rich-text-contentful-serializer

This package contains utilities to convert Contentful Rich Text to a Rich Text rast (Rich Text Abstract Syntax Tree) document.

Please refer to the rast format docs to learn more about the syntax tree format and the available nodes.

Usage

The main utility in this package is contentfulToRichText which takes a Rich Text JSON and transforms it into a valid rast document.

contentfulToRichText returns a Promise that resolves with a Rich Text document.

import { contentfulToRichText } from 'rich-text-contentful-serializer';

const richText = {
  nodeType: 'document',
  data: {},
  content: [
    {
      nodeType: 'heading-1',
      content: [
        {
          nodeType: 'text',
          value: 'Lorem ipsum dolor sit amet',
          marks: [],
          data: {},
        },
      ],
      data: {},
    },
};

contentfulToRichText(richText).then((richText) => {
  console.log(richText);
});

Validate rast documents

rast is a strict format for Rich Text fields and follows a different pattern from Contentful Rich Text structure.

The rich-text-utils package provides a validate utility to validate a Rich Text content to make sure that it is compatible with Rich Text field.

import { validate } from 'rich-text-utils';

// ...

contentfulToRichText(richText).then((richText) => {
  const { valid, message } = validate(richText);

  if (!valid) {
    throw new Error(message);
  }
});

We recommend to validate every rast to avoid errors later when creating records.

Advanced Usage

Options

All the *ToRichText utils accept an optional options object as second argument:

type Options = Partial<{
  // Override existing Contentful node handlers or add new ones.
  handlers: Record<string, CreateNodeFunction>,
  // Array of allowed Block nodes.
  allowedBlocks: Array<
    BlockquoteType | CodeType | HeadingType | LinkType | ListType,
  >,
  // Array of allowed marks.
  allowedMarks: Mark[],
}>;

Transforming Nodes

The utils in this library traverse a Contentful Rich Text tree and transform supported nodes to rast nodes. The transformation is done by working on a Contentful Rich Text node with a handler (async) function.

Handlers are associated to Contentful Rich Text nodes by nodeType and look as follow:

import { visitChildren } from 'rich-text-contentful-serializer';

// Handler for the paragraph node type.
async function p(createrastNode, contentfulNode, context) {
  return createrastNode('paragraph', {
    children: await visitChildren(createrastNode, contentfulNode, context),
  });
}

Handlers can return either a promise that resolves to a rast node, an array of rast Nodes, or undefined to skip the current node.

To ensure that a valid rast is generated, the default handlers also check that the current contentfulNode is a valid rast node for its parent and, if not, they ignore the current node and continue visiting its children.

Information about the parent rast node name is available in context.parentNodeType.

Please take a look at the default handlers implementation for examples.

The default handlers are available on context.defaultHandlers.

Context

Every handler receives a context object that includes the following information:

export interface GlobalContext {
  // <base> tag url. This is used for resolving relative URLs.
  baseUrl?: string;
}

export interface Context {
  // The current parent `rast` node type.
  parentNodeType: NodeType;
  // The parent `Contentful Rich Text` node.
  parentNode: ContentfulNode;
  // A reference to the current handlers - merged default + user handlers.
  handlers: Record<string, Handler<unknown>>;
  // A reference to the default handlers record (map).
  defaultHandlers: Record<string, Handler<unknown>>;
  // Marks for span nodes.
  marks?: Mark[];
  // Array of allowed Block types.
  allowedBlocks: Array<
    BlockquoteType | CodeType | HeadingType | LinkType | ListType,
  >;
  // Array of allowed marks.
  allowedMarks: Mark[];
  // Properties in this object are available to every handler as Context
  // is not deeply cloned.
  global: GlobalContext;
}

Custom Handlers

It is possible to register custom handlers and override the default behaviour via options:

import { paragraphHandler } from './customHandlers';

contentfulToRichText(richText, {
  handlers: {
    paragraph: paragraphHandler,
  },
}).then((richText) => {
  console.log(richText);
});

It is highly encouraged to validate the rast when using custom handlers because handlers are responsible for dictating valid parent-children relationships and therefore generating a tree that is compliant with Rich Text.

Preprocessing Rich Text

Because of the strictness of the rast spec, it is possible that some elements might be lost during transformation.

To improve the final result, you might want to modify the Rich Text tree before it is transformed to rast.

Examples

const richTextWithAssets = {
  nodeType: 'document',
  data: {},
  content: [
    {
      nodeType: 'unordered-list',
      content: [
        {
          nodeType: 'list-item',
          content: [
            {
              nodeType: 'paragraph',
              content: [
                {
                  nodeType: 'text',
                  value: 'text',
                  marks: [],
                  data: {},
                },
              ],
              data: {},
            },
            {
              content: [],
              data: {
                target: {
                  sys: {
                    id: 'zzz',
                    linkType: 'Asset',
                    type: 'Link',
                  },
                },
              },
              nodeType: 'embedded-asset-block',
            },
            {
              nodeType: 'paragraph',
              content: [
                {
                  nodeType: 'text',
                  value: 'text',
                  marks: [],
                  data: {},
                },
              ],
              data: {},
            },
          ],
          data: {},
        },
      ],
      data: {},
    },
  ],
};

// This function transforms the richText tree and moves the embedded-asset-block to root,
// splitting the list in two parts.

function liftAssets(richText) {
  const visit = (node, cb, index = 0, parents = []) => {
    if (node.content && node.content.length > 0) {
      node.content.forEach((child, index) => {
        visit(child, cb, index, [...parents, node]);
      });
    }

    cb(node, index, parents);
  };

  const liftedImages = new WeakSet();

  visit(richText, (node, index, parents) => {
    if (
      !node ||
      node.nodeType !== 'embedded-asset-block' ||
      liftedImages.has(node) ||
      parents.length === 1 // is a top level asset
    ) {
      return;
    }

    const imgParent = parents[parents.length - 1];

    imgParent.content.splice(index, 1);

    let i = parents.length;
    let splitChildrenIndex = index;
    const contentAfterSplitPoint = [];

    while (--i > 0) {
      const parent = parents[i];
      const parentsParent = parents[i - 1];

      contentAfterSplitPoint = parent.content.splice(splitChildrenIndex);

      splitChildrenIndex = parentsParent.content.indexOf(parent);

      let nodeInserted = false;

      if (i === 1) {
        splitChildrenIndex += 1;
        parentsParent.content.splice(splitChildrenIndex, 0, node);
        liftedImages.add(node);

        nodeInserted = true;
      }

      splitChildrenIndex += 1;

      if (contentAfterSplitPoint.length > 0) {
        parentsParent.content.splice(splitChildrenIndex, 0, {
          ...parent,
          content: contentAfterSplitPoint,
        });
      }
      // Remove the parent if empty
      if (parent.content.length === 0) {
        splitChildrenIndex -= 1;
        parentsParent.content.splice(
          nodeInserted ? splitChildrenIndex - 1 : splitChildrenIndex,
          1,
        );
      }
    }
  });
}

liftAssets(richTextWithAssets);

const handlers = {
  'embedded-asset-block': async (createNode, node, context) => {
    const entry = '123';
    return createNode('block', {
      entry,
    });
  },
};

const rast = await contentfulToRichText(richTextWithAssets, { handlers });

License

MIT