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Deprecate module pattern (factory) components #15145

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merged 1 commit into from Mar 19, 2019

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commented Mar 19, 2019

This is part of reactjs/rfcs#107 but it's not the only reason we want to deprecate it.

It requires a fairly complex code path in React that is forked from how class components are initialized. It makes function components slower, adds code bloat to React and is a maintenance burden.

It was really kind of supported from the beginning. It was originally added at a time where createClass and class-like abstractions were more popular. We also hit quirks with compile-to-JS languages when we changed how our class abstractions worked. E.g. we had to make accommodations to support ScalaJS. To avoid future problems, we kept this style of class working since it's really the simplest form of constructor in JavaScript.

However, since then when we ultimately supported both ES classes (must be called with new) and arrow function components (cannot be called with new), we had to start getting more selective about which components we call with new and which we don't.

In practice, I don't think this pattern has been widely used even by compile to JS languages or class-like abstractions.

In any official capacity, its support has only been briefly noted at the bottom of the React v0.13.0 Beta 1 post.

It is currently used by at least Relay Classic so some libraries will need to upgrade.

A neat trick is that you can almost always just add:

Foo.prototype = React.Component.prototype;

This tricks React's class detection into thinking it's a class and we'll call it with new, which means that this doesn't work on arrow functions.

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commented Mar 19, 2019

ReactDOM: size: 0.0%, gzip: -0.0%

Details of bundled changes.

Comparing: 1e3364e...aa4d7ff

react-dom

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@edvinerikson

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commented Mar 19, 2019

The Relay Classic reference seems to be used in Relay Modern, but that's the only case in OSS that I've seen using this pattern.

@sebmarkbage

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commented Mar 19, 2019

I have a diff open internally to fix the Relay caller.

@sebmarkbage sebmarkbage merged commit acd65db into facebook:master Mar 19, 2019

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facebook-github-bot added a commit to facebook/relay that referenced this pull request Mar 19, 2019

Trick React into thinking a container is a class
Summary:
The factory component pattern is about to be deprecate in:

facebook/react#15145

This change makes it so that React will call this constructor with `new` as if
it is a class component instead of just calling it as a function component.

There might be a slight perf penalty to doing this my understanding is that this
is not the preferred path anyway.

Reviewed By: kassens

Differential Revision: D14516681

fbshipit-source-id: 751890a98639687b208633f2e4c8e71e5df60776

Kiku-Reise added a commit to Kiku-Reise/react that referenced this pull request May 16, 2019

@gaearon gaearon referenced this pull request Jul 30, 2019
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