Update: add fixer for prefer-numeric-literals (#7205)

not-an-aardvark · nzakas · commit c05a19c0f279 · 2016-09-30T11:14:50.000-07:00
diff --git a/docs/rules/prefer-numeric-literals.md b/docs/rules/prefer-numeric-literals.md
@@ -1,5 +1,7 @@
 # disallow `parseInt()` in favor of binary, octal, and hexadecimal literals (prefer-numeric-literals)
 
+(fixable) The `--fix` option on the [command line](../user-guide/command-line-interface#fix) automatically fixes problems reported by this rule.
+
 The `parseInt()` function can be used to turn binary, octal, and hexadecimal strings into integers. As binary, octal, and hexadecimal literals are supported in ES6, this rule encourages use of those numeric literals instead of `parseInt()`.
 
 ```js
diff --git a/lib/rules/prefer-numeric-literals.js b/lib/rules/prefer-numeric-literals.js
@@ -17,7 +17,9 @@ module.exports = {
             recommended: false
         },
 
-        schema: []
+        schema: [],
+
+        fixable: "code"
     },
 
     create(context) {
@@ -27,6 +29,12 @@ module.exports = {
             16: "hexadecimal"
         };
 
+        const prefixMap = {
+            2: "0b",
+            8: "0o",
+            16: "0x"
+        };
+
         //--------------------------------------------------------------------------
         // Public
         //--------------------------------------------------------------------------
@@ -53,6 +61,17 @@ module.exports = {
                         message: "Use {{radixName}} literals instead of parseInt().",
                         data: {
                             radixName
+                        },
+                        fix(fixer) {
+                            const newPrefix = prefixMap[node.arguments[1].value];
+
+                            if (+(newPrefix + node.arguments[0].value) !== parseInt(node.arguments[0].value, node.arguments[1].value)) {
+
+                                // If the newly-produced literal would be invalid, (e.g. 0b1234),
+                                // or it would yield an incorrect parseInt result for some other reason, don't make a fix.
+                                return null;
+                            }
+                            return fixer.replaceText(node, prefixMap[node.arguments[1].value] + node.arguments[0].value);
                         }
                     });
                 }
diff --git a/tests/lib/rules/prefer-numeric-literals.js b/tests/lib/rules/prefer-numeric-literals.js
@@ -32,16 +32,39 @@ ruleTester.run("prefer-numeric-literals", rule, {
     invalid: [
         {
             code: "parseInt(\"111110111\", 2) === 503;",
+            output: "0b111110111 === 503;",
             parserOptions: { ecmaVersion: 6 },
             errors: [{ message: "Use binary literals instead of parseInt()." }]
         }, {
             code: "parseInt(\"767\", 8) === 503;",
+            output: "0o767 === 503;",
             parserOptions: { ecmaVersion: 6 },
             errors: [{ message: "Use octal literals instead of parseInt()." }]
         }, {
             code: "parseInt(\"1F7\", 16) === 255;",
+            output: "0x1F7 === 255;",
             parserOptions: { ecmaVersion: 6 },
             errors: [{ message: "Use hexadecimal literals instead of parseInt()." }]
+        }, {
+            code: "parseInt('7999', 8);",
+            output: "parseInt('7999', 8);", // not fixed, unexpected 9 in parseInt string
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "Use octal literals instead of parseInt()." }]
+        }, {
+            code: "parseInt('1234', 2);",
+            output: "parseInt('1234', 2);", // not fixed, invalid binary string
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "Use binary literals instead of parseInt()." }]
+        }, {
+            code: "parseInt('1234.5', 8);",
+            output: "parseInt('1234.5', 8);", // not fixed, this isn't an integer
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "Use octal literals instead of parseInt()." }]
+        }, {
+            code: "parseInt('1️⃣3️⃣3️⃣7️⃣', 16);",
+            output: "parseInt('1️⃣3️⃣3️⃣7️⃣', 16);", // not fixed, javascript doesn't support emoji literals
+            parserOptions: { ecmaVersion: 6 },
+            errors: [{ message: "Use hexadecimal literals instead of parseInt()."}]
         }
     ]
 });
