Merge pull request #2457 from NullVoxPopuli/nvp/template-lint-extract-rule-template-no-bare-yield

Extract rule: template-no-bare-yield

Author: NullVoxPopuli

README.md

@@ -204,6 +204,7 @@ rules in templates can be disabled with eslint directives with mustache or html
 | [template-no-action-on-submit-button](docs/rules/template-no-action-on-submit-button.md)                     | disallow action attribute on submit buttons                                  |    |    |    |
 | [template-no-arguments-for-html-elements](docs/rules/template-no-arguments-for-html-elements.md)             | disallow @arguments on HTML elements                                         |    |    |    |
 | [template-no-array-prototype-extensions](docs/rules/template-no-array-prototype-extensions.md)               | disallow usage of Ember Array prototype extensions                           |    |    |    |
+| [template-no-bare-yield](docs/rules/template-no-bare-yield.md)                                               | disallow templates whose only meaningful content is a bare {{yield}}         |    |    |    |
 | [template-no-block-params-for-html-elements](docs/rules/template-no-block-params-for-html-elements.md)       | disallow block params on HTML elements                                       |    |    |    |
 | [template-no-capital-arguments](docs/rules/template-no-capital-arguments.md)                                 | disallow capital arguments (use lowercase @arg instead of @Arg)              |    |    |    |
 | [template-no-chained-this](docs/rules/template-no-chained-this.md)                                           | disallow redundant `this.this` in templates                                  |    | 🔧 |    |

docs/rules/template-no-bare-yield.md

@@ -0,0 +1,31 @@
+# ember/template-no-bare-yield
+
+<!-- end auto-generated rule header -->
+
+Disallow `{{yield}}` without parameters outside of contextual components.
+
+## Rule Details
+
+This rule enforces passing parameters to `{{yield}}` to make component APIs more explicit.
+
+## Examples
+
+Examples of **incorrect** code for this rule:
+
+```gjs
+<template>
+  {{yield}}
+</template>
+```
+
+Examples of **correct** code for this rule:
+
+```gjs
+<template>
+  {{yield (Object greeting="hello there")}}
+</template>
+
+<template>
+  {{yield @model}}
+</template>
+```

lib/rules/template-no-bare-yield.js

@@ -0,0 +1,64 @@
+function isEmptyNode(node) {
+  return (
+    node.type === 'GlimmerMustacheCommentStatement' ||
+    node.type === 'GlimmerCommentStatement' ||
+    (node.type === 'GlimmerTextNode' && !node.chars.trim())
+  );
+}
+
+function isBareYield(node) {
+  return (
+    node.type === 'GlimmerMustacheStatement' &&
+    node.path.original === 'yield' &&
+    (!node.params || node.params.length === 0)
+  );
+}
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+  meta: {
+    type: 'problem',
+    docs: {
+      description: 'disallow templates whose only meaningful content is a bare {{yield}}',
+      category: 'Best Practices',
+      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-bare-yield.md',
+      templateMode: 'both',
+    },
+    schema: [],
+    messages: {
+      noBareYield: '{{yieldCall}}-only templates are not allowed.',
+    },
+    originallyFrom: {
+      name: 'ember-template-lint',
+      rule: 'lib/rules/no-yield-only.js',
+      docs: 'docs/rule/no-yield-only.md',
+      tests: 'test/unit/rules/no-yield-only-test.js',
+    },
+  },
+
+  create(context) {
+    return {
+      GlimmerTemplate(node) {
+        // In GJS/GTS mode the content lives inside a GlimmerElementNode wrapper
+        // with tag="template"; in HBS mode the body is the content directly.
+        let body = node.body;
+        if (
+          body.length === 1 &&
+          body[0].type === 'GlimmerElementNode' &&
+          body[0].tag === 'template'
+        ) {
+          body = body[0].children;
+        }
+
+        const nonEmptyNodes = body.filter((n) => !isEmptyNode(n));
+        if (nonEmptyNodes.length === 1 && isBareYield(nonEmptyNodes[0])) {
+          context.report({
+            node: nonEmptyNodes[0],
+            messageId: 'noBareYield',
+            data: { yieldCall: '{{yield}}' },
+          });
+        }
+      },
+    };
+  },
+};

tests/lib/rules/template-no-bare-yield.js

@@ -0,0 +1,82 @@
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const rule = require('../../../lib/rules/template-no-bare-yield');
+const RuleTester = require('eslint').RuleTester;
+
+const ruleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+ruleTester.run('template-no-bare-yield', rule, {
+  valid: [
+    // yield with params is fine
+    '<template>{{yield this}}</template>',
+    '<template>{{yield @model}}</template>',
+    '<template>{{yield (hash someProp=someValue)}}</template>',
+    // yield is not the only content
+    '<template>{{yield}}<div>Content</div></template>',
+    '<template><div>Content</div>{{yield}}</template>',
+    // no yield at all
+    '<template><div>Content</div></template>',
+  ],
+  invalid: [
+    {
+      code: '<template>{{yield}}</template>',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+    {
+      // whitespace around yield doesn't count as other content
+      code: '<template>  {{yield}}  </template>',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+    {
+      // comments don't count as other content
+      code: '<template>{{! a comment }}{{yield}}</template>',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+  ],
+});
+
+const hbsRuleTester = new RuleTester({
+  parser: require.resolve('ember-eslint-parser/hbs'),
+  parserOptions: { ecmaVersion: 2022, sourceType: 'module' },
+});
+
+hbsRuleTester.run('template-no-bare-yield', rule, {
+  valid: [
+    '{{yield (hash someProp=someValue)}}',
+    '{{yield this}}',
+    // yield with other content
+    '{{yield}}<div>Content</div>',
+  ],
+  invalid: [
+    {
+      code: '{{yield}}',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+    {
+      // whitespace around yield doesn't count as other content
+      code: '     {{yield}}',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+    {
+      code: '\n  {{yield}}\n     ',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+    {
+      // comments don't count as other content
+      code: '\n{{! some comment }}  {{yield}}\n     ',
+      output: null,
+      errors: [{ messageId: 'noBareYield' }],
+    },
+  ],
+});