Merge pull request #2499 from johanrd/fix/2414

Post-merge review of #2414 (`template-no-capital-arguments`)

Author: NullVoxPopuli

lib/rules/template-no-capital-arguments.js

@@ -1,3 +1,6 @@
+const RESERVED = new Set(['@arguments', '@args', '@block', '@else']);
+const ALLOWED_PREFIX = /^[a-z]/;
+
 /** @type {import('eslint').Rule.RuleModule} */
 module.exports = {
   meta: {
@@ -13,34 +16,48 @@ module.exports = {
     messages: {
       noCapitalArguments:
         'Argument names should start with lowercase. Use @{{lowercase}} instead of @{{name}}.',
+      reservedArgument: '{{name}} is a reserved argument name, try to use another.',
     },
     strictGjs: true,
     strictGts: true,
   },
 
   create(context) {
-    function checkPath(node, path) {
-      if (!path || !path.head) {
+    function checkArgName(node, name) {
+      if (!name || !name.startsWith('@')) {
         return;
       }
 
-      const name = path.head.name || path.head;
-      if (typeof name === 'string' && name.startsWith('@') && /^@[A-Z]/.test(name)) {
-        const lowercase = name.charAt(0) + name.charAt(1).toLowerCase() + name.slice(2);
+      const part = name.slice(1);
+      const firstChar = part.charAt(0);
+
+      if (RESERVED.has(name)) {
+        context.report({
+          node,
+          messageId: 'reservedArgument',
+          data: { name },
+        });
+      } else if (!ALLOWED_PREFIX.test(firstChar)) {
+        const lowercase = `@${firstChar.toLowerCase()}${part.slice(1)}`;
         context.report({
           node,
           messageId: 'noCapitalArguments',
-          data: {
-            name,
-            lowercase,
-          },
+          data: { name, lowercase },
         });
       }
     }
 
     return {
       GlimmerPathExpression(node) {
-        checkPath(node, node);
+        const name = node.original || (node.head && (node.head.name || node.head));
+        if (typeof name === 'string' && name.startsWith('@')) {
+          checkArgName(node, name);
+        }
+      },
+      GlimmerAttrNode(node) {
+        if (node.name && node.name.startsWith('@')) {
+          checkArgName(node, node.name);
+        }
       },
     };
   },

tests/lib/rules/template-no-capital-arguments.js

@@ -18,7 +18,6 @@ ruleTester.run('template-no-capital-arguments', rule, {
           </template>
         }
       `,
-      output: null,
     },
     {
       filename: 'my-component.gjs',
@@ -30,11 +29,35 @@ ruleTester.run('template-no-capital-arguments', rule, {
           </template>
         }
       `,
-      output: null,
+    },
+    // @name in attribute position (lowercase) is valid
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <Foo @name="bar" />
+          </template>
+        }
+      `,
+    },
+    // Nested lowercase path is valid
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <div>{{@arg.nested}}</div>
+          </template>
+        }
+      `,
     },
   ],
 
   invalid: [
+    // Capital path expression
     {
       filename: 'my-component.gjs',
       code: `
@@ -46,11 +69,7 @@ ruleTester.run('template-no-capital-arguments', rule, {
         }
       `,
       output: null,
-      errors: [
-        {
-          messageId: 'noCapitalArguments',
-        },
-      ],
+      errors: [{ messageId: 'noCapitalArguments' }],
     },
     {
       filename: 'my-component.gjs',
@@ -63,11 +82,116 @@ ruleTester.run('template-no-capital-arguments', rule, {
         }
       `,
       output: null,
-      errors: [
-        {
-          messageId: 'noCapitalArguments',
-        },
-      ],
+      errors: [{ messageId: 'noCapitalArguments' }],
+    },
+    // Capital attr node
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <Foo @Name="bar" />
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'noCapitalArguments' }],
+    },
+    // Nested capital path
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <div>{{@Arg.nested}}</div>
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'noCapitalArguments' }],
+    },
+    // Underscore prefix
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <div>{{@_Name}}</div>
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'noCapitalArguments' }],
+    },
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <Foo @_ame="bar" />
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'noCapitalArguments' }],
+    },
+    // Reserved arguments in path expression
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <div>{{@arguments}}</div>
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'reservedArgument' }],
+    },
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <div>{{@args}}</div>
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'reservedArgument' }],
+    },
+    // Reserved arguments in attr position
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <Foo @arguments={{42}} />
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'reservedArgument' }],
+    },
+    {
+      filename: 'my-component.gjs',
+      code: `
+        import Component from '@glimmer/component';
+        export default class MyComponent extends Component {
+          <template>
+            <Foo @block={{42}} />
+          </template>
+        }
+      `,
+      output: null,
+      errors: [{ messageId: 'reservedArgument' }],
     },
   ],
 });