New: add rule no-plusplus (#13)

lib/rules/no-plusplus.js

@@ -0,0 +1,27 @@
+/**
+ * @fileoverview add fixer to rule no-plusplus
+ * @author 唯然<weiran.zsd@outlook.com>
+ */
+"use strict";
+
+const ruleComposer = require("eslint-rule-composer");
+const utils = require("../utils");
+
+const rule = utils.getFixableRule("no-plusplus");
+const fixableTypes = new Set(["ExpressionStatement", "ForStatement"]);
+
+module.exports = ruleComposer.mapReports(
+    rule,
+    problem => {
+        const node = problem.node;
+        const op = node.operator === "++" ? "+=1" : "-=1";
+
+        problem.fix = function(fixer) {
+            return fixableTypes.has(node.parent.type)
+                ? fixer.replaceText(node, `${node.argument.name}${op}`)
+                : null;
+        };
+
+        return problem;
+    }
+);

readme.md

@@ -35,6 +35,7 @@ Name | 🛠 | Description
 [no-alert](https://eslint.org/docs/rules/no-alert) | 🛠 | disallow the use of `alert`, `confirm`, and `prompt`
 [no-console](https://eslint.org/docs/rules/no-console) | 🛠 | disallow the use of `console`
 [no-debugger](https://eslint.org/docs/rules/no-debugger) | 🛠 | disallow the use of `debugger`
+[no-plusplus](https://eslint.org/docs/rules/no-plusplus) | 🛠 | disallow the unary operators `++` and `--`
 [prefer-spread](https://eslint.org/docs/rules/prefer-spread) | 🛠 | require spread operators instead of `.apply()`
 [valid-typeof](https:/eslint.org/docs/rules/valid-typeof) | 🛠 | enforce comparing `typeof` expressions against valid strings
 <!-- __END AUTOGENERATED TABLE__ -->

tests/lib/rules/no-plusplus.js

@@ -0,0 +1,66 @@
+/**
+ * @fileoverview Tests for no-plusplus.
+ * @author 唯然<weiran.zsd@outlook.com>
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require("../../../lib/rules/no-plusplus"),
+    RuleTester = require("eslint").RuleTester;
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester();
+
+ruleTester.run("no-plusplus", rule, {
+    valid: [
+        "var foo = 0; foo=+1;",
+
+        // With "allowForLoopAfterthoughts" allowed
+        { code: "var foo = 0; foo=+1;", options: [{ allowForLoopAfterthoughts: true }] },
+        { code: "for (i = 0; i < l; i++) { console.log(i); }", options: [{ allowForLoopAfterthoughts: true }] }
+    ],
+
+    invalid: [
+        {
+            code: "var foo = 0; foo++;",
+            output: "var foo = 0; foo+=1;",
+            errors: [{ message: "Unary operator '++' used.", type: "UpdateExpression" }]
+        },
+        {
+            code: "var foo = 0; foo--;",
+            output: "var foo = 0; foo-=1;",
+            errors: [{ message: "Unary operator '--' used.", type: "UpdateExpression" }]
+        },
+        {
+            code: "for (i = 0; i < l; i++) { console.log(i); }",
+            output: "for (i = 0; i < l; i+=1) { console.log(i); }",
+            errors: [{ message: "Unary operator '++' used.", type: "UpdateExpression" }]
+        },
+
+        // With "allowForLoopAfterthoughts" allowed
+        {
+            code: "var foo = 0; foo++;",
+            output: "var foo = 0; foo+=1;",
+            options: [{ allowForLoopAfterthoughts: true }],
+            errors: [{ message: "Unary operator '++' used.", type: "UpdateExpression" }]
+        },
+        {
+            code: "for (i = 0; i < l; i++) { v++; }",
+            output: "for (i = 0; i < l; i++) { v+=1; }",
+            options: [{ allowForLoopAfterthoughts: true }],
+            errors: [{ message: "Unary operator '++' used.", type: "UpdateExpression" }]
+        },
+        {
+            code: "var bar = foo++;",
+            output: null,
+            errors: [{ message: "Unary operator '++' used.", type: "UpdateExpression" }]
+        }
+    ]
+});