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Remove Application wrapper div (#280)
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| - Start Date: 2017-12-11 | ||
| - RFC PR: https://github.com/emberjs/rfcs/pull/280 | ||
| - Ember Issue: https://github.com/emberjs/ember.js/pull/15981 | ||
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| # Summary | ||
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| Introduce a low-level "flag" to remove the automatic wrapper `<div>` around | ||
| Ember apps and tests. | ||
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| # Motivation | ||
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| In Ember applications today, applications are anchored to some existing HTML | ||
| element in the page. Usually, this element is the `<body>` of the document, but it | ||
| can be configured to be a different one when the application is defined, | ||
| passing a CSS selector to the `rootElement` property: | ||
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| ```js | ||
| export default Ember.Application.extend({ | ||
| rootElement: '#app' | ||
| }); | ||
| ``` | ||
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| However, whatever the root is, the application adds another `<div>` wrapper | ||
| that is not required anymore. It's a vestigial remainder of some implementation | ||
| detail of how views worked in Ember 1.x. Some sort of wisdom tooth of the original | ||
| rendering system that serves no purpose today. | ||
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| Furthermore, much like a wisdom tooth, it can give us problems. In the past, this element | ||
| was configurable using the `ApplicationView`, but when views were removed we lost that | ||
| ability. Right now we are stuck with a wrapper element we can't remove nor customize, | ||
| which is why some apps target the selector `body > .ember-view` to style this element. | ||
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| Similarly, in testing there is another `.ember-view` wrapper inside the | ||
| `#ember-testing` container for no good reason. | ||
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| This RFC proposes to add a global flag to remove those wrapper elements, | ||
| effectively making the `application.hbs` template have "Outer HTML" semantics, which aligns | ||
| well with [the changes recently proposed](https://github.com/emberjs/rfcs/pull/278) | ||
| for template-only components, as well as the way Glimmer apps work. | ||
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| The same flag will also remove the unnecessary extra wrapper inside the testing | ||
| container. | ||
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| # Detailed design | ||
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| ## API Surface | ||
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| The proposed approach is identical to the one proposed in #278, quoted below: | ||
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| > We should not expose the flag directly as a public API. Instead, we should | ||
| abstract the flag with a "privileged addon" whose only purpose is to enable | ||
| the flag. Applications will enable the flag by installing this addon. This | ||
| will allow for more flexibility in changing the flag's implementation (the | ||
| location, naming, value, or even the existence of it) in the future. From the | ||
| user's perspective, it is the addon that provides this functionality. The | ||
| flag is simply an internal implementation detail. | ||
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| > We have done this before in other cases (such as the legacy view addon during | ||
| the 2.0 transition period), and it has generally worked well. | ||
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| > When landing this feature, it will be entirely opt-in for existing apps, but | ||
| the Ember CLI application blueprint should be updated to include the addon by | ||
| default. At a later time, we should provide another addon that _disables_ the | ||
| flag explicitly (installing both addons would be an install-time error). At | ||
| that time, we will issue a deprecation warning if the flag is *not set*, with | ||
| a message that directs the user to install one of the two addons. | ||
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| ## Migration Path | ||
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| Given that this change only affects one single point in your application, | ||
| I do not believe we need any specific strategy. If the users want to bring | ||
| back the wrapper because it breaks their styles or some other reason, | ||
| they can just add it manually on the `application.hbs` template, with | ||
| any class or id they want. | ||
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| # How We Teach This | ||
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| This addon will be opt-in, but at some point it will become part of | ||
| the default blueprint. This change, rather than introducing a new concept, *removes* | ||
| an old one. Users won't have to google what is the way to remove or customize | ||
| the implicit application wrapper of the app (to sadly discover that is not | ||
| even possible), but instead they will add a wrapper only if they want, | ||
| and in the same way they would add a wrapper in any other point of their application, | ||
| with regular Handlebars. | ||
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| # Drawbacks | ||
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| There is a possibility that removing the wrapper can break styles for some apps, | ||
| but since adding the wrapper back is just editing the `application.hbs` template, | ||
| that is probably a minor drawback. | ||
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| There is also a non-zero chance that some testing addon is relying on the `#ember-testing > .ember-view` | ||
| HTML hierarchy for some reason, and those addons would have to be updated. | ||
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| # Alternatives | ||
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| Leave things as they are today. |