Create vue/multiline-ternary extension rule

docs/rules/multiline-ternary.md

@@ -0,0 +1,19 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/multiline-ternary
+description: Enforce newlines between operands of ternary expressions in `<template>` 
+---
+# vue/multiline-ternary
+
+- :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.
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> ***This rule has not been released yet.*** </badge>
+
+This rule is the same rule as core [multiline-ternary] rule but it applies to the expressions in `<template>`.
+
+## :books: Further Reading
+
+- [multiline-ternary]
+
+[multiline-ternary]: https://eslint.org/docs/rules/multiline-ternary

lib/rules/multiline-ternary.js

@@ -0,0 +1,16 @@
+/**
+ * @author dev1437
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+// ------------------------------------------------------------------------------
+// Requirements
+// ------------------------------------------------------------------------------
+
+const { wrapCoreRule } = require('../utils')
+
+// eslint-disable-next-line no-invalid-meta, no-invalid-meta-docs-categories
+module.exports = wrapCoreRule('multiline-ternary', {
+  skipDynamicArguments: true
+})

tests/lib/rules/multiline-ternary.js

@@ -0,0 +1,143 @@
+/**
+ * @author dev1437
+ * See LICENSE file in root directory for full license.
+ */
+'use strict'
+
+const RuleTester = require('eslint').RuleTester
+const rule = require('../../../lib/rules/multiline-ternary')
+
+const tester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: {
+    ecmaVersion: 2020,
+    sourceType: 'module'
+  }
+})
+
+tester.run('multiline-ternary', rule, {
+  valid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ?
+            aVeryLongOutput :
+            thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ? aVeryLongOutput : thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `,
+      options: ['never']
+    }
+  ],
+  invalid: [
+    {
+      filename: 'test.vue',
+      code: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ?
+            aVeryLongOutput : thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `,
+      output: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ?
+            aVeryLongOutput
+: thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `,
+      errors: [
+        {
+          message:
+            'Expected newline between consequent and alternate of ternary expression.',
+          line: 5,
+          column: 13
+        }
+      ],
+      options: ['always-multiline']
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ?
+            aVeryLongOutput : thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `,
+      output: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ?aVeryLongOutput : thisCantFitOnASingleLine
+        }">
+        </div>
+      </template>
+      `,
+      errors: [
+        {
+          message:
+            'Unexpected newline between test and consequent of ternary expression.',
+          line: 4,
+          column: 19
+        }
+      ],
+      options: ['never']
+    },
+    {
+      filename: 'test.vue',
+      code: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition ? aVeryLongOutput : thisCantFitOnASingleLine
+         }">
+        </div>
+      </template>
+      `,
+      output: `
+      <template>
+        <div :class="{
+          'test': someReallyLongCondition
+? aVeryLongOutput
+: thisCantFitOnASingleLine
+         }">
+        </div>
+      </template>
+      `,
+      errors: [
+        {
+          message:
+            'Expected newline between test and consequent of ternary expression.',
+          line: 4,
+          column: 19
+        },
+        {
+          message:
+            'Expected newline between consequent and alternate of ternary expression.',
+          line: 4,
+          column: 45
+        }
+      ]
+    }
+  ]
+})