CSSPropertyOperations.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {shorthandToLonghand} from './CSSShorthandProperty';

import dangerousStyleValue from './dangerousStyleValue';
import hyphenateStyleName from './hyphenateStyleName';
import warnValidStyle from './warnValidStyle';
import warning from 'shared/warning';

/**
 * Operations for dealing with CSS properties.
 */

/**
 * This creates a string that is expected to be equivalent to the style
 * attribute generated by server-side rendering. It by-passes warnings and
 * security checks so it's not safe to use this value for anything other than
 * comparison. It is only used in DEV for SSR validation.
 */
export function createDangerousStringForStyles(styles) {
  if (__DEV__) {
    let serialized = '';
    let delimiter = '';
    for (const styleName in styles) {
      if (!styles.hasOwnProperty(styleName)) {
        continue;
      }
      const styleValue = styles[styleName];
      if (styleValue != null) {
        const isCustomProperty = styleName.indexOf('--') === 0;
        serialized += delimiter + hyphenateStyleName(styleName) + ':';
        serialized += dangerousStyleValue(
          styleName,
          styleValue,
          isCustomProperty,
        );

        delimiter = ';';
      }
    }
    return serialized || null;
  }
}

/**
 * Sets the value for multiple styles on a node.  If a value is specified as
 * '' (empty string), the corresponding style property will be unset.
 *
 * @param {DOMElement} node
 * @param {object} styles
 */
export function setValueForStyles(node, styles) {
  const style = node.style;
  for (let styleName in styles) {
    if (!styles.hasOwnProperty(styleName)) {
      continue;
    }
    const isCustomProperty = styleName.indexOf('--') === 0;
    if (__DEV__) {
      if (!isCustomProperty) {
        warnValidStyle(styleName, styles[styleName]);
      }
    }
    const styleValue = dangerousStyleValue(
      styleName,
      styles[styleName],
      isCustomProperty,
    );
    if (styleName === 'float') {
      styleName = 'cssFloat';
    }
    if (isCustomProperty) {
      style.setProperty(styleName, styleValue);
    } else {
      style[styleName] = styleValue;
    }
  }
}

function isValueEmpty(value) {
  return value == null || typeof value === 'boolean' || value === '';
}

/**
 * Given {color: 'red', overflow: 'hidden'} returns {
 *   color: 'color',
 *   overflowX: 'overflow',
 *   overflowY: 'overflow',
 * }. This can be read as "the overflowY property was set by the overflow
 * shorthand". That is, the values are the property that each was derived from.
 */
function expandShorthandMap(styles) {
  const expanded = {};
  for (const key in styles) {
    const longhands = shorthandToLonghand[key] || [key];
    for (let i = 0; i < longhands.length; i++) {
      expanded[longhands[i]] = key;
    }
  }
  return expanded;
}

/**
 * When mixing shorthand and longhand property names, we warn during updates if
 * we expect an incorrect result to occur. In particular, we warn for:
 *
 * Updating a shorthand property (longhand gets overwritten):
 *   {font: 'foo', fontVariant: 'bar'} -> {font: 'baz', fontVariant: 'bar'}
 *   becomes .style.font = 'baz'
 * Removing a shorthand property (longhand gets lost too):
 *   {font: 'foo', fontVariant: 'bar'} -> {fontVariant: 'bar'}
 *   becomes .style.font = ''
 * Removing a longhand property (should revert to shorthand; doesn't):
 *   {font: 'foo', fontVariant: 'bar'} -> {font: 'foo'}
 *   becomes .style.fontVariant = ''
 */
export function validateShorthandPropertyCollisionInDev(
  styleUpdates,
  nextStyles,
) {
  if (!nextStyles) {
    return;
  }

  const expandedUpdates = expandShorthandMap(styleUpdates);
  const expandedStyles = expandShorthandMap(nextStyles);
  const warnedAbout = {};
  for (const key in expandedUpdates) {
    const originalKey = expandedUpdates[key];
    const correctOriginalKey = expandedStyles[key];
    if (correctOriginalKey && originalKey !== correctOriginalKey) {
      const warningKey = originalKey + ',' + correctOriginalKey;
      if (warnedAbout[warningKey]) {
        continue;
      }
      warnedAbout[warningKey] = true;
      warning(
        false,
        '%s a style property during rerender (%s) when a ' +
          'conflicting property is set (%s) can lead to styling bugs. To ' +
          "avoid this, don't mix shorthand and non-shorthand properties " +
          'for the same value; instead, replace the shorthand with ' +
          'separate values.',
        isValueEmpty(styleUpdates[originalKey]) ? 'Removing' : 'Updating',
        originalKey,
        correctOriginalKey,
      );
    }
  }
}