ember-template-imports

ember-template-imports

This addon provides the build tooling required to support Ember's next-gen component authoring format:

import { on } from '@ember/modifier';
import FancyButton from './fancy-button';

function greet() {
  alert("AHOY!")
}

<template>
  <p>Hello, {{@name}}!</p>
  <FancyButton @label="Say hello!" {{on "click" greet}} />
</template>

This design uses <template> to allow us to author JavaScript or TypeScript in the same file as templates, while keeping a clear separation between the template language and the JavaScript around it.

This "next-gen" format is the official future of Ember's authoring story, and is stable and usable today. (It is already being used in some of the largest Ember apps in the world!) We expect it to become the recommended way of authoring all Ember apps in the near future, once we are satisfied that we have sufficiently polished up all the corners of the implementation.

Installation and setup

Install this package and the supporting Prettier plugin:

• pnpm:

  pnpm add --save-dev ember-template-imports prettier-plugin-ember-template-tag
  

• Yarn:

  yarn add --dev ember-template-imports prettier-plugin-ember-template-tag
  

• npm:

  npm add --save-dev ember-template-imports prettier-plugin-ember-template-tag
  

Then configure the Prettier plugin following the instructions from its README. Additionally, make sure you are using at least v5.8.0 of ember-template-lint and v11.6.0 of eslint-plugin-ember, so your linting tools will work correctly.

Additionally, if you are using TypeScript, you will also want to set up Glint, following its setup instructions. (Make sure you include @glint/environment-ember-template-imports!)

Compatibility

• Ember.js v3.27 or above
• Ember CLI v3.27 or above
• ember-cli-htmlbars 6.3.0 or above
• Node.js v12 or above

Editor Integrations

To get syntax highlighting inside embedded templates and support for the GJS file extension, you may need to configure your editor.

Visual Studio Code

The Ember.js extension pack bundles everything you need to get started.

Neovim

Example Neovim Config with support for good highlighting of embedded templates in JS and TS, using:

• https://github.com/nvim-treesitter/nvim-treesitter
• https://github.com/alexlafroscia/tree-sitter-glimmer

Additionally, when using the eslint-lsp, you'll need to tell ESLint to activate when javascript.glimmer and typescript.glimmer files are loaded. Example.

Configure ESLint for gjs + gts and fix-on-save

local lsp = require('lspconfig')
  
-- ✂️ 

local eslint = lsp['eslint']
  
eslint.setup({
  filetypes = { 
    "javascript", "typescript", 
    "typescript.glimmer", "javascript.glimmer", 
    "json", 
    "markdown" 
  },
  on_attach = function(client, bufnr)
    vim.api.nvim_create_autocmd("BufWritePre", {
      buffer = bufnr,
      command = "EslintFixAll",
    })
  end,
})

Other editors

For other editors, you may be able to get support using one of these other syntax definitions:

• TextMate
• TreeSitter

Using Template Tags and .gjs/.gts Files

The new <template> tag format is available in .gjs and .gts files. These file extensions represent a new file format "GlimmerJS" and "GlimmerTS", which are supersets of standard JavaScript and TypeScript respectively. In this syntax, templates are defined in JavaScript files directly.

This example defines a template-only component, which is the default export of hello.gjs:

// components/hello.gjs
<template>
  <span>Hello, {{@name}}!</span>
</template>

You would be able to use this component in another component like so:

// components/hello-world.gjs
import Hello from './hello';

<template>
  <Hello @name="world" />
</template>

You can also export the component explicitly:

// components/hello.gjs
export default <template>
  <span>Hello, {{@name}}!</span>
</template>;

Omitting the export default is just syntactic sugar. In addition, you can define template-only components and assign them to variables, allowing you to export components with named exports:

export const First = <template>First</template>;

export const Second = <template>Second</template>;

export const Third = <template>Third</template>;

This also allows you to create components that are only used locally, in the same file:

const Option = <template>
  <option selected={{@selected}} value={{@value}}>
    {{or @title @value}}
  </option>
</template>;

export const CustomSelect = <template>
  <select>
    {{#each @options as |opt|}}
      <Option
        @value={{opt.value}}
        @selected={{eq opt @selectedOption}}
      />
    {{/each}}
  </select>
</template>;

Helpers and modifiers can also be defined in the same file as your components, making them very flexible:

import { modifier } from 'ember-modifier';

const plusOne = (num) => num + 1;

const setScrollPosition = modifier((element, [position]) => {
  element.scrollTop = position
});

<template>
  <div class="scroll-container" {{setScrollPosition @scrollPos}}>
    {{#each @items as |item index|}}
      Item #{{plusOne index}}: {{item}}
    {{/each}}
  </div>
</template>

Finally, to associate a template with a class-based component, you can use the template syntax directly in the class body:

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { on } from '@ember/modifier';

// components/hello.gjs
export default class Hello extends Component {
  @tracked count = 0;

  increment = () => {
    this.count += 1;
  };

  decrement = () => {
    this.count -= 1;
  };

  <template>
    <button {{on "click" this.increment}}>+</button>
    Count: {{this.count}}
    <button {{on "click" this.decrement}}>&minus;</button>
  </template>
}

Template tag components can also be used for writing tests. In fact, this aligned syntax between app code and test code is one of the big advantages of the new authoring format.

Just like in app code, the template tag has access to the outer scope. This means you can reference variables directly in your tests:

// tests/integration/components/hello-test.gjs
import Hello from 'example-app/components/hello';
import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';
import { render } from '@ember/test-helpers';

module('Integration | Component | hello', function (hooks) {
  setupRenderingTest(hooks);

  test('renders name argument', async function (assert) {
    const name = 'world';
    await render(<template><Hello @name={{name}} /></template>);
    assert.dom('[data-test-id="some-selector"]').hasText(name);
  });
});

Sourcemap Generation

This can be useful for development and test purposes, it should be disabled for production

// ember-cli-build.js
module.exports = function (defaults) {
  let app = new EmberAddon(defaults, {
    'ember-template-imports': {
      inline_source_map: true
    }
  });

Reference: built-in helpers, modifiers, components

As implemented as part of the Strict Mode Templates RFC, the built in helpers, modifiers and components are available for import:

• array (import { array } from '@ember/helper';)
• concat (import { concat } from '@ember/helper';)
• fn (import { fn } from '@ember/helper';)
• get (import { get } from '@ember/helper';)
• hash (import { hash } from '@ember/helper';)
• unique-id (import { uniqueId } from '@ember/helper';, needs Ember v5.2+)
• on (import { on } from '@ember/modifier';)
• Input (import { Input } from '@ember/component';)
• LinkTo (import { LinkTo } from '@ember/routing';)
• Textarea (import { Textarea } from '@ember/component';)

Reference: import external helpers, modifiers, components

You can import non .gjs/.gts helpers, modifiers and components from apps/addons you may already be using when migrating your own components. To determine the import path:

1. Check the app
   1. If found, import that
   2. If not found,
      1. Check all addon's app folders
         1. When found, look in the matching file to see what the re-export is -- this is what you can use in your app
      2. Check all v2-addon's ember-addon#app-js configs in package.json
         1. When found, look in the matching file to see what the re-export is -- this is what you can use in

For example:

import BasicDropdown from 'ember-basic-dropdown/components/basic-dropdown';

<template>
  <BasicDropdown>
   <!-- Your component implementation here -->
  </BasicDropdown>
</template>

History

Like Glimmer components, the primitive APIs for supporting imports were built before we decided on a final format for their high level usage in RFC 0779. There were a number of different ideas for how we can integrate imports with templates, and the idea behind this addon was that it could be a test bed for them all. This allowed us to share common tooling between solutions, and work together as a community as we explored the design space.

The main alternative explored in a previous version was template literals, similar to the existing hbs helper in tests:

import { hbs } from 'ember-template-imports';
import MyComponent from './my-component';

export default hbs`
  <MyComponent/>
`;

For the previous version of this addon, see this repository. And huge thanks to @patricklx for his contributions here!

As of RFC 0779, we decided on <template> over hbs; see the RFC for the full rationale. The hbs format is still technically supported by this repo for transition purposes for the early adopters who helped us get here, but will be removed at some point in the near future! hbs has been removed -- if you rely on this feature, please use ember-template-imports @ < v4, until migrated to <template>

Contributing

See the Contributing guide for details.

License

This project is licensed under the MIT License.