feat(rule): add require-func-head in recommended (#62)

Author: clarkdo

README.md

@@ -102,4 +102,5 @@ Include all the below rules, as well as all priority rules in above categories,
 
 |    | Rule ID | Description |
 |:---|:--------|:------------|
-| :wrench: | [nuxt/no-timing-in-fetch-data](./docs/rules/no-timing-in-fetch-data.md) | Disallow `setTimeout/setInterval` in `asyncData/fetch` |
+|  | [nuxt/no-timing-in-fetch-data](./docs/rules/no-timing-in-fetch-data.md) | Disallow `setTimeout/setInterval` in `asyncData/fetch` |
+|  | [nuxt/require-func-head](./docs/rules/require-func-head.md) | Enforce `head` property in component to be a function. |

docs/rules/require-func-head.md

@@ -0,0 +1,40 @@
+# nuxt/require-func-head
+
+> enforce `head` property in component to be a function.
+
+- :gear: This rule is included in `"plugin:nuxt/recommended"`.
+
+## Rule Details
+
+This rule is enforcing `head` property in component to be a function.
+
+Examples of **incorrect** code for this rule:
+
+```js
+
+export default {
+  head: {
+    title: "My page"
+  }
+}
+
+```
+
+Examples of **correct** code for this rule:
+
+```js
+
+export default {
+  head() {
+    return {
+      title: "My page"
+    }
+  }
+}
+
+```
+
+## :mag: Implementation
+
+- [Rule source](../../lib/rules/require-func-head.js)
+- [Test source](../../lib/rules/__tests__/require-func-head.test.js)

lib/configs/recommended.js

@@ -1,6 +1,7 @@
 module.exports = {
   extends: require.resolve('./base.js'),
   rules: {
-    'nuxt/no-timing-in-fetch-data': 'error'
+    'nuxt/no-timing-in-fetch-data': 'error',
+    'nuxt/require-func-head': 'error'
   }
 }

lib/index.js

@@ -5,7 +5,8 @@ module.exports = {
     'no-globals-in-created': require('./rules/no-globals-in-created'),
     'no-this-in-fetch-data': require('./rules/no-this-in-fetch-data'),
     'no-timing-in-fetch-data': require('./rules/no-timing-in-fetch-data'),
-    'no-cjs-in-config': require('./rules/no-cjs-in-config')
+    'no-cjs-in-config': require('./rules/no-cjs-in-config'),
+    'require-func-head': require('./rules/require-func-head')
   },
   configs: {
     base: require('./configs/base'),

lib/rules/__tests__/require-func-head.test.js

@@ -0,0 +1,60 @@
+/**
+ * @fileoverview disallow `setTimeout/setInterval` in `asyncData/fetch`
+ * @author Xin Du <clark.duxin@gmail.com>
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+var rule = require('../require-func-head')
+
+var RuleTester = require('eslint').RuleTester
+
+const parserOptions = {
+  ecmaVersion: 2018,
+  sourceType: 'module'
+}
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+var ruleTester = new RuleTester()
+ruleTester.run('require-func-head', rule, {
+
+  valid: [
+    {
+      filename: 'test.vue',
+      code: `
+        export default {
+          head() {
+            return {
+              title: "My page"
+            }
+          }
+        }
+      `,
+      parserOptions
+    }
+  ],
+
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: `
+        export default {
+          head: {
+            title: "My page"
+          }
+        }
+      `,
+      errors: [{
+        message: '`head` property in component must be a function.',
+        type: 'Property'
+      }],
+      parserOptions
+    }
+  ]
+})

lib/rules/require-func-head.js

@@ -0,0 +1,54 @@
+/**
+ * @fileoverview enforce component's head property to be a function.
+ * @author Xin Du <clark.duxin@gmail.com>
+ */
+'use strict'
+
+const utils = require('../utils')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    docs: {
+      description: "enforce component's head property to be a function",
+      category: 'recommended'
+    },
+    fixable: 'code',
+    messages: {
+      head: '`head` property in component must be a function.'
+    }
+  },
+
+  create (context) {
+    const sourceCode = context.getSourceCode()
+
+    return utils.executeOnVueComponent(context, (obj) => {
+      obj.properties
+        .filter(p =>
+          p.type === 'Property' &&
+          p.key.type === 'Identifier' &&
+          p.key.name === 'head' &&
+          p.value.type !== 'FunctionExpression' &&
+          p.value.type !== 'ArrowFunctionExpression' &&
+          p.value.type !== 'Identifier'
+        )
+        .forEach(p => {
+          context.report({
+            node: p,
+            messageId: 'head',
+            fix (fixer) {
+              const tokens = utils.getFirstAndLastTokens(p.value, sourceCode)
+
+              return [
+                fixer.insertTextBefore(tokens.first, 'function() {\nreturn '),
+                fixer.insertTextAfter(tokens.last, ';\n}')
+              ]
+            }
+          })
+        })
+    })
+  }
+}

lib/utils/index.js

@@ -43,6 +43,28 @@ module.exports = Object.assign(
           }
         }
       }
+    },
+    isOpenParen (token) {
+      return token.type === 'Punctuator' && token.value === '('
+    },
+    isCloseParen (token) {
+      return token.type === 'Punctuator' && token.value === ')'
+    },
+    getFirstAndLastTokens (node, sourceCode) {
+      let first = sourceCode.getFirstToken(node)
+      let last = sourceCode.getLastToken(node)
+
+      // If the value enclosed by parentheses, update the 'first' and 'last' by the parentheses.
+      while (true) {
+        const prev = sourceCode.getTokenBefore(first)
+        const next = sourceCode.getTokenAfter(last)
+        if (this.isOpenParen(prev) && this.isCloseParen(next)) {
+          first = prev
+          last = next
+        } else {
+          return { first, last }
+        }
+      }
     }
   },
   utils