Merge pull request #2591 from NullVoxPopuli/nvp/template-lint-extract-rule-template-no-valueless-arguments

Extract rule: template-no-valueless-arguments

Author: NullVoxPopuli

README.md

@@ -255,6 +255,7 @@ rules in templates can be disabled with eslint directives with mustache or html
 | [template-no-obsolete-elements](docs/rules/template-no-obsolete-elements.md)                                       | disallow obsolete HTML elements                                              |    |    |    |
 | [template-no-outlet-outside-routes](docs/rules/template-no-outlet-outside-routes.md)                               | disallow {{outlet}} outside of route templates                               |    |    |    |
 | [template-no-page-title-component](docs/rules/template-no-page-title-component.md)                                 | disallow usage of ember-page-title component                                 |    |    |    |
+| [template-no-valueless-arguments](docs/rules/template-no-valueless-arguments.md)                                   | disallow valueless named arguments                                           |    |    |    |
 | [template-no-whitespace-for-layout](docs/rules/template-no-whitespace-for-layout.md)                               | disallow using whitespace for layout purposes                                |    |    |    |
 | [template-no-yield-block-params-to-else-inverse](docs/rules/template-no-yield-block-params-to-else-inverse.md)     | disallow yielding block params to else or inverse block                      |    |    |    |
 | [template-no-yield-only](docs/rules/template-no-yield-only.md)                                                     | disallow components that only yield                                          |    |    |    |

docs/rules/template-no-valueless-arguments.md

@@ -0,0 +1,36 @@
+# ember/template-no-valueless-arguments
+
+<!-- end auto-generated rule header -->
+
+Similar to HTML attributes, component arguments will default to an empty string when they are not explicitly assigned a value. This behavior isn't documented anywhere so depending on it isn't recommended and usually the result of a user-error. Since it _is_ valid syntax, accidental use of this behavior can be hard to detect and cause confusing bugs.
+
+## Examples
+
+This rule **forbids** the following:
+
+```gjs
+<template><Editor @defaultText /></template>
+```
+
+```gjs
+<template><SomeComponent @valuelessByAccident{{@canBeAModifier}} /></template>
+```
+
+This rule **allows** the following:
+
+```gjs
+<template><Editor @defaultText="" /></template>
+```
+
+## Migration
+
+Explicitly assign a value to all arguments.
+
+## Related Rules
+
+- [ember/no-quoteless-attributes](no-quoteless-attributes.md)
+
+## References
+
+- [RFC-311: angle bracket invocation](https://emberjs.github.io/rfcs/0311-angle-bracket-invocation.html)
+- [Attributes in the HTML specification](https://html.spec.whatwg.org/#syntax-attributes))

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

@@ -0,0 +1,39 @@
+/** @type {import('eslint').Rule.RuleModule} */
+function isNamedArgument(attrName) {
+  return attrName.startsWith('@');
+}
+
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow valueless named arguments',
+      category: 'Best Practices',
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-valueless-arguments.md',
+      templateMode: 'both',
+    },
+    schema: [],
+    messages: { valueless: 'Named arguments should have an explicitly assigned value.' },
+    originallyFrom: {
+      name: 'ember-template-lint',
+      rule: 'lib/rules/no-valueless-arguments.js',
+      docs: 'docs/rule/no-valueless-arguments.md',
+      tests: 'test/unit/rules/no-valueless-arguments-test.js',
+    },
+  },
+  create(context) {
+    const sourceCode = context.sourceCode || context.getSourceCode();
+
+    return {
+      GlimmerAttrNode(node) {
+        if (!isNamedArgument(node.name)) {
+          return;
+        }
+
+        if (!sourceCode.getText(node).includes('=')) {
+          context.report({ node, messageId: 'valueless' });
+        }
+      },
+    };
+  },
+};

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

@@ -0,0 +1,60 @@
+const rule = require('../../../lib/rules/template-no-valueless-arguments');
+const RuleTester = require('eslint').RuleTester;
+
+const validHbs = [
+  '<SomeComponent @emptyString="" data-test-some-component />',
+  '<button type="submit" disabled {{on "click" this.submit}}></button>',
+];
+
+const invalidHbs = [
+  {
+    code: '<SomeComponent @valueless />',
+    output: null,
+    errors: [{ messageId: 'valueless' }],
+  },
+  {
+    code: '<SomeComponent @valuelessByAccident{{this.canBeAModifier}} />',
+    output: null,
+    errors: [{ messageId: 'valueless' }],
+  },
+  {
+    code: '<SomeComponent @valuelessByAccident{{@canBeAModifier}} />',
+    output: null,
+    errors: [{ messageId: 'valueless' }],
+  },
+];
+
+function wrapTemplate(entry) {
+  if (typeof entry === 'string') {
+    return `<template>${entry}</template>`;
+  }
+
+  return {
+    ...entry,
+    code: `<template>${entry.code}</template>`,
+    output: entry.output ? `<template>${entry.output}</template>` : entry.output,
+  };
+}
+
+const gjsRuleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+gjsRuleTester.run('template-no-valueless-arguments', rule, {
+  valid: validHbs.map(wrapTemplate),
+  invalid: invalidHbs.map(wrapTemplate),
+});
+
+const hbsRuleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser/hbs'),
+  parserOptions: {
+    ecmaVersion: 2022,
+    sourceType: 'module',
+  },
+});
+
+hbsRuleTester.run('template-no-valueless-arguments', rule, {
+  valid: validHbs,
+  invalid: invalidHbs,
+});