Add prefer-true-attribute-shorthand rule (#1796)

* Add `prefer-true-attribute-shorthand` rule

* fix typo

* accept suggestions

* accept option `"always"` or `"never"`

* ignore native HTML elements

* provide suggestions instead of auto fix

* meta update

docs/rules/README.md

@@ -353,6 +353,7 @@ For example:
 | [vue/no-v-text](./no-v-text.md) | disallow use of v-text |  |
 | [vue/padding-line-between-blocks](./padding-line-between-blocks.md) | require or disallow padding lines between blocks | :wrench: |
 | [vue/prefer-separate-static-class](./prefer-separate-static-class.md) | require static class names in template to be in a separate `class` attribute | :wrench: |
+| [vue/prefer-true-attribute-shorthand](./prefer-true-attribute-shorthand.md) | require shorthand form attribute when `v-bind` value is `true` | :bulb: |
 | [vue/require-direct-export](./require-direct-export.md) | require the component to be directly exported |  |
 | [vue/require-emit-validator](./require-emit-validator.md) | require type definitions in emits | :bulb: |
 | [vue/require-expose](./require-expose.md) | require declare public properties using `expose` | :bulb: |

docs/rules/prefer-true-attribute-shorthand.md

@@ -0,0 +1,110 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/prefer-true-attribute-shorthand
+description: require shorthand form attribute when `v-bind` value is `true`
+---
+# vue/prefer-true-attribute-shorthand
+
+> require shorthand form attribute when `v-bind` value is `true`
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+- :bulb: Some problems reported by this rule are manually fixable by editor [suggestions](https://eslint.org/docs/developer-guide/working-with-rules#providing-suggestions).
+
+## :book: Rule Details
+
+`v-bind` attribute with `true` value usually can be written in shorthand form. This can reduce verbosity.
+
+<eslint-code-block :rules="{'vue/prefer-true-attribute-shorthand': ['error']}">
+
+```vue
+<template>
+  <!-- ✗ BAD -->
+  <MyComponent v-bind:show="true" />
+  <MyComponent :show="true" />
+
+  <!-- ✓ GOOD -->
+  <MyComponent show />
+  <MyComponent another-prop="true" />
+</template>
+```
+
+</eslint-code-block>
+
+::: warning Warning
+The shorthand form is not always equivalent! If a prop accepts multiple types, but Boolean is not the first one, a shorthand prop won't pass `true`.
+:::
+
+```vue
+<script>
+export default {
+  name: 'MyComponent',
+  props: {
+    bool: Boolean,
+    boolOrString: [Boolean, String],
+    stringOrBool: [String, Boolean],
+  }
+}
+</script>
+```
+
+**Shorthand form:**
+
+```vue
+<MyComponent bool bool-or-string string-or-bool />
+```
+
+```
+bool: true (boolean)
+boolOrString: true (boolean)
+stringOrBool: "" (string)
+```
+
+**Longhand form:**
+
+```vue
+<MyComponent :bool="true" :bool-or-string="true" :string-or-bool="true" />
+```
+
+```
+bool: true (boolean)
+boolOrString: true (boolean)
+stringOrBool: true (boolean)
+```
+
+Those two calls will introduce different render result. See [this demo](https://sfc.vuejs.org/#eyJBcHAudnVlIjoiPHNjcmlwdCBzZXR1cD5cbmltcG9ydCBNeUNvbXBvbmVudCBmcm9tICcuL015Q29tcG9uZW50LnZ1ZSdcbjwvc2NyaXB0PlxuXG48dGVtcGxhdGU+XG4gIFNob3J0aGFuZCBmb3JtOlxuICA8TXlDb21wb25lbnQgYm9vbCBib29sLW9yLXN0cmluZyBzdHJpbmctb3ItYm9vbCAvPlxuICBcbiAgTG9uZ2hhbmQgZm9ybTpcbiAgPE15Q29tcG9uZW50IDpib29sPVwidHJ1ZVwiIDpib29sLW9yLXN0cmluZz1cInRydWVcIiA6c3RyaW5nLW9yLWJvb2w9XCJ0cnVlXCIgLz5cbjwvdGVtcGxhdGU+IiwiaW1wb3J0LW1hcC5qc29uIjoie1xuICBcImltcG9ydHNcIjoge1xuICAgIFwidnVlXCI6IFwiaHR0cHM6Ly9zZmMudnVlanMub3JnL3Z1ZS5ydW50aW1lLmVzbS1icm93c2VyLmpzXCJcbiAgfVxufSIsIk15Q29tcG9uZW50LnZ1ZSI6IjxzY3JpcHQ+XG5leHBvcnQgZGVmYXVsdCB7XG4gIHByb3BzOiB7XG4gICAgYm9vbDogQm9vbGVhbixcbiAgICBib29sT3JTdHJpbmc6IFtCb29sZWFuLCBTdHJpbmddLFxuICAgIHN0cmluZ09yQm9vbDogW1N0cmluZywgQm9vbGVhbl0sXG4gIH1cbn1cbjwvc2NyaXB0PlxuXG48dGVtcGxhdGU+XG4gIDxwcmU+XG5ib29sOiB7e2Jvb2x9fSAoe3sgdHlwZW9mIGJvb2wgfX0pXG5ib29sT3JTdHJpbmc6IHt7Ym9vbE9yU3RyaW5nfX0gKHt7IHR5cGVvZiBib29sT3JTdHJpbmcgfX0pXG5zdHJpbmdPckJvb2w6IHt7c3RyaW5nT3JCb29sfX0gKHt7IHR5cGVvZiBzdHJpbmdPckJvb2wgfX0pXG4gIDwvcHJlPlxuPC90ZW1wbGF0ZT4ifQ==).
+
+## :wrench: Options
+
+Default options is `"always"`.
+
+```json
+{
+  "vue/prefer-true-attribute-shorthand": ["error", "always" | "never"]
+}
+```
+
+- `"always"` (default) ... requires shorthand form.
+- `"never"` ... requires long form.
+
+### `"never"`
+
+<eslint-code-block :rules="{'vue/prefer-true-attribute-shorthand': ['error', 'never']}">
+
+```vue
+<template>
+  <!-- ✗ BAD -->
+  <MyComponent show />
+
+  <!-- ✓ GOOD -->
+  <MyComponent :show="true" />
+  <MyComponent v-bind:show="true" />
+</template>
+```
+
+</eslint-code-block>
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/vuejs/eslint-plugin-vue/blob/master/lib/rules/prefer-true-attribute-shorthand.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/prefer-true-attribute-shorthand.js)

lib/index.js

@@ -159,6 +159,7 @@ module.exports = {
     'padding-line-between-blocks': require('./rules/padding-line-between-blocks'),
     'prefer-separate-static-class': require('./rules/prefer-separate-static-class'),
     'prefer-template': require('./rules/prefer-template'),
+    'prefer-true-attribute-shorthand': require('./rules/prefer-true-attribute-shorthand'),
     'prop-name-casing': require('./rules/prop-name-casing'),
     'quote-props': require('./rules/quote-props'),
     'require-component-is': require('./rules/require-component-is'),

lib/rules/prefer-true-attribute-shorthand.js

@@ -0,0 +1,110 @@
+/**
+ * @author Pig Fang
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const utils = require('../utils')
+
+// ------------------------------------------------------------------------------
+// Rule Definition
+// ------------------------------------------------------------------------------
+
+module.exports = {
+  meta: {
+    type: 'suggestion',
+    docs: {
+      description:
+        'require shorthand form attribute when `v-bind` value is `true`',
+      categories: undefined,
+      url: 'https://eslint.vuejs.org/rules/prefer-true-attribute-shorthand.html'
+    },
+    fixable: null,
+    hasSuggestions: true,
+    schema: [{ enum: ['always', 'never'] }],
+    messages: {
+      expectShort:
+        "Boolean prop with 'true' value should be written in shorthand form.",
+      expectLong:
+        "Boolean prop with 'true' value should be written in long form.",
+      rewriteIntoShort: 'Rewrite this prop into shorthand form.',
+      rewriteIntoLongVueProp:
+        'Rewrite this prop into long-form Vue component prop.',
+      rewriteIntoLongHtmlAttr:
+        'Rewrite this prop into long-form HTML attribute.'
+    }
+  },
+  /** @param {RuleContext} context */
+  create(context) {
+    /** @type {'always' | 'never'} */
+    const option = context.options[0] || 'always'
+
+    return utils.defineTemplateBodyVisitor(context, {
+      VAttribute(node) {
+        if (!utils.isCustomComponent(node.parent.parent)) {
+          return
+        }
+
+        if (option === 'never' && !node.directive && !node.value) {
+          context.report({
+            node,
+            messageId: 'expectLong',
+            suggest: [
+              {
+                messageId: 'rewriteIntoLongVueProp',
+                fix: (fixer) =>
+                  fixer.replaceText(node, `:${node.key.rawName}="true"`)
+              },
+              {
+                messageId: 'rewriteIntoLongHtmlAttr',
+                fix: (fixer) =>
+                  fixer.replaceText(
+                    node,
+                    `${node.key.rawName}="${node.key.rawName}"`
+                  )
+              }
+            ]
+          })
+          return
+        }
+
+        if (option !== 'always') {
+          return
+        }
+
+        if (
+          !node.directive ||
+          !node.value ||
+          !node.value.expression ||
+          node.value.expression.type !== 'Literal' ||
+          node.value.expression.value !== true
+        ) {
+          return
+        }
+
+        const { argument } = node.key
+        if (!argument) {
+          return
+        }
+
+        context.report({
+          node,
+          messageId: 'expectShort',
+          suggest: [
+            {
+              messageId: 'rewriteIntoShort',
+              fix: (fixer) => {
+                const sourceCode = context.getSourceCode()
+                return fixer.replaceText(node, sourceCode.getText(argument))
+              }
+            }
+          ]
+        })
+      }
+    })
+  }
+}