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guides/release/polaris/strict-mode-components.md

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+ember-template-imports
+==============================================================================
+
+This addon provides the build tooling required to support Ember's next-gen component authoring format:
+
+```js
+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][rfc-0779] 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.
+
+[rfc-0779]: https://rfcs.emberjs.com/id/0779-first-class-component-templates
+
+
+## Installation and setup
+
+Install this package and [the supporting Prettier plugin][prettier-plugin]:
+
+[prettier-plugin]: https://github.com/gitKrystan/prettier-plugin-ember-template-tag
+
+- pnpm:
+
+  ```sh
+  pnpm add --save-dev ember-template-imports prettier-plugin-ember-template-tag
+  ```
+
+- Yarn:
+
+  ```sh
+  yarn add --dev ember-template-imports prettier-plugin-ember-template-tag
+  ```
+
+- npm:
+
+  ```sh
+  npm add --save-dev ember-template-imports prettier-plugin-ember-template-tag
+  ```
+
+Then configure the Prettier plugin following [the instructions from its
+README][prettier-plugin]. Additionally, make sure you are using at least v5.8.0
+of [ember-template-lint][etl] and v11.6.0 of [eslint-plugin-ember][epe], so your
+linting tools will work correctly.
+
+[etl]: https://github.com/ember-template-lint/ember-template-lint
+[epe]: https://github.com/ember-cli/eslint-plugin-ember
+
+Additionally, if you are using TypeScript, you will also want to set up
+[Glint][glint], following [its setup instructions][glint-setup]. (Make sure you
+include `@glint/environment-ember-template-imports`!)
+
+[glint]: https://typed-ember.gitbook.io/glint
+[glint-setup]: https://typed-ember.gitbook.io/glint/environments/ember/installation
+
+
+## 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](https://marketplace.visualstudio.com/items?itemName=EmberTooling.emberjs) bundles everything you need to get started.
+
+
+### Neovim
+
+[Example Neovim Config](https://github.com/NullVoxPopuli/dotfiles/blob/main/home/.config/nvim/lua/plugins/syntax.lua#L52) 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](https://github.com/NullVoxPopuli/dotfiles/blob/main/home/.config/nvim/lua/plugin-config/lsp/init.lua#L147).
+
+<details><summary>Configure ESLint for gjs + gts and fix-on-save</summary>
+
+```lua
+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,
+})
+```
+
+</details>
+
+
+### Other editors
+
+For other editors, you may be able to get support using one of these other syntax definitions:
+
+- [TextMate](https://github.com/IgnaceMaes/glimmer-textmate-grammar)
+- [TreeSitter](https://github.com/alexlafroscia/tree-sitter-glimmer)
+
+
+## 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`:
+
+```js
+// components/hello.gjs
+<template>
+  <span>Hello, {{@name}}!</span>
+</template>
+```
+
+You would be able to use this component in another component like so:
+
+```js
+// components/hello-world.gjs
+import Hello from './hello';
+
+<template>
+  <Hello @name="world" />
+</template>
+```
+
+You can also export the component explicitly:
+
+```js
+// 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:
+
+```js
+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:
+
+```js
+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:
+
+```js
+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:
+
+```js
+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:
+
+```js
+// 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);
+  });
+});
+
+```
+
+## Reference: built-in helpers, modifiers, components
+
+As implemented as part of the [Strict Mode Templates RFC][rfc-496], 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';`)
+* `on` (`import { on } from '@ember/modifier';`)
+* `Input` (`import { Input } from '@ember/component';`)
+* `LinkTo` (`import { LinkTo } from '@ember/routing';`)
+* `Textarea` (`import { Textarea } from '@ember/component';`)
+
+[rfc-496]: https://github.com/emberjs/rfcs/pull/496
+
+
+## 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][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:
+
+```js
+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][first-repo]. And
+huge thanks to @patricklx for his contributions here!
+
+[first-repo]: https://github.com/patricklx/ember-template-imports
+
+As of [RFC 0779][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>`