👀 Lookbook 👀

A native development UI for ViewComponent

Installing • Previews • Pages • Configuration

--- **Lookbook gives [ViewComponent](http://viewcomponent.org/)-based projects a _ready-to-go_ development UI for navigating, inspecting and interacting with component previews.** It uses (and extends) the native [ViewComponent preview functionality](https://viewcomponent.org/guide/previews.html), so you don't need to learn a new DSL or create any extra files to get up and running. Lookbook uses [RDoc/Yard-style comment tags](#annotating-preview-files) to extend the capabilities of ViewComponent's previews whilst maintaining compatability with the standard preview class format, so you can add or remove Lookbook at any time without having to rework your code. ![Lookbook UI](.github/assets/lookbook_screenshot.png) ### Features - Tree-style navigation menu with live search/filter - Resizable preview window for responsive testing - Highlighted preview source code and HTML output - Auto-updating UI when component or preview files are updated _(Rails v6.0+ only)_ - Use comment tag annotations for granular customisation of the preview experience - Fully compatible with standard the ViewComponent preview system - In-browser live-editable preview parameters (similar to basic Storybook Controls/Knobs) - [**Experimental**] Markdown-powerered documentation pages with embeddable previews ## Lookbook demo If you want to have a quick play with Lookbook, the easiest way is to [give the demo app](https://github.com/allmarkedup/lookbook-demo) a spin. It's a basic Rails/ViewComponent app with a few test components included to tinker with. **Online demo: https://lookbook-demo-app.herokuapp.com/lookbook** If you'd rather dig in a bit more and run the demo app locally, the [demo repo](https://github.com/allmarkedup/lookbook-demo) contains instructions on how to get it up and running. ## Installing ### 1. Add as a dependency Add Lookbook to your `Gemfile` somewhere **after** the ViewComponent gem. For example: ```ruby gem "view_component", require: "view_component/engine" gem "lookbook" ``` ### 2. Mount the Lookbook engine You then need to mount the Lookbook engine (at a path of your choosing) in your `routes.rb` file: ```ruby Rails.application.routes.draw do if Rails.env.development? mount Lookbook::Engine, at: "/lookbook" end end ``` The `at` property determines the root URL that the Lookbook UI will be served at. Then you can start your app as normal and navigate to `http://localhost:3000/lookbook` (or whatever mount path you specified) to view your component previews in the Lookbook UI. #### Mounting in Production If you would like to expose the Lookbook UI in production as well as in development 1. Remove the `if Rails.env.development?` condition from around the mount statement in `routes.rb` 2. Add `config.view_component.show_previews = true` to `config/environments/production.rb`

Previews

You don't need to do anything special to see your ViewComponent previews and examples in Lookbook - just create them as normal and they'll automatically appear in the Lookbook UI. Preview templates, custom layouts and even bespoke [preview controllers](https://viewcomponent.org/guide/previews.html#configuring-preview-controller) should all work as you would expect. > If you are new to ViewComponent development, checkout the ViewComponent [documentation](https://viewcomponent.org/guide/) on how to get started developing your components and [creating previews](https://viewcomponent.org/guide/previews.html). ### Annotating preview files Lookbook parses [Yard-style comment tags](https://rubydoc.info/gems/yard/file/docs/Tags.md) in your preview classes to customise and extend the standard ViewComponent preview experience: ```ruby # @label Basic Button # @display bg_color "#fff" class ButtonComponentPreview < ViewComponent::Preview # Primary button # --------------- # This is the button style you should use for most things. # # @label Primary def default render ButtonComponent.new do "Click me" end end # Button with icon # ---------------- # This example uses dynamic preview parameters # which can be edited live in the Lookbook UI # # @param text # @param icon select [heart, cog, alert] def icon(text: "Spread the love", icon: "heart") render ButtonComponent.new(icon: icon) do text end end # Inverted button # --------------- # For light-on-dark screens # # @display bg_color "#000" def secondary render ButtonComponent.new(style: :inverted) do "Click me" end end # Unicorn button # --------------- # This button style is still a **work in progress**. # # @hidden def secondary render ButtonComponent.new do "Click me" end end # @!group More examples def short_text render ButtonComponent.new do "Go" end end def long_text render ButtonComponent.new do "Click here to do this thing because it's the best way to do it" end end def emoji_text render ButtonComponent.new do "👀📗" end end # @!endgroup end ``` **Tags** are just strings identified by their `@` prefix - for example `@hidden`. Tags are always placed in a comment above the relevant preview class or example method. The following Lookbook-specific tags are available for use: * [`@label`](#label-tag) * [`@display`](#display-tag) * [`@!group ... @!endgroup`](#group-tag) * [`@hidden`](#hidden-tag) * [`@param`](#param-tag)

🏷 @label

Used to replace the auto-generated navigation label for the item with ``. ```ruby @label ``` > Available for preview classes & example methods. ```ruby # @label Preview Label class FooComponentPreview < ViewComponent::Preview # @label Example Label def default end end ```

🏷 @display

The `@display` tag lets you pass custom parameters to your preview layout so that the component preview can be customised on a per-example basis. ```ruby # @display bg_color "#eee" class FooComponentPreview < ViewComponent::Preview # @display max_width 500px # @display wrapper true def default end end ``` The `@display` tag can be applied at the preview (class) or at the example (method) level, and takes the following format: ```ruby @display ``` - `` must be a valid Ruby hash key name, without quotes or spaces - `` will be parsed using the [Ruby YAML parser](https://yaml.org/YAML_for_ruby.html) to resolve the value > Note: Ruby YAML does not (generally) require quoting of string values. However in some cases it _is_ required due to the presence of [indicator characters](https://yaml.org/YAML_for_ruby.html#indicators_in_strings) (such as `#`, `:` etc) - hence why the hex color code in the example above is surrounded by quotes. It's perfectly ok to quote all string values if you prefer. These display parameters can then be accessed via the `params` hash in your preview layout using `params[:lookbook][:display][]`: ```html Preview Layout

<% if params[:lookbook][:display][:wrapper] == true %>

<%= yield %>

<% else %> <%= yield %> <% end %>

``` > By default ViewComponent will use your default application layout for displaying the rendered example. However it's often better to create a seperate layout that you can customise and use specifically for previewing your components. See the ViewComponent [preview docs](https://viewcomponent.org/guide/previews.html) for instructions on how to set that up. Any `@display` params set at the preview (class) level with be merged with those set on individual example methods. #### Global display params Global (fallback) display params can be defined via a configuration option: ```ruby # config/application.rb config.lookbook.preview_display_params = { bg_color: "#fff", max_width: "100%" } ``` Globally defined display params will be available to all previews. Any preview or example-level `@display` values with the same name will take precedence and override a globally-set one.

🔖 `@!group ... @!endgroup`

For smaller components, it can often make sense to render a set of preview examples in a single window, rather than representing them as individual items in the navigation which can start to look a bit cluttered. You can group a set of examples by wrapping them in `@!group ` / `@!endgroup` tags within your preview file: ```ruby class HeaderComponentPreview < ViewComponent::Preview def standard render Elements::HeaderComponent.new do "Standard header" end end # @!group Sizes def small render Elements::HeaderComponent.new(size: 12) do "Small header" end end def medium render Elements::HeaderComponent.new(size: 16) do "Small header" end end def big render Elements::HeaderComponent.new(size: 24) do "Small header" end end # @!endgroup end ``` The example above would display the `Sizes` examples grouped together on a single page, rather than as indiviual items in the navigation:

You can have as many groups as you like within a single preview class, but each example can only belong to one group.

🏷 `@hidden`

Used to temporarily exclude an item from the Lookbook navigation. The item will still be accessible via it's URL. Can be useful when a component (or a variant of a component) is still in development and is not ready to be shared with the wider team. > Available for both preview classes & example methods. ```ruby # @hidden class FooComponentPreview < ViewComponent::Preview # @hidden def default end end ```

@param

The `@param` tag provides the ability to specify **editable preview parameters** which can be changed in the Lookbook UI in order to customise the rendered output on the fly, much like the [Controls (knobs) addon](https://storybook.js.org/addons/@storybook/addon-controls) for Storybook. Each `@param` will have an associated form field generated for it. The values for each field will be handled as [dynamic preview params](https://viewcomponent.org/guide/previews.html#:~:text=It%E2%80%99s%20also%20possible%20to%20set%20dynamic%20values%20from%20the%20params%20by%20setting%20them%20as%20arguments%3A) when rendering the example. The `@param` tag takes the following format: ```ruby @param ``` - `` - name of the dynamic preview param - `` - input field type to generate in the UI - `` - YAML-encoded field options, used for some field types #### Input types The following **input field types** are available for use: 📝 **Text-style inputs** - Single line fields, useful for short strings of text or numbers. ```ruby @param text @param email @param number @param url @param tel ``` > The above types only differ in the validation constraints they impose on the input field. 📝 **Textarea** - Multi-line textarea field for longer-form content. ```ruby @param textarea ``` 📝 **Select box** - Dropdown select field for selecting from a list of known options. ```ruby @param select ``` `` should be a [YAML array](https://yaml.org/YAML_for_ruby.html#simple_inline_array) of options which must be formatted in the same style as the input for Rails' [`options_for_select`](https://apidock.com/rails/v6.0.0/ActionView/Helpers/FormOptionsHelper/options_for_select) helper: ```ruby # Basic options: # @param theme select [primary, secondary, danger] # With custom labels (each item itself an array of [label, value]): # @param theme select [[Primary theme, primary], [Secondary theme, secondary], [Danger theme, danger]] # With empty option (`~` in YAML) # @param theme select [~, primary, secondary, danger] ``` > **Note**: In most cases YAML does not require quoting of strings, however if you are running into issues check out the [Ruby YAML docs](https://yaml.org/YAML_for_ruby.html) for a complete syntax reference. 📝 **Toggle** - On/off switch for toggling boolean values. ```ruby @param toggle ``` #### Default values Default values are specified as part of the preview example method parameters in the usual Ruby way: ```ruby def button(content: "Click me", theme: "primary", arrow: false) # ... end ``` These will be used as the default values for the param fields. > Note that the default values are **not** evaluated at runtime, so you cannot use method calls to generate the defaults. Only static default values are supported. #### Type casting values Most dynamic param values are passed to the example method as strings, with the following exceptions: - `toggle` input - values are cast to booleans - `number` input - values are cast to integers In some cases, you may want to type cast the parameter value to something else (for example a `Symbol`) before using it when initializing the component. To help with this, a `type` option can be specified in the `@param` definition to automatically cast the dynamic value to a different type: ```ruby # @param [] ``` In the example below, the value of the `theme` param (by default a string) will be automatically cast to a Symbol, ready for use in instantiating the component. ```ruby # @param theme [Symbol] select [primary, secondary, danger] def default(theme: :primary) render Elements::ButtonComponent.new(theme: theme) do "Click me" end end ``` The supported types to cast to are: - `String` - *default for all except `toggle` inputs* - `Boolean` - *default for `toggle` inputs* - `Symbol` - `Date` - `DateTime` - `Integer` - `Float` The following structured types are also available but should be considered **experimental** - you may run into bugs! - `Hash` - *value string converted to Hash using the Ruby YAML parser* - `Array` - *value string converted to Array using the Ruby YAML parser* #### Full example: ```ruby class ButtonComponentPreview < ViewComponent::Preview # The params defined below will be editable in the UI: # # @param content text # @param theme select [primary, secondary, danger] # @param arrow toggle def default(content: "Click me", theme: "primary", arrow: true) render Elements::ButtonComponent.new(theme: theme, arrow: arrow) do content end end end ```

### Adding notes All comment text other than tags will be treated as markdown and rendered in the **Notes** panel for that example in the Lookbook UI. ```ruby # @hidden class ProfileCardComponentPreview < ViewComponent::Preview # Profile Card # ------------ # Use the default profile card component whenever you need to represent a user. def default end end ``` ---

🚧 Documentation Pages [experimental]

If you need to add more long-form documentation to live alongside your component previews you can do so using Lookbook's markdown-powered `pages` system. > ⚠️ This feature is currently flagged as an **experimental** feature which requires [feature opt-in](#experimental-features) to use. Its API and implementation may change before it is released. > > To enable support for pages in your project, add `config.lookbook.experimental_features = [:pages]` into your application configuration file. ### Pages demo For an example of some pages in Lookbook, check out the [example pages](https://lookbook-demo-app.herokuapp.com/lookbook) in the Lookbook demo app and the associated [page files](https://github.com/allmarkedup/lookbook-demo/tree/main/test/components/docs) in the demo repo. ### Usage By default, pages should be placed in the `test/components/docs` directory (although this can be customised) and can be nested in directories as deeply as required. Pages must have either a `.html.erb` or a `.md.erb` file extension. All pages are rendered as ERB templates but `.md.erb` files will also additionally be run through a markdown parser. Pages can optionally make use of a **YAML frontmatter block** to customise the behaviour and content of the page itself. An example page might look like this: ```markdown --- title: An example page label: Nice example --- This is an example page. If it has a `.md.erb` file extension its contents will be run through a Markdown parser/renderer before display. Fenced code blocks are fully supported and will be highlighted appropriately. ERB can be used in here. The template will be rendered **before** being parsed as Markdown. You can can access data about the page using the `@page` variable. The title of this page is "<%= @page.title %>". ``` ### YAML Frontmatter Pages can use an optional YAML frontmatter block to configure the behaviour of the page and to provide custom data, if required. The following page options can be customised via frontmatter: * `id` - a custom page ID that can be used for linking to it from other pages * `label` - The name of the page that will be displayed in the navigation (auto-generated from the file name if not set) * `title` - The main page title displayed on the page (defaults to the label value if not set). * `hidden` - If `false` the page will not appear in the navigation but will still be accessible at it's URL (useful for pages that are still in development) [default: `true`] * `landing` - Set to `true` to use the page as the Lookbook landing page [default: `false`] * `header` - Set to `false` to hide the page header containing the page title [default: `true`] * `footer` - Set to `false` to hide the page footer containing the previous/next page links [default: `true`] * `data` - Optional hash of custom data to make available for use in the page - see info on [page variables](#page-variables) below. [default: `{}`] #### Frontmatter defaults You can set global default values for page options in the application configuration: ```ruby # config/application.rb config.lookbook.page_options = { footer: false, data: { brand_colors: { red: #ff0000 } } } ``` These will be merged with any page-level frontmatter data. Options set in the frontmatter will override those set at the global level (apart from `data`, which will be deep-merged with the any globally defined data). ### Page variables All pages have the following variables available for use in the page template: * `@page` - The current page object * `@next_page` - The next page object (if available) * `@previous_page` - The previous page object (if available) * `@pages` - Collection of all pages Page objects have access to frontmatter variables: ```ruby The page title is <%= @page.title %> Our brand color hex value is <%= @page.data[:brand_colors][:red] %> ``` ### Ordering pages and directories If you want to enforce a specific order for pages and directories in the Lookbook navigation you can prefix the file/directory basename with an 'order number' integer value followed by an underscore or hyphen. For example: `01_example_page.md.erb` will be displayed first in the navigation (`01`) within the directory it is in. The integer value will be parsed out from the filename so that it doesn't appear in navigation labels or URLs, and the value itself will be used as a 'position' number when sorting the navigation items. For example, an ordered directory of pages might look like: ``` test/components/docs/ ├── 01_overview.md.erb ├── 02_implementation_notes/ │ ├── 01_slots.md.erb │ └── 02_html_attributes.md.erb └── 03_helpful_examples/ ├── 01_basic_components.md.erb └── 02_complex_components.md.erb ``` Without the number prefixes on the file names the pages may not have appeared in the navigation in the desired order. ### Linking to other pages You can get the path to a page using the `page_path` helper. This accepts a page `id` (as a `Symbol`) or a page object: ```markdown Visit the [about page](<%= page_path :about %>) Go to the [next page](<%= page_path @next_page %>) ``` Page ids can be set in the YAML frontmatter block for that page: ``` --- id: about --- This is the about page. ``` ### Embedding previews You can embed preview examples from your project directly into the documentation pages using the `embed` helper, which renders an iframe with the rendered preview in it at any point in your document. The output looks like this:

To specify which preview example to render, the helper accepts a preview class and a method name (as a symbol), like this: ```erb <%= embed Elements:ButtonComponentPreview, :default %> ``` #### Preview params If you have configured your examples to accept preview params (see the [`@param`](#param-tag) docs), then you can supply values for those params when rendering the embedded preview: ```erb <%= embed Elements:ButtonComponentPreview, :default, params: { icon: "plus", text: "Add new" } %> ``` ### Displaying code You can use language-scoped [fenced code blocks](https://www.markdownguide.org/extended-syntax/#fenced-code-blocks) in the markdown file to render nicely highlighted code examples. However, if you are not using Markdown, or need a little more control, you can use the `code` helper instead: ```erb <%= code do %> # code goes here <% end %> ``` The default language is `ruby`. To highlight a different language you need to specify it's name as an argument: ```erb <%= code :html do %> <% end %> ``` > Lookbook uses [Rouge](https://github.com/rouge-ruby/rouge) for syntax highlighting. You can find a [full list of supported languages here](https://github.com/rouge-ruby/rouge/blob/master/docs/Languages.md). --- ### Pages configuration These options can be set in your application configuration files to customise the pages behaviour. #### `page_paths` An array of directories to look for pages in. Default: `["test/previews/docs"]` ```ruby config.lookbook.page_paths = ["path/to/my/pages"] ``` #### `page_route` The URL segment used to prefix page routes. Default: `pages` ```ruby config.lookbook.page_route = `docs` ```

General Configuration

Lookbook will use the ViewComponent [configuration](https://viewcomponent.org/api.html#configuration) for your project to find and render your previews so you generally you won't need to configure much else separately. However the following Lookbook-specific configuration options are also available: ### UI auto-refresh > ⚠️ UI auto-refresh is only supported in Rails v6.0+ Disable/enable the auto-updating of the Lookbook UI when files change. Enabled by default. ```ruby config.lookbook.auto_refresh = false # default is true ``` By default Lookbook will listen for changes in any [preview directories](https://viewcomponent.org/api.html#preview_paths) as well as in the [components directory](config.view_component.preview_paths) itself. If you wish to add additional paths to listen for changes in, you can use the `listen_paths` option: ```ruby config.lookbook.listen_paths << Rails.root.join('app/other/directory') ``` ### Custom favicon If you want to change the favicon used by the Lookbook UI, you can provide a path to your own (or a data-uri string) using the `ui_favicon` option: ```ruby config.lookbook.ui_favicon = "/path/to/my/favicon.png" ``` > To disable the favicon entirely, set the value to `false`. ### Project name Specify a project name to display in the top left of the UI (instead of the default "Lookbook"): ```ruby config.lookbook.project_name = "My Project" ``` > If you don't want to display a project name at all, set the value to `false`.

Experimental features opt-in

Some features may occasionally be released behind a 'experimental' feature flag while they are being tested and refined, to allow people to try them out and provide feedback. > ⚠️ **Please note:** Experimental features should be considered to be **subject to extensive change** and breaking changes to them may be made within point releases - these features are **not** considered to be covered by [semver](https://semver.org/) whilst flagged as 'experimental'. ⚠️ #### Opting into specific features (recommended) To opt into individual experimental features, include the name of the feature in the `experimental_features` config option: ```ruby config.lookbook.experimental_features = ["feature_name"] ``` The current experimental features that can be opted into are: - `pages`: Markdown-powered documentation pages with embeddable previews #### Opting into all experimental features (not recommended!) If you want to live life on the bleeding-edge you can opt-in to all current **and future** experimental features (usual caveats apply): ```ruby config.lookbook.experimental_features = true ``` ## Keyboard shortcuts Lookbook provides a few keyboard shortcuts to help you quickly move around the UI. - `f` - move focus to the nav filter box - `Esc` [when focus is in nav filter box] - Clear contents if text is present, or return focus to the UI if the box is already empty - `s` - Switch to Source tab in the drawer - `n` - Switch to Notes tab in the drawer - `v` - Switch to the rendered preview - `o` - Switch to the code preview - `r` - Refresh the preview (useful if using something like Faker to generate randomised data for the preview) - `w` - Open the standalone rendered preview in a new window ## Contributing Lookbook is very much a small hobby/side project at the moment. I'd love to hear from anyone who is interested in contributing but I'm terrible at replying to emails or messages, so don't be surprised if I take forever to get back to you. It's not personal 😜 ### Developing on a local version of Lookbook The quickest way to get a development version of Lookbook up and running is to use the [lookbook-demo](https://github.com/allmarkedup/lookbook-demo) app and link it to a local version of the Lookbook gem: #### Initial setup: 1. Clone this repository somewhere on your machine - `git clone git@github.com:allmarkedup/lookbook.git` 2. Also pull down the [lookbook-demo](https://github.com/allmarkedup/lookbook-demo) repository to your machine 3. In the `Gemfile` of the `lookbook-demo` repository, replace `gem "lookbook", '>= 0.1', git: "https://github.com/allmarkedup/lookbook", branch: "main"` with `gem "lookbook", path: "../path/to/lookbook"` (use the path to your local copy of lookbook) 4. Install dependencies - from the root of the parent project run `bundle install` #### Starting development 1. From within the `lookbook` root directory run the comand `npm run dev` (this will make sure the CSS/JS is recompiled if/when you make changes to the UI) 2. From within the `lookbook-demo` root directory run `npm run start` - this will start a server and build the demo assets Point your browser to http://localhost:3000/lookbook to see the UI. You can then make and test changes to the Lookbook code in your local copy of lookbook repo. PRs are welcome if you add anything useful :-) > Note that changes to files in the Lookbook `lib/` directory will require a server restart in order to have them applied. #### Tests You can run the tests from within the `lookbook` root directory with the `rake test` command. ## License The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).