Fix: Add no-magic-numbers 'ignoreDefaultValues' option

eslint · Nov 27, 2019 · 40a92dc · 40a92dc
1 parent ea16de4
commit 40a92dc
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Showing 3 changed files with 53 additions and 1 deletion.
diff --git a/docs/rules/no-magic-numbers.md b/docs/rules/no-magic-numbers.md
@@ -78,6 +78,18 @@ var data = ['foo', 'bar', 'baz'];
 var dataLast = data[2];
 ```
 
+### ignoreDefaultValues
+
+A boolean to specify if numbers used in default value assignmength are considered okay. `false` by default.
+
+Examples of **correct** code for the `{ "ignoreDefaultValues": true }` option:
+
+```js
+/*eslint no-magic-numbers: ["error", { "ignoreDefaultValues": true }]*/
+
+const { tax = 0.25 } = accountancy;
+```
+
 ### enforceConst
 
 A boolean to specify if we should check for the const keyword in variable declaration of numbers. `false` by default.

diff --git a/lib/rules/no-magic-numbers.js b/lib/rules/no-magic-numbers.js
@@ -41,6 +41,10 @@ module.exports = {
                 ignoreArrayIndexes: {
                     type: "boolean",
                     default: false
+                },
+                ignoreDefaultValues: {
+                    type: "boolean",
+                    default: false
                 }
             },
             additionalProperties: false
@@ -57,7 +61,8 @@ module.exports = {
             detectObjects = !!config.detectObjects,
             enforceConst = !!config.enforceConst,
             ignore = config.ignore || [],
-            ignoreArrayIndexes = !!config.ignoreArrayIndexes;
+            ignoreArrayIndexes = !!config.ignoreArrayIndexes,
+            ignoreDefaultValues = !!config.ignoreDefaultValues;
 
         /**
          * Returns whether the node is number literal
@@ -109,6 +114,16 @@ module.exports = {
             return parent.type === "MemberExpression" && ignoreArrayIndexes;
         }
 
+        /**
+         * Returns whether the number should be ignore when used as a default
+         * value assignment.
+         * @param {ASTNode} parent the non-"UnaryExpression" parent.
+         * @returns {boolean} true if the number should be ignored
+         */
+        function shouldIgnoreDefaultValues(parent) {
+            return parent.type === "AssignmentPattern" && ignoreDefaultValues;
+        }
+
         return {
             Literal(node) {
                 const okTypes = detectObjects ? [] : ["ObjectExpression", "Property", "AssignmentExpression"];
@@ -138,6 +153,7 @@ module.exports = {
                 if (shouldIgnoreNumber(value) ||
                     shouldIgnoreParseInt(parent, fullNumberNode) ||
                     shouldIgnoreArrayIndexes(parent) ||
+                    shouldIgnoreDefaultValues(parent) ||
                     shouldIgnoreJSXNumbers(parent)) {
                     return;
                 }

diff --git a/tests/lib/rules/no-magic-numbers.js b/tests/lib/rules/no-magic-numbers.js
@@ -75,6 +75,20 @@ ruleTester.run("no-magic-numbers", rule, {
                     jsx: true
                 }
             }
+        },
+        {
+            code: "const { param = 123 } = sourceObject;",
+            options: [{
+                ignoreDefaultValues: true
+            }],
+            env: { es6: true }
+        },
+        {
+            code: "const func = ({ param = 123 }) => {}",
+            options: [{
+                ignoreDefaultValues: true
+            }],
+            env: { es6: true }
         }
     ],
     invalid: [
@@ -227,6 +241,16 @@ ruleTester.run("no-magic-numbers", rule, {
                 { messageId: "noMagic", data: { raw: "10" }, line: 1 },
                 { messageId: "noMagic", data: { raw: "4" }, line: 1 }
             ]
+        },
+        {
+            code: "const { param = 123 } = sourceObject;",
+            options: [{
+                ignoreDefaultValues: false
+            }],
+            env: { es6: true },
+            errors: [
+                { messageId: "noMagic", data: { raw: "123" }, line: 1 }
+            ]
         }
     ]
 });