@scullyio/scully-plugin-flash-prevention

The `scully-plugin-flash-prevention` is a postRenderer that helps you hide any flashes that your app may be experiencing once you add Scully to your project.

Usage no npm install needed!

<script type="module">
  import scullyioScullyPluginFlashPrevention from 'https://cdn.skypack.dev/@scullyio/scully-plugin-flash-prevention';
</script>

README

ScullyPluginFlashPrevention

The scully-plugin-flash-prevention is a postRenderer that helps you hide any flashes that your app may be experiencing once you add Scully to your project.

After adding Scully, your app will appear instantly because the pre-rendered HTML and CSS is immediately available. After appearing instantly, the JavaScript and CSS files will download and then your Angular app will bootstrap (init). When it bootstraps, the pre-rendered version may disappear for a moment, and then once the app is ready, the view will re-appear. This disappearing-then-appearing is very normal for apps that are pre-rendered on a server. This project is to prevent that.

This project shows the pre-rendered copy of your app until your app is fully render and the flash is over. It then shows your app and deletes the copy.

How it works

Before this plugin, you app would pre-render and then save to file, like this:

<app-root _nghost-abc="" ng-version="9.0.1" class="my-class">
  // The entire content of your app here
</app-root>

After this plugin, you will see the following in your pre-rendered template:

<app-root class="my-class"></app-root>
<app-root-scully _nghost-abc="" ng-version="9.0.1" class="my-class">
  // The entire content of your app here
</app-root-scully>

This app-root-scully will be the pre-rendered copy of your app. Prior to your app being rendered fully, app-root will be hidden and app-root-scully will be displayed. Once your app has fully bootstrapped, app-root-scully will be hidden and then 100ms later removed from the DOM. The mechanism that shows and hides these two is CSS. There is some CSS added during the Scully build that looks like the following:

body:not(.loaded) app-root {
  display: none;
}
body.loaded app-root-scully {
  display: inherit;
}

Once the app has been fully loaded, the loaded class is added to the <body> tag.

And that's how it all works!!!

Getting Started

1. Install the plugin:

npm install -D @scullyio/scully-plugin-flash-prevention

2. Use the plugin:

Add the postRenderer to your scully.config route:

// Add this line to your imports
const { getFlashPreventionPlugin } = require('scully-plugin-flash-prevention');

// Add the following to specific routes via the `postRenderers` property
exports.config = {
  '/users/:userId': {
      ...
      postRenderers : [getFlashPreventionPlugin({appRootSelector: 'custom-app-root'})],
      ...
  }
  ...
}

You only need to pass the {appRootSelector: 'custom-app-root'} if your app has a selector other than app-root. It is defaulted to app-root.

Update app.module to include alwaysMonitor in the ScullyLibModule.forRoot call.

ScullyLibModule.forRoot({
  useTransferState: true,
  alwaysMonitor: true,  <-- Add this line to your `app.module.ts`
});

Apply any styles from app-root to app-root-scully as well. Any styles that are in your app.component.(css|scss|less) need to be applied to the copy of your app that was made. This means that you need to possibly move any styles that apply to the app-root specifically, and put them in a location where you can also make those styles apply to app-root-scully as well. See here:

// BEFORE
app-root {
  ... some styles;
}

// AFTER
app-root,
app-root-scully {
  ... some styles;
}

That's all it takes to get set up.

Options

This plugin has a series of options you can pass it when you call getFlashPreventionPlugin(<OPTIONS HERE>). Here is a description of those options.

appRootSelector

If you AppComponent has a selector that isn't app-root, you can use this option to pass your app's custom app-root selector. If your AppComponent use the selector scully-app, you would do pass that as an arg to the getFlashPreventionPlugin function:

getFlashPreventionPlugin({appRootSelector: 'scully-app'});

appLoadedClass

Once you app loads, this plugin will add the class loaded to the body of your app. If you need to use a different class (besides the default loaded) you can pass that class name in here. If you want to use the class fploaded do the following:

getFlashPreventionPlugin({appLoadedClass: 'fploaded'});

mockAttributesBlacklist

This plugin makes a copy of your app-root and calls it app-root-scully. It leaves all of the original attributes from app-root on the copy. If your app-root has an attribute foo with the value of "bar" then your mock app root (app-root-scully) will also get that attribute.

If you want to make sure that the mock element doesn't get certain attributes, you can use this blacklist to remove certain attributes from the mock element. Example: if the original app-root had foo="bar" as an attribute, and you want to exclude that on the mock copy of it, you would do the following:

getFlashPreventionPlugin({mockAttributesBlacklist: ['foo']});

This would remove the foo attribute from app-root-scully. This looks to see if the attr startsWith the blacklisted item you passed. This means if you pass foo, and the attribute is foobar="baz" it will remove the foobar attribute as it starts with foo.

appRootAttributesBlacklist

This plugin can remove attributes from the pre-rendered version of your app-root. If your app-root had the attribute foo="bar" you can use this blacklist to remove attributes from the source app-root.

getFlashPreventionPlugin({appRootAttributesBlacklist: ['foo']});

This would remove the foo attribute from app-root. This looks to see if the attr startsWith the blacklisted item you passed. This means if you pass foo, and the attribute is foobar="baz" it will remove the foobar attribute as it starts with foo.