Extract rule: template-no-extra-mut-helper-argument

Author: NullVoxPopuli

README.md

@@ -309,6 +309,12 @@ rules in templates can be disabled with eslint directives with mustache or html
 | [no-runloop](docs/rules/no-runloop.md)                                                                                 | disallow usage of `@ember/runloop` functions                                                                                  | ✅  |    |    |
 | [require-fetch-import](docs/rules/require-fetch-import.md)                                                             | enforce explicit import for `fetch()`                                                                                         |    |    |    |
 
+### Possible Errors
+
+| Name                                                                                         | Description                                               | 💼 | 🔧 | 💡 |
+| :------------------------------------------------------------------------------------------- | :-------------------------------------------------------- | :- | :- | :- |
+| [template-no-extra-mut-helper-argument](docs/rules/template-no-extra-mut-helper-argument.md) | disallow passing more than one argument to the mut helper |    |    |    |
+
 ### Routes
 
 | Name                                                                               | Description                                                                              | 💼 | 🔧 | 💡 |

docs/rules/template-no-extra-mut-helper-argument.md

@@ -0,0 +1,29 @@
+# ember/template-no-extra-mut-helper-argument
+
+<!-- end auto-generated rule header -->
+
+Disallows passing more than one argument to the `mut` helper.
+
+A common mistake when using the Ember handlebars template `mut(attr)` helper is to pass an extra `value` parameter to it when only `attr` should be passed. Instead, the `value` should be passed outside of `mut`.
+
+## Examples
+
+This rule **forbids** the following:
+
+```hbs
+{{my-component click=(action (mut isClicked true))}}
+```
+
+This rule **allows** the following:
+
+```hbs
+{{my-component click=(action (mut isClicked) true)}}
+```
+
+## Related Rules
+
+- [template-no-mut-helper](template-no-mut-helper.md)
+
+## References
+
+- See the [documentation](https://emberjs.com/api/ember/release/classes/Ember.Templates.helpers/methods/mut?anchor=mut) for the Ember handlebars template `mut` helper

lib/rules/template-no-extra-mut-helper-argument.js

@@ -0,0 +1,39 @@
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow passing more than one argument to the mut helper',
+      category: 'Possible Errors',
+      recommended: true,
+      strictGjs: true,
+      strictGts: true,
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-extra-mut-helper-argument.md',
+    },
+    fixable: null,
+    schema: [],
+    messages: {},
+  },
+
+  create(context) {
+    const ERROR_MESSAGE =
+      'The handlebars `mut(attr)` helper should only have one argument passed to it. To pass a value, use: `(action (mut attr) value)`.';
+
+    return {
+      GlimmerSubExpression(node) {
+        if (
+          node.path &&
+          node.path.type === 'GlimmerPathExpression' &&
+          node.path.original === 'mut'
+        ) {
+          if (node.params && node.params.length > 1) {
+            context.report({
+              node,
+              message: ERROR_MESSAGE,
+            });
+          }
+        }
+      },
+    };
+  },
+};

tests/lib/rules/template-no-extra-mut-helper-argument.js

@@ -0,0 +1,49 @@
+const rule = require('../../../lib/rules/template-no-extra-mut-helper-argument');
+const RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+ruleTester.run('template-no-extra-mut-helper-argument', rule, {
+  valid: [
+    '<template>{{my-component click=(action (mut isClicked))}}</template>',
+    '<template>{{my-component click=(action (mut isClicked) true)}}</template>',
+    '<template>{{my-component isClickedMutable=(mut isClicked)}}</template>',
+    '<template><button {{action (mut isClicked)}}></button></template>',
+    '<template><button {{action (mut isClicked) true}}></button></template>',
+  ],
+  invalid: [
+    {
+      code: '<template>{{my-component click=(action (mut isClicked true))}}</template>',
+      output: null,
+      errors: [
+        {
+          message:
+            'The handlebars `mut(attr)` helper should only have one argument passed to it. To pass a value, use: `(action (mut attr) value)`.',
+        },
+      ],
+    },
+    {
+      code: '<template>{{my-component isClickedMutable=(mut isClicked true)}}</template>',
+      output: null,
+      errors: [
+        {
+          message:
+            'The handlebars `mut(attr)` helper should only have one argument passed to it. To pass a value, use: `(action (mut attr) value)`.',
+        },
+      ],
+    },
+    {
+      code: '<template><button {{action (mut isClicked true)}}></button></template>',
+      output: null,
+      errors: [
+        {
+          message:
+            'The handlebars `mut(attr)` helper should only have one argument passed to it. To pass a value, use: `(action (mut attr) value)`.',
+        },
+      ],
+    },
+  ],
+});