template-no-block-params-for-html-elements.js

/** @type {import('eslint').Rule.RuleModule} */

// Mirror upstream ember-template-lint's inverse-of-isAngleBracketComponent logic.
// A tag is treated as an HTML element only when it:
//   - does NOT contain ':' (named blocks like <:slot>)
//   - does NOT contain '.' (path/namespaced invocations like <foo.bar>)
//   - does NOT start with '@' (argument invocations like <@foo>)
//   - has NO uppercase letters (component invocations like <MyThing>)
//   - does NOT contain '-' (HTML custom elements like <my-element>)
// Everything else is a component / custom-element / slot — not a plain HTML element.
function isHtmlElement(tagName) {
  if (!tagName) {
    return false;
  }
  if (tagName.startsWith('@')) {
    return false;
  }
  if (tagName.includes(':')) {
    return false;
  }
  if (tagName.includes('.')) {
    return false;
  }
  if (tagName.includes('-')) {
    return false;
  }
  if (tagName !== tagName.toLowerCase()) {
    return false;
  }
  return true;
}

module.exports = {
  meta: {
    type: 'problem',
    docs: {
      description: 'disallow block params on HTML elements',
      category: 'Best Practices',

      url: 'https://github.com/ember-cli/eslint-plugin-ember/tree/master/docs/rules/template-no-block-params-for-html-elements.md',
    },
    fixable: null,
    schema: [],
    messages: {
      noBlockParamsForHtmlElements:
        'Block params can only be used with components, not HTML elements.',
    },
  },

  create(context) {
    const sourceCode = context.sourceCode;

    return {
      GlimmerElementNode(node) {
        // Check if this is an HTML element (not a component / custom element / slot)
        if (!isHtmlElement(node.tag)) {
          return;
        }

        // If the tag name is a variable in scope, it's being used as a component, not an HTML element
        const scope = sourceCode.getScope(node.parent);
        const isVariable = scope.references.some((ref) => ref.identifier === node.parts[0]);
        if (isVariable) {
          return;
        }

        // Check for block params
        if (node.blockParams && node.blockParams.length > 0) {
          context.report({
            node,
            messageId: 'noBlockParamsForHtmlElements',
          });
        }
      },
    };
  },
};