Passing style to child component without using global styles

[pruhstal]

I've got a child component, let's call it Link.

This is the code for that:

import React from 'react';
import Link from 'next/link';

export default class CustomLink extends React.Component {
  render() {
    if (this.props.onClick) {
      return (
        <span className={this.props.className} onClick={this.props.onClick}>
          {this.props.children}
        </span>
      );
    }

    return (
      <Link
        href={this.props.href}
        params={this.props.params}
        as={this.props.as}>
        <a className={this.props.className}>{this.props.children}</a>
      </Link>
    );
  }
}

Now say that I import that component within another component, called Header

The code for that is:

import Link from './Link';

export default class Header extends React.Component {
  render() {
    return (
      <div className="root">
        <style jsx>{`
          .link {
            background-color: #fff;
            border-bottom: 1px solid #eee;
            color: #222;
          }
          `}
        </style>
       <Link className="link">Click me</Link>
    );
  }
}

However, unless I use <style jsx global>, then unfortunately the style doesn't get passed to the child component.

I think a related issue is #197, but I haven't seen any outcome or update on that issue since June.

Is there a solution to fixing this issue?

[pruhstal]

So it seems if I do this:

          .root .link {
            display: inline-block;
            border-bottom: 2px solid transparent;
            padding: 0 15px;
            text-decoration: none;
            text-transform: uppercase;
          }

          .root .link,
          .root .link:active,
          .root .link:visited {
            color: #222;
          }

          .root .link.active,
          .root .link:hover {
            border-bottom: 2px solid #222;
            color: #222;
          }

It seems to work.

Alternatively I can also do:

          :global(.link) {
            display: inline-block;
            border-bottom: 2px solid transparent;
            padding: 0 15px;
            text-decoration: none;
            text-transform: uppercase;
          }

          :global(.link),
          :global(.link:active),
          :global(.link:visited) {
            color: #222;
          }

          :global(.link.active),
          :global(.link:hover) {
            border-bottom: 2px solid #222;
            color: #222;
          }

from the parent component's styles.

What is the right thing to do here?

[colinmeinke]

I think the the modifier/variant styles should be applied to the Link component, not the component in which they are used.

import React from 'react';
import Link from 'next/link';

export default class CustomLink extends React.Component {
  render() {
    if (this.props.onClick) {
      return (
        <span className={this.props.className} onClick={this.props.onClick}>
          {this.props.children}
        </span>
      );
    }

    return (
      <Link
        href={this.props.href}
        params={this.props.params}
        as={this.props.as}>
        <a className={this.props.className}>{this.props.children}</a>
        <style jsx>{`
          .link {
            background-color: #fff;
            border-bottom: 1px solid #eee;
            color: #222;
          }
        `}</style>
      </Link>
    );
  }
}

use:

import Link from './Link';

export default class Header extends React.Component {
  render() {
    return (
      <div>
        <Link className="link">Click me</Link>
      </div>
    );
  }
}

[pruhstal]

@colinmeinke that doesn't really work well, because what if Link comes from some npm module (e.g. a UI library), and I don't have control over it?

That's the use case where this becomes a real problem.

[giuseppeg]

what if Link comes from some npm module (e.g. a UI library), and I don't have control over it?

That's the main point, we'd have to figure out a way to control styles from the parent because passing a prop (eg. className) is an half baked solution that won't work all the times.

As for now the best way to do this is to use .someSelectorInTheParentComponent > :global() from within the parent component eg.

<div className="root">
    <Link />
    <style jsx>{`
        .root > :global(a) { font-size: 60px }
     `}</style>
</div>

[a-ignatov-parc]

I've found a better workaround for this issue.

function HighlightedLink(props) {
  const {
    theme,
    children,
    ...otherProps,
  } = props;

  /**
   * `scope` element is needed to properly parse `style` element
   * and it could be any DOM element you want.
   */
  const scope = resolveScopedStyles((
    <scope>
      <style jsx>{`
        .link {
          background: ${theme.background};
        }
      `}</style>
    </scope>
  ));

  return (
    <Link
      {...otherProps}
      className={scope.wrapClassNames('link')}
    >
      {children}
      <scope.styles />
    </Link>
  );
}

function resolveScopedStyles(scope) {
  return {
    className: scope.props.className,
    styles: () => scope.props.children,
    wrapClassNames: (...classNames) => [scope.props.className, ...classNames].filter(Boolean).join(' '),
  };
}

[giuseppeg]

@a-ignatov-parc it might add some runtime overhead but it is genius! :D

[a-ignatov-parc]

might add some runtime overhead

Yeah. But usually you shouldn't use child combinator selectors. Child component's markup is its private area and may change at any time.

[giuseppeg]

But usually you shouldn't use child combinator selectors

Agreed, unfortunately that's the only way to style 3rd parties components that don't accept a className.

By the way styles could be just scope.props.children and used like this {scope.styles}. You could expose Styles: () => scope.props.children and styles: scope.props.children :)

I've been thinking to implement automatic className propagation for components and support this syntax:

<Link className="link">
  {children}
  <style jsx>{`
     .link { background: ${theme.background} }
  `}</style>
</Link>

Although I like the explicitness of your solution since on can do anything with the className and styles.
Today I am giving a talk about styled-jsx if it is ok with you I would like to use your example (with credits) in my presentation.

[a-ignatov-parc]

You could expose Styles: () => scope.props.children and styles: scope.props.children

Sounds good 👍

I would like to use your example (with credits) in my presentation.

Sure 😉

[a-ignatov-parc]

Agreed, unfortunately that's the only way to style 3rd parties components that don't accept a className.

True. But it's better to choose another component/lib than apply such implicit styling. No one likes magic that can break your UI.

[giuseppeg]

Added @a-ignatov-parc workaround to the docs:

https://github.com/zeit/styled-jsx#styling-third-parties--child-components-from-the-parent