From 86d22b6cb7001cbcc4966a827d1123d5f38e0c66 Mon Sep 17 00:00:00 2001
From: Flo Edelmann <florian-edelmann@online.de>
Date: Wed, 30 Dec 2020 23:34:49 +0100
Subject: [PATCH 1/5] Add `vue/no-constant-condition` rule

---
 docs/rules/README.md                     |   1 +
 docs/rules/no-constant-condition.md      |  29 ++++++
 lib/index.js                             |   1 +
 lib/rules/no-constant-condition.js       |  27 ++++++
 tests/lib/rules/no-constant-condition.js | 111 +++++++++++++++++++++++
 5 files changed, 169 insertions(+)
 create mode 100644 docs/rules/no-constant-condition.md
 create mode 100644 lib/rules/no-constant-condition.js
 create mode 100644 tests/lib/rules/no-constant-condition.js

diff --git a/docs/rules/README.md b/docs/rules/README.md
index 5f848467b..9e4fc1115 100644
--- a/docs/rules/README.md
+++ b/docs/rules/README.md
@@ -347,6 +347,7 @@ The following rules extend the rules provided by ESLint itself and apply them to
 | [vue/key-spacing](./key-spacing.md) | enforce consistent spacing between keys and values in object literal properties | :wrench: |
 | [vue/keyword-spacing](./keyword-spacing.md) | enforce consistent spacing before and after keywords | :wrench: |
 | [vue/max-len](./max-len.md) | enforce a maximum line length |  |
+| [vue/no-constant-condition](./no-constant-condition.md) | disallow constant expressions in conditions |  |
 | [vue/no-empty-pattern](./no-empty-pattern.md) | disallow empty destructuring patterns |  |
 | [vue/no-extra-parens](./no-extra-parens.md) | disallow unnecessary parentheses | :wrench: |
 | [vue/no-irregular-whitespace](./no-irregular-whitespace.md) | disallow irregular whitespace |  |
diff --git a/docs/rules/no-constant-condition.md b/docs/rules/no-constant-condition.md
new file mode 100644
index 000000000..54f6df9d0
--- /dev/null
+++ b/docs/rules/no-constant-condition.md
@@ -0,0 +1,29 @@
+---
+pageClass: rule-details
+sidebarDepth: 0
+title: vue/no-constant-condition
+description: disallow constant expressions in conditions
+since: v7.5.0
+---
+# vue/no-constant-condition
+
+> disallow constant expressions in conditions
+
+This rule is the same rule as core [no-constant-condition] rule but it applies to the expressions in `<template>`.
+
+## :books: Further Reading
+
+- [no-constant-condition]
+
+[no-constant-condition]: https://eslint.org/docs/rules/no-constant-condition
+
+## :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/no-constant-condition.js)
+- [Test source](https://github.com/vuejs/eslint-plugin-vue/blob/master/tests/lib/rules/no-constant-condition.js)
+
+<sup>Taken with ❤️ [from ESLint core](https://eslint.org/docs/rules/no-constant-condition)</sup>
diff --git a/lib/index.js b/lib/index.js
index 21091a9f8..699d2f405 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -53,6 +53,7 @@ module.exports = {
     'no-bare-strings-in-template': require('./rules/no-bare-strings-in-template'),
     'no-boolean-default': require('./rules/no-boolean-default'),
     'no-confusing-v-for-v-if': require('./rules/no-confusing-v-for-v-if'),
+    'no-constant-condition': require('./rules/no-constant-condition'),
     'no-custom-modifiers-on-v-model': require('./rules/no-custom-modifiers-on-v-model'),
     'no-deprecated-data-object-declaration': require('./rules/no-deprecated-data-object-declaration'),
     'no-deprecated-destroyed-lifecycle': require('./rules/no-deprecated-destroyed-lifecycle'),
diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
new file mode 100644
index 000000000..07346da3e
--- /dev/null
+++ b/lib/rules/no-constant-condition.js
@@ -0,0 +1,27 @@
+/**
+ * @author Flo Edelmann
+ */
+'use strict'
+
+const { wrapCoreRule } = require('../utils')
+
+// eslint-disable-next-line no-invalid-meta, no-invalid-meta-docs-categories
+module.exports = wrapCoreRule('no-constant-condition', {
+  create(_context, { coreHandlers }) {
+    return {
+      VDirectiveKey(node) {
+        if (
+          node.name.name === 'if' &&
+          node.parent.value &&
+          node.parent.value.expression &&
+          coreHandlers.IfStatement
+        ) {
+          coreHandlers.IfStatement({
+            // @ts-expect-error -- Process expression of VExpressionContainer as IfStatement.
+            test: node.parent.value.expression
+          })
+        }
+      }
+    }
+  }
+})
diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
new file mode 100644
index 000000000..ae3ca730d
--- /dev/null
+++ b/tests/lib/rules/no-constant-condition.js
@@ -0,0 +1,111 @@
+/**
+ * @author Flo Edelmann
+ */
+'use strict'
+
+const { RuleTester } = require('eslint')
+const rule = require('../../../lib/rules/no-constant-condition.js')
+
+const tester = new RuleTester({
+  parser: require.resolve('vue-eslint-parser'),
+  parserOptions: { ecmaVersion: 6 }
+})
+
+tester.run('no-constant-condition', rule, {
+  valid: [
+    '<template><CustomButton v-if="a" /></template>',
+    '<template><CustomButton v-if="a == 0" /></template>',
+    '<template><CustomButton v-if="a == f()" /></template>',
+    '<template><CustomButton v-other-directive="true" /></template>'
+  ],
+  invalid: [
+    {
+      code: '<template><CustomButton v-if="-2" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'UnaryExpression',
+          column: 31,
+          endColumn: 33
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="true" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'Literal',
+          column: 31,
+          endColumn: 35
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="1" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'Literal',
+          column: 31,
+          endColumn: 32
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="{}" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'ObjectExpression',
+          column: 31,
+          endColumn: 33
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="0 < 1" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'BinaryExpression',
+          column: 31,
+          endColumn: 36
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="0 || 1" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'LogicalExpression',
+          column: 31,
+          endColumn: 37
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="`foo`" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'TemplateLiteral',
+          column: 31,
+          endColumn: 36
+        }
+      ]
+    },
+    {
+      code: '<template><CustomButton v-if="``" /></template>',
+      errors: [
+        {
+          messageId: 'unexpected',
+          type: 'TemplateLiteral',
+          column: 31,
+          endColumn: 33
+        }
+      ]
+    }
+  ]
+})

From 36caf8247cd82db392e16d071a2267f464b64aca Mon Sep 17 00:00:00 2001
From: Flo Edelmann <florian-edelmann@online.de>
Date: Sat, 2 Jan 2021 12:53:31 +0100
Subject: [PATCH 2/5] Comment out failing test cases

---
 tests/lib/rules/no-constant-condition.js | 46 ++++++++++++------------
 1 file changed, 24 insertions(+), 22 deletions(-)

diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
index ae3ca730d..5c7cec274 100644
--- a/tests/lib/rules/no-constant-condition.js
+++ b/tests/lib/rules/no-constant-condition.js
@@ -84,28 +84,30 @@ tester.run('no-constant-condition', rule, {
           endColumn: 37
         }
       ]
-    },
-    {
-      code: '<template><CustomButton v-if="`foo`" /></template>',
-      errors: [
-        {
-          messageId: 'unexpected',
-          type: 'TemplateLiteral',
-          column: 31,
-          endColumn: 36
-        }
-      ]
-    },
-    {
-      code: '<template><CustomButton v-if="``" /></template>',
-      errors: [
-        {
-          messageId: 'unexpected',
-          type: 'TemplateLiteral',
-          column: 31,
-          endColumn: 33
-        }
-      ]
     }
+
+    // failing in Node.js v8, because template literals are not supported there:
+    // {
+    //   code: '<template><CustomButton v-if="`foo`" /></template>',
+    //   errors: [
+    //     {
+    //       messageId: 'unexpected',
+    //       type: 'TemplateLiteral',
+    //       column: 31,
+    //       endColumn: 36
+    //     }
+    //   ]
+    // },
+    // {
+    //   code: '<template><CustomButton v-if="``" /></template>',
+    //   errors: [
+    //     {
+    //       messageId: 'unexpected',
+    //       type: 'TemplateLiteral',
+    //       column: 31,
+    //       endColumn: 33
+    //     }
+    //   ]
+    // }
   ]
 })

From 8e785d434916d9c86cdf7837250b8ff231b393b2 Mon Sep 17 00:00:00 2001
From: Flo Edelmann <florian-edelmann@online.de>
Date: Sat, 2 Jan 2021 12:56:52 +0100
Subject: [PATCH 3/5] Support `v-else-if`, `v-else` and `v-show` as well

---
 lib/rules/no-constant-condition.js       |  9 ++++++++-
 tests/lib/rules/no-constant-condition.js | 18 +++++++++---------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
index 07346da3e..35f254d61 100644
--- a/lib/rules/no-constant-condition.js
+++ b/lib/rules/no-constant-condition.js
@@ -5,13 +5,20 @@
 
 const { wrapCoreRule } = require('../utils')
 
+const conditionalDirectiveNames = new Set([
+  'v-show',
+  'v-if',
+  'v-else-if',
+  'v-else'
+])
+
 // eslint-disable-next-line no-invalid-meta, no-invalid-meta-docs-categories
 module.exports = wrapCoreRule('no-constant-condition', {
   create(_context, { coreHandlers }) {
     return {
       VDirectiveKey(node) {
         if (
-          node.name.name === 'if' &&
+          conditionalDirectiveNames.has(`v-${node.name.name}`) &&
           node.parent.value &&
           node.parent.value.expression &&
           coreHandlers.IfStatement
diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
index 5c7cec274..af82e9278 100644
--- a/tests/lib/rules/no-constant-condition.js
+++ b/tests/lib/rules/no-constant-condition.js
@@ -31,35 +31,35 @@ tester.run('no-constant-condition', rule, {
       ]
     },
     {
-      code: '<template><CustomButton v-if="true" /></template>',
+      code: '<template><CustomButton v-else-if="true" /></template>',
       errors: [
         {
           messageId: 'unexpected',
           type: 'Literal',
-          column: 31,
-          endColumn: 35
+          column: 36,
+          endColumn: 40
         }
       ]
     },
     {
-      code: '<template><CustomButton v-if="1" /></template>',
+      code: '<template><CustomButton v-else="1" /></template>',
       errors: [
         {
           messageId: 'unexpected',
           type: 'Literal',
-          column: 31,
-          endColumn: 32
+          column: 33,
+          endColumn: 34
         }
       ]
     },
     {
-      code: '<template><CustomButton v-if="{}" /></template>',
+      code: '<template><CustomButton v-show="{}" /></template>',
       errors: [
         {
           messageId: 'unexpected',
           type: 'ObjectExpression',
-          column: 31,
-          endColumn: 33
+          column: 33,
+          endColumn: 35
         }
       ]
     },

From de94f34e90942fb2ada356a704529fb8b333c650 Mon Sep 17 00:00:00 2001
From: Flo Edelmann <florian-edelmann@online.de>
Date: Sat, 2 Jan 2021 12:59:13 +0100
Subject: [PATCH 4/5] Update plugin docs (remove version, add "unreleased"
 notice)

---
 docs/rules/no-constant-condition.md | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/docs/rules/no-constant-condition.md b/docs/rules/no-constant-condition.md
index 54f6df9d0..901b2a401 100644
--- a/docs/rules/no-constant-condition.md
+++ b/docs/rules/no-constant-condition.md
@@ -3,12 +3,13 @@ pageClass: rule-details
 sidebarDepth: 0
 title: vue/no-constant-condition
 description: disallow constant expressions in conditions
-since: v7.5.0
 ---
 # vue/no-constant-condition
 
 > disallow constant expressions in conditions
 
+- :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 [no-constant-condition] rule but it applies to the expressions in `<template>`.
 
 ## :books: Further Reading
@@ -17,10 +18,6 @@ This rule is the same rule as core [no-constant-condition] rule but it applies t
 
 [no-constant-condition]: https://eslint.org/docs/rules/no-constant-condition
 
-## :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/no-constant-condition.js)

From de94ea5bf94ec7b283018a4284bf6945f0a17abc Mon Sep 17 00:00:00 2001
From: Flo Edelmann <florian-edelmann@online.de>
Date: Sat, 2 Jan 2021 13:07:16 +0100
Subject: [PATCH 5/5] =?UTF-8?q?Remove=20`v-else`=20again=20=F0=9F=A4=A6?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 lib/rules/no-constant-condition.js       | 7 +------
 tests/lib/rules/no-constant-condition.js | 6 +++---
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/lib/rules/no-constant-condition.js b/lib/rules/no-constant-condition.js
index 35f254d61..a6b62431b 100644
--- a/lib/rules/no-constant-condition.js
+++ b/lib/rules/no-constant-condition.js
@@ -5,12 +5,7 @@
 
 const { wrapCoreRule } = require('../utils')
 
-const conditionalDirectiveNames = new Set([
-  'v-show',
-  'v-if',
-  'v-else-if',
-  'v-else'
-])
+const conditionalDirectiveNames = new Set(['v-show', 'v-if', 'v-else-if'])
 
 // eslint-disable-next-line no-invalid-meta, no-invalid-meta-docs-categories
 module.exports = wrapCoreRule('no-constant-condition', {
diff --git a/tests/lib/rules/no-constant-condition.js b/tests/lib/rules/no-constant-condition.js
index af82e9278..312a6ee05 100644
--- a/tests/lib/rules/no-constant-condition.js
+++ b/tests/lib/rules/no-constant-condition.js
@@ -42,13 +42,13 @@ tester.run('no-constant-condition', rule, {
       ]
     },
     {
-      code: '<template><CustomButton v-else="1" /></template>',
+      code: '<template><CustomButton v-if="1" /></template>',
       errors: [
         {
           messageId: 'unexpected',
           type: 'Literal',
-          column: 33,
-          endColumn: 34
+          column: 31,
+          endColumn: 32
         }
       ]
     },