Black Lives Matter.

Emotion 11 is a slight evolution over the Emotion 10. It focuses mainly on the developer experience, TS types improvements, switches internals to hooks and to the new version of the parser that we use: Stylis.

Package renaming

One of the most significant changes is that most of the user-facing packages have been renamed.

Most of this renaming can be done automatically via a codemod, following these steps:

  1. Install @emotion/eslint-plugin
  2. Add it as a plugin to .eslintrc
  3. Add Emotion 11 codemod rule
  4. Run eslint with the --fix flag. For example: yarn eslint --config .eslintrc --ext .js,.jsx "." --fix

The full list of renamed packages:

  • @emotion/core@emotion/react
  • emotion@emotion/css
  • emotion-theming → moved into @emotion/react
  • emotion-server@emotion/server
  • create-emotion@emotion/css/create-instance
  • create-emotion-server@emotion/server/create-instance
  • babel-plugin-emotion@emotion/babel-plugin
  • eslint-plugin-emotion@emotion/eslint-plugin
  • jest-emotion@emotion/jest

Hooks

Use hooks internally for improved bundle size and a better tree in React DevTools 🎉.

TypeScript

Types overhaul

TypeScript types have been significantly restructured.

  • reduce build times when using Emotion, especially in larger projects
  • it’s no longer necessary to manually specify generic parameters for your Emotion components in many cases
  • union types as props are better supported and should be inferred properly
  • the css function has been restricted to prevent passing invalid types
  • styled’s generic parameter has been changed, if you were specifying the ComponentType you will need to remove that generic parameter
  • styled no longer takes a second ExtraProps parameter - instead of that move it to after the styled call. So instead of writing styled<typeof MyComponent, ExtraProps>(MyComponent)({}) you should now be writing styled(MyComponent)<ExtraProps>({})

If you encounter build issues after upgrade, try removing any manually specified generic types and let them be inferred.

Theme type

It’s now easier to provide a type for Theme. Instead of creating custom instances (like before) you can augment the builtin Theme interface like this:

import '@emotion/react'

declare module '@emotion/react' {
  export interface Theme {
    primaryColor: string
    secondaryColor: string
  }
}

css prop types

The way in which we provide TypeScript support for the css prop has changed. Based on the usage of our JSX factories, we can add support for css prop only for components that support className prop (as our JSX factory functions take the provided css prop, resolve it and pass the generated className to the rendered component).

For the classic runtime this has been implemented using technique described here. What is important - we no longer extend any global interfaces, so people shouldn’t bump anymore into type conflicts for the css prop when using different libraries with css prop support, such as styled-components.

For the automatic runtime this has been implemented by exporting JSX namespace from the appropriate entries but this is only supported in TypeScript 4.1 or higher.

However, if you are stuck with older version of TypeScript or using the classic runtime implicitly by using our @emotion/babel-preset-css-prop then it’s not possible to leverage leverage css prop support being added conditionally based on a type of rendered component. For those cases we have added a special file that can be imported once to add support for the css prop globally, for all components. Use it like this:

/// <reference types="@emotion/react/types/css-prop" />

In this particular case we are forced to extend the existing React.Attributes interface. Previously we’ve been extending both React.DOMAttributes and JSX.IntrinsicAttributes. This change is really minor and shouldn’t affect any consuming code.

Stylis v4

The parser we use (Stylis) got upgraded. It fixes some long-standing parsing edge cases while being smaller and faster 🚀

It has been completely rewritten and comes with some breaking changes. The most notable ones that might affect Emotion users are:

  • plugins written for the former Stylis v3 are not compatible with the new version. To learn more on how to write a plugin for Stylis v4 you can check out its README and the source code of core plugins.
  • vendor-prefixing was previously customizable using prefix option. This was always limited to turning off all of some of the prefixes as all available prefixes were on by default. The prefix option is gone and to customize which prefixes are applied you need to fork (copy-paste) the prefixer plugin and adjust it to your needs. While this being somewhat more problematic to setup at first we believe that the vast majority of users were not customizing this anyway. By not including the possibility to customize this through an extra option the final solution is more performant because there is no extra overhead of checking if a particular property should be prefixed or not.
  • the prefixer is now just a plugin which happens to be included in the default stylisPlugins. If you plan to use custom stylisPlugins and you want to have your styles prefixed automatically you must include prefixer in your custom stylisPlugins. You can import prefixer from the stylis module to do that.
  • @import rules are no longer special-cased. The responsibility to put them first has been moved to the author of the styles. They also can’t be nested within other rules now. It’s only possible to write them at the top level of global styles.

Emotion’s caches

The key option is now required when creating a custom instance of a cache. Please make sure it’s unique (and not equal to 'css') as it’s used for linking styles to your cache. If multiple caches share the same key they might “fight” for each other’s style elements.

The new prepend option can make Emotion add style tags at the beginning of the specified DOM container instead of the end.

Other

There are a lot of less substantial changes than what has been described here, some of them might even be breaking changes but are not relevant to the majority of users. Therefore to learn more about all of the changes please read through the full list of changes contained in the respective changelogs:

@emotion/babel-plugin @emotion/babel-preset-css-prop @emotion/cache @emotion/css @emotion/eslint-plugin @emotion/is-prop-valid @emotion/jest @emotion/native @emotion/primitives-core @emotion/primitives @emotion/react @emotion/serialize @emotion/server @emotion/sheet @emotion/styled @emotion/utils