ |
-| [avoid-css-animations](docs/rules/avoid-css-animations.md)                                     | Avoid usage of CSS animations                             | ✅ |
-| [avoid-high-accuracy-geolocation](docs/rules/avoid-high-accuracy-geolocation.md)               | Avoid using high accuracy geolocation in web applications | ✅ |
-| [avoid-keep-awake](docs/rules/avoid-keep-awake.md)                                             | Avoid screen keep awake                                   | ✅ |
-| [limit-db-query-results](docs/rules/limit-db-query-results.md)                                 | Should limit the number of returns for a SQL query        | ✅ |
-| [no-empty-image-src-attribute](docs/rules/no-empty-image-src-attribute.md)                     | Disallow usage of image with empty source attribute       | ✅ |
-| [no-import-all-from-library](docs/rules/no-import-all-from-library.md)                         | Should not import all from library                        | ✅ |
-| [no-multiple-access-dom-element](docs/rules/no-multiple-access-dom-element.md)                 | Disallow multiple access of same DOM element              | ✅ |
-| [no-multiple-style-changes](docs/rules/no-multiple-style-changes.md)                           | Disallow multiple style changes at once                   | ✅ |
-| [no-torch](docs/rules/no-torch.md)                                                             | Should not programmatically enable torch mode             | ✅ |
-| [prefer-collections-with-pagination](docs/rules/prefer-collections-with-pagination.md)         | Prefer API collections with pagination                    | ✅ |
-| [prefer-lighter-formats-for-image-files](docs/rules/prefer-lighter-formats-for-image-files.md) | Prefer lighter formats for image files                    | ✅ |
-| [prefer-shorthand-css-notations](docs/rules/prefer-shorthand-css-notations.md)                 | Encourage usage of shorthand CSS notations                | ✅ |
-| [provide-print-css](docs/rules/provide-print-css.md)                                           | Enforce providing a print stylesheet                      | ✅ |
+| Name                                                                                           | Description                                                                                                               | ⚠️  |
+| :--------------------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------------------------------------------ | :-- |
+| [avoid-autoplay](docs/rules/avoid-autoplay.md)                                                 | Avoid autoplay for videos and audio content                                                                               | ✅ |
+| [avoid-brightness-override](docs/rules/avoid-brightness-override.md)                           | Should avoid to override brightness                                                                                       | ✅ |
+| [avoid-css-animations](docs/rules/avoid-css-animations.md)                                     | Avoid usage of CSS animations                                                                                             | ✅ |
+| [avoid-getting-size-collection-in-loop](docs/rules/avoid-getting-size-collection-in-loop.md)   | Avoid getting the size/length of the collection in loops and callbacks. Assign it to a variable before the loop/callback. | ✅ |
+| [avoid-high-accuracy-geolocation](docs/rules/avoid-high-accuracy-geolocation.md)               | Avoid using high accuracy geolocation in web applications                                                                 | ✅ |
+| [avoid-keep-awake](docs/rules/avoid-keep-awake.md)                                             | Avoid screen keep awake                                                                                                   | ✅ |
+| [limit-db-query-results](docs/rules/limit-db-query-results.md)                                 | Should limit the number of returns for a SQL query                                                                        | ✅ |
+| [no-empty-image-src-attribute](docs/rules/no-empty-image-src-attribute.md)                     | Disallow usage of image with empty source attribute                                                                       | ✅ |
+| [no-import-all-from-library](docs/rules/no-import-all-from-library.md)                         | Should not import all from library                                                                                        | ✅ |
+| [no-multiple-access-dom-element](docs/rules/no-multiple-access-dom-element.md)                 | Disallow multiple access of same DOM element                                                                              | ✅ |
+| [no-multiple-style-changes](docs/rules/no-multiple-style-changes.md)                           | Disallow multiple style changes at once                                                                                   | ✅ |
+| [no-torch](docs/rules/no-torch.md)                                                             | Should not programmatically enable torch mode                                                                             | ✅ |
+| [prefer-collections-with-pagination](docs/rules/prefer-collections-with-pagination.md)         | Prefer API collections with pagination                                                                                    | ✅ |
+| [prefer-lighter-formats-for-image-files](docs/rules/prefer-lighter-formats-for-image-files.md) | Prefer lighter formats for image files                                                                                    | ✅ |
+| [prefer-shorthand-css-notations](docs/rules/prefer-shorthand-css-notations.md)                 | Encourage usage of shorthand CSS notations                                                                                | ✅ |
+| [provide-print-css](docs/rules/provide-print-css.md)                                           | Enforce providing a print stylesheet                                                                                      | ✅ |
 
 <!-- end auto-generated rules list -->
 

eslint-plugin/docs/rules/avoid-getting-size-collection-in-loop.md

@@ -0,0 +1,26 @@
+# Avoid getting the size/length of the collection in loops and callbacks. Assign it to a variable before the loop/callback (`@creedengo/avoid-getting-size-collection-in-loop`)
+
+⚠️ This rule _warns_ in the following configs: ✅ `flat/recommended`, ✅ `recommended`.
+
+<!-- end auto-generated rule header -->
+
+## Why is this an issue ?
+
+Accessing the size or length of a collection (such as arrays, maps, or sets) inside a loop can lead to unnecessary performance overhead, especially if the collection size is recalculated on each iteration. This rule warns when the size of a collection is accessed within a loop condition or body, encouraging developers to cache the size before the loop.
+
+### Examples of **incorrect** code
+
+```javascript
+for (let i = 0; i < array.length; i++) {
+  doSomething(array[i]);
+}
+```
+
+### Examples of **correct** code
+
+```javascript
+const len = array.length;
+for (let i = 0; i < len; i++) {
+  doSomething(array[i]);
+}
+```

eslint-plugin/lib/rules/avoid-getting-size-collection-in-loop.js

@@ -0,0 +1,135 @@
+/*
+ * creedengo JavaScript plugin - Provides rules to reduce the environmental footprint of your JavaScript programs
+ * Copyright © 2023 Green Code Initiative (https://green-code-initiative.org)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+/** @type {import("eslint").Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: "suggestion",
+    docs: {
+      description:
+        "Avoid getting the size/length of the collection in loops and callbacks. Assign it to a variable before the loop/callback.",
+      category: "eco-design",
+      recommended: "warn",
+    },
+    messages: {
+      avoidSizeInLoop:
+        "Avoid getting the size/length of the collection in the loop or callback. Assign it to a variable before the loop/callback.",
+    },
+    schema: [],
+  },
+  create: function (context) {
+    const SIZE_PROPERTIES = ["length", "size"]; // We only include static analysis on size and length properties at the moment
+    const CALLBACK_METHODS = [
+      "filter",
+      "find",
+      "findIndex",
+      "findLast",
+      "findLastIndex",
+      "every",
+      "flatMap",
+      "forEach",
+      "map",
+      "reduce",
+      "reduceRight",
+      "some",
+    ];
+
+    /**
+     * Checks if a node is a .length or .size property access (dot or bracket notation).
+     * If you want to only match dot notation, keep !node.computed.
+     */
+    function isSizeOrLengthMember(node) {
+      return (
+        node.type === "MemberExpression" &&
+        SIZE_PROPERTIES.includes(node.property.name)
+      );
+    }
+
+    /**
+     * Recursively walk the AST node and report if .length or .size is accessed.
+     */
+    function checkNodeRecursively(node) {
+      if (!node) return;
+
+      if (isSizeOrLengthMember(node)) {
+        context.report({ node, messageId: "avoidSizeInLoop" });
+        return;
+      }
+
+      for (const key in node) {
+        // Prevents infinite recursion
+        if (key === "parent") continue;
+        if (!Object.prototype.hasOwnProperty.call(node, key)) continue;
+
+        // Recursively check on each child nodes
+        const child = node[key];
+        if (Array.isArray(child)) {
+          child.forEach(checkNodeRecursively);
+        } else if (child && typeof child.type === "string") {
+          checkNodeRecursively(child);
+        }
+      }
+    }
+
+    /**
+     * Checks the callback function body of array methods like map, forEach, etc.
+     */
+    function checkCallbackArg(node) {
+      if (
+        node.arguments &&
+        node.arguments.length > 0 &&
+        (node.arguments[0].type === "FunctionExpression" ||
+          node.arguments[0].type === "ArrowFunctionExpression")
+      ) {
+        checkNodeRecursively(node.arguments[0].body);
+      }
+    }
+
+    return {
+      ForStatement(node) {
+        checkNodeRecursively(node.test);
+        checkNodeRecursively(node.body);
+      },
+      WhileStatement(node) {
+        checkNodeRecursively(node.test);
+        checkNodeRecursively(node.body);
+      },
+      DoWhileStatement(node) {
+        checkNodeRecursively(node.test);
+        checkNodeRecursively(node.body);
+      },
+      ForInStatement(node) {
+        checkNodeRecursively(node.body);
+      },
+      ForOfStatement(node) {
+        checkNodeRecursively(node.body);
+      },
+      CallExpression(node) {
+        if (
+          node.callee &&
+          node.callee.type === "MemberExpression" &&
+          CALLBACK_METHODS.includes(node.callee.property.name)
+        ) {
+          checkCallbackArg(node);
+        }
+      },
+    };
+  },
+};