@wordpress/blocks/build-module/api/parser/apply-block-deprecated-versions.js

Block API for WordPress.

/**
 * Internal dependencies
 */
import { DEPRECATED_ENTRY_KEYS } from '../constants';
import { validateBlock } from '../validation';
import { getBlockAttributes } from './get-block-attributes';
import { applyBuiltInValidationFixes } from './apply-built-in-validation-fixes';
import { omit } from '../utils';

/**
 * Function that takes no arguments and always returns false.
 *
 * @return {boolean} Always returns false.
 */
function stubFalse() {
  return false;
}

/**
 * Given a block object, returns a new copy of the block with any applicable
 * deprecated migrations applied, or the original block if it was both valid
 * and no eligible migrations exist.
 *
 * @param {import(".").WPBlock}                   block     Parsed and invalid block object.
 * @param {import(".").WPRawBlock}                rawBlock  Raw block object.
 * @param {import('../registration').WPBlockType} blockType Block type. This is normalize not necessary and
 *                                                          can be inferred from the block name,
 *                                                          but it's here for performance reasons.
 *
 * @return {import(".").WPBlock} Migrated block object.
 */
export function applyBlockDeprecatedVersions(block, rawBlock, blockType) {
  const parsedAttributes = rawBlock.attrs;
  const {
    deprecated: deprecatedDefinitions
  } = blockType;
  // Bail early if there are no registered deprecations to be handled.
  if (!deprecatedDefinitions || !deprecatedDefinitions.length) {
    return block;
  }

  // By design, blocks lack any sort of version tracking. Instead, to process
  // outdated content the system operates a queue out of all the defined
  // attribute shapes and tries each definition until the input produces a
  // valid result. This mechanism seeks to avoid polluting the user-space with
  // machine-specific code. An invalid block is thus a block that could not be
  // matched successfully with any of the registered deprecation definitions.
  for (let i = 0; i < deprecatedDefinitions.length; i++) {
    // A block can opt into a migration even if the block is valid by
    // defining `isEligible` on its deprecation. If the block is both valid
    // and does not opt to migrate, skip.
    const {
      isEligible = stubFalse
    } = deprecatedDefinitions[i];
    if (block.isValid && !isEligible(parsedAttributes, block.innerBlocks, {
      blockNode: rawBlock,
      block
    })) {
      continue;
    }

    // Block type properties which could impact either serialization or
    // parsing are not considered in the deprecated block type by default,
    // and must be explicitly provided.
    const deprecatedBlockType = Object.assign(omit(blockType, DEPRECATED_ENTRY_KEYS), deprecatedDefinitions[i]);
    let migratedBlock = {
      ...block,
      attributes: getBlockAttributes(deprecatedBlockType, block.originalContent, parsedAttributes)
    };

    // Ignore the deprecation if it produces a block which is not valid.
    let [isValid] = validateBlock(migratedBlock, deprecatedBlockType);

    // If the migrated block is not valid initially, try the built-in fixes.
    if (!isValid) {
      migratedBlock = applyBuiltInValidationFixes(migratedBlock, deprecatedBlockType);
      [isValid] = validateBlock(migratedBlock, deprecatedBlockType);
    }

    // An invalid block does not imply incorrect HTML but the fact block
    // source information could be lost on re-serialization.
    if (!isValid) {
      continue;
    }
    let migratedInnerBlocks = migratedBlock.innerBlocks;
    let migratedAttributes = migratedBlock.attributes;

    // A block may provide custom behavior to assign new attributes and/or
    // inner blocks.
    const {
      migrate
    } = deprecatedBlockType;
    if (migrate) {
      let migrated = migrate(migratedAttributes, block.innerBlocks);
      if (!Array.isArray(migrated)) {
        migrated = [migrated];
      }
      [migratedAttributes = parsedAttributes, migratedInnerBlocks = block.innerBlocks] = migrated;
    }
    block = {
      ...block,
      attributes: migratedAttributes,
      innerBlocks: migratedInnerBlocks,
      isValid: true,
      validationIssues: []
    };
  }
  return block;
}
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