New: Add vue/single-attribute-single-line rule

docs/rules/single-attribute-single-line.md

@@ -0,0 +1,67 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/single-attribute-single-line
+description: enforce component opening tags with a single attribute to be on a single line
+since: v7.5.0
+---
+# vue/single-attribute-single-line
+
+> enforce component opening tags with a single attribute to be on a single line
+
+- :wrench: The `--fix` option on the [command line](https://eslint.org/docs/user-guide/command-line-interface#fixing-problems) can automatically fix some of the problems reported by this rule.
+
+Ensures that component opening tags that only have one attribute are inline to improve readability.
+
+## :book: Rule Details
+
+This rule aims to enforce component opening tags with a single attribute to be place on a single line.
+It checks all the elements in a template and verifies that when the number of attributes for a component is 1, that it is inlined on the opening tag.
+
+<eslint-code-block fix :rules="{'vue/single-attribute-single-line': ['error']}">
+
+```vue
+<template>
+  <!-- ✓ GOOD -->
+  <MyComponent lorem="1"/>
+  <MyComponent lorem="1" />
+  <MyComponent lorem="1"></MyComponent>
+  <MyComponent lorem="1">
+    <p>content</p>
+  </MyComponent>
+
+  <!-- ✗ BAD -->
+  <MyComponent
+    lorem="1"
+  />
+  <MyComponent
+    lorem="1"
+  ></MyComponent>
+  <MyComponent
+    lorem="1"
+  >
+    <p>content</p>
+  </MyComponent>
+</template>
+```
+
+</eslint-code-block>
+
+## :wrench: Options
+
+```json
+{
+  "vue/single-attribute-single-line": ["error"]
+}
+```
+
+</eslint-code-block>
+
+## :rocket: Version
+
+This rule was introduced in eslint-plugin-vue v7.5.0
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/single-attribute-single-line.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/single-attribute-single-line.js)

lib/rules/single-attribute-single-line.js

@@ -0,0 +1,78 @@
+/**
+ * @fileoverview Enforce component opening tags with a single attribute to be on a single line
+ * @author Jackson Gross
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+const utils = require('../utils')
+
+module.exports = {
+  meta: {
+    type: 'layout',
+    docs: {
+      description:
+        'enforce component opening tags with a single attribute to be on a single line',
+      categories: undefined,
+      url: 'https://eslint.vuejs.org/rules/single-attribute-single-line.html'
+    },
+    fixable: 'whitespace', // or "code" or "whitespace"
+    schema: []
+  },
+  /** @param {RuleContext} context */
+  create(context) {
+    const sourceCode = context.getSourceCode()
+    const template =
+      context.parserServices.getTemplateBodyTokenStore &&
+      context.parserServices.getTemplateBodyTokenStore()
+
+    return utils.defineTemplateBodyVisitor(context, {
+      VStartTag(node) {
+        const closingTag = node.range[1] - 1
+        const numberOfAttributes = node.attributes.length
+
+        if (numberOfAttributes !== 1) return
+
+        if (!utils.isSingleLine(node)) {
+          // Find the closest token before the current prop
+          // that is not a white space
+          const prevToken = /** @type {Token} */ (template.getTokenBefore(
+            node.attributes[0],
+            {
+              filter: (token) => token.type !== 'HTMLWhitespace'
+            }
+          ))
+
+          const startOfAttribute = node.attributes[0].range[0]
+          const endOfAttribute = node.attributes[0].range[1]
+
+          /** @type {Range} */
+          const rangeBetweenAttributeAndStartTag = [
+            prevToken.range[1],
+            startOfAttribute
+          ]
+
+          /** @type {Range} */
+          const rangeBetweenAttributeAndClosingTag = [
+            endOfAttribute,
+            closingTag
+          ]
+
+          context.report({
+            node,
+            message: "'{{name}}' should be on a single line.",
+            data: { name: sourceCode.getText(node.attributes[0].key) },
+            fix(fixer) {
+              return [
+                fixer.replaceTextRange(rangeBetweenAttributeAndClosingTag, ''),
+                fixer.replaceTextRange(rangeBetweenAttributeAndStartTag, ' ')
+              ]
+            }
+          })
+        }
+      }
+    })
+  }
+}

tests/lib/rules/single-attribute-single-line.js

@@ -0,0 +1,155 @@
+/**
+ * @fileoverview Enforce component opening tags with a single attribute to be on a single line
+ * @author Jackson Gross
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/single-attribute-single-line')
+
+// ------------------------------------------------------------------------------
+// Tests
+// ------------------------------------------------------------------------------
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: { ecmaVersion: 2015 }
+})
+
+ruleTester.run('single-attribute-single-line', rule, {
+  valid: [
+    {
+      code: `<template><component></component></template>`
+    },
+    {
+      code: `<template><component /></template>`
+    },
+    {
+      code: `<template>
+        <component></component>
+      </template>`
+    },
+    {
+      code: `<template>
+        <component />
+      </template>`
+    },
+    {
+      code: `<template><component name="John Doe"></component></template>`
+    },
+    {
+      code: `<template><component name="John Doe"/></template>`
+    },
+    {
+      code: `<template>
+        <component name="John Doe"></component>
+      </template>`
+    },
+    {
+      code: `<template>
+        <component name="John Doe" />
+      </template>`
+    },
+    {
+      code: `<template>
+        <component name="John Doe">
+          <p>Some content</p>
+        </component>
+      </template>`
+    },
+    {
+      code: `<template>
+        <component
+          name="John Doe"
+          age="12"
+        >
+          <p>Some content</p>
+        </component>
+      </template>`
+    }
+  ],
+
+  invalid: [
+    {
+      code: `<template>
+        <component
+          name="John Doe"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component name="John Doe"></component>
+      </template>`,
+      errors: ["'name' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          :name="user.name"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component :name="user.name"></component>
+      </template>`,
+      errors: ["':name' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          v-bind="user"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component v-bind="user"></component>
+      </template>`,
+      errors: ["'v-bind' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          @buy="buyProduct"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component @buy="buyProduct"></component>
+      </template>`,
+      errors: ["'@buy' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          @click.stop
+        ></component>
+      </template>`,
+      output: `<template>
+        <component @click.stop></component>
+      </template>`,
+      errors: ["'@click.stop' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          v-if="something"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component v-if="something"></component>
+      </template>`,
+      errors: ["'v-if' should be on a single line."]
+    },
+    {
+      code: `<template>
+        <component
+          v-bind:name="user.name"
+        ></component>
+      </template>`,
+      output: `<template>
+        <component v-bind:name="user.name"></component>
+      </template>`,
+      errors: ["'v-bind:name' should be on a single line."]
+    }
+  ]
+})