Day 19: Handling Block Deprecations in Gutenberg

Introduction

Welcome to Day 19 of the Gutenberg series! Today, we’ll explore block deprecations—a critical feature in Gutenberg that allows you to update or refactor blocks without breaking previously published content. When you make changes to a block’s structure, attributes, or output, deprecations help manage the transition smoothly.

In this guide, you’ll learn how to:

• Implement deprecations to handle block updates.
• Safely refactor blocks while maintaining backward compatibility.
• Manage content rendering for older versions of your blocks.

What are Block Deprecations?

Block deprecations allow you to update the definition or behavior of a block without breaking content that was created with an older version of the block. This is especially important when:

• You change a block’s attributes or structure.
• You refactor how a block renders content.
• You modify the block’s settings or inner blocks.

Instead of breaking the content, you use deprecations to support the older block versions, ensuring that users can still edit and view content created with those versions.

Step 1: Basic Block Deprecation Setup

Let’s say you want to update the structure of a Testimonial Block by adding a new rating attribute. You need to ensure that older versions of the block, which do not have this attribute, continue to work without breaking.

1. Define the New Block Version

In your block registration file (e.g., blocks/testimonial-block.js), define the new block version with the added rating attribute.

import { registerBlockType } from '@wordpress/blocks';

registerBlockType('my-theme/testimonial-block', {
    title: 'Testimonial Block',
    icon: 'format-quote',
    category: 'my-custom-category',
    attributes: {
        content: {
            type: 'string',
        },
        rating: {
            type: 'number',
            default: 5,
        },
    },
    edit: ({ attributes, setAttributes }) => {
        const { content, rating } = attributes;

        return (
            <div>
                <textarea
                    value={content}
                    onChange={(event) => setAttributes({ content: event.target.value })}
                    placeholder="Write your testimonial..."
                />
                <input
                    type="number"
                    value={rating}
                    onChange={(event) => setAttributes({ rating: parseInt(event.target.value, 10) })}
                    min={1}
                    max={5}
                />
            </div>
        );
    },
    save: ({ attributes }) => {
        return (
            <div>
                <p>{attributes.content}</p>
                <p>Rating: {attributes.rating} / 5</p>
            </div>
        );
    },
});

Explanation:

• New Attribute: We added a new rating attribute to the Testimonial Block. This allows users to add a rating along with the testimonial text.
• Save Function: The save function now includes the rating value along with the content, ensuring that it’s displayed on the front end.

Step 2: Adding a Deprecation for the Older Block Version

Since older versions of the block don’t have the rating attribute, we need to define a deprecated version that handles content created before the update.

1. Add the Deprecation to the Block Definition

To add a deprecation, include a deprecations array in your block definition that describes how to handle older versions.

registerBlockType('my-theme/testimonial-block', {
    title: 'Testimonial Block',
    icon: 'format-quote',
    category: 'my-custom-category',
    attributes: {
        content: {
            type: 'string',
        },
        rating: {
            type: 'number',
            default: 5,
        },
    },
    edit: ({ attributes, setAttributes }) => {
        const { content, rating } = attributes;

        return (
            <div>
                <textarea
                    value={content}
                    onChange={(event) => setAttributes({ content: event.target.value })}
                    placeholder="Write your testimonial..."
                />
                <input
                    type="number"
                    value={rating}
                    onChange={(event) => setAttributes({ rating: parseInt(event.target.value, 10) })}
                    min={1}
                    max={5}
                />
            </div>
        );
    },
    save: ({ attributes }) => {
        return (
            <div>
                <p>{attributes.content}</p>
                <p>Rating: {attributes.rating} / 5</p>
            </div>
        );
    },
    deprecations: [
        {
            attributes: {
                content: { type: 'string' },
            },
            save: ({ attributes }) => {
                return <p>{attributes.content}</p>; // Only render the content for the older version
            },
        },
    ],
});

Explanation:

• Deprecation: We define a deprecation that handles the older version of the block. Since the old block didn’t have the rating attribute, we only save the content attribute.
• Fallback Save Function: The deprecated save function ensures that old blocks will render correctly by only showing the testimonial content, without trying to render the missing rating.

Step 3: Updating the Block Version Without Breaking Content

You can now safely update your block without worrying about breaking previously published content. WordPress will continue to recognize and render the older block version using the deprecation logic.

1. Rebuild the Block:
   • Make sure to rebuild your block after adding the deprecation.

npm run build

2. Test with Older Content:
   • Edit a post or page with older Testimonial Blocks (those created before the update). Confirm that they render correctly, showing only the testimonial content.
   • Add new Testimonial Blocks with the rating feature to verify that both versions coexist without issues.

Step 4: Adding Multiple Deprecations for Complex Blocks

In some cases, blocks evolve over time with multiple updates. You can add multiple deprecations to handle different versions of the block, ensuring backward compatibility for each.

1. Add Multiple Deprecations

If your block has gone through several versions, you can define multiple deprecations.

deprecations: [
    // Version 1 (without rating)
    {
        attributes: {
            content: { type: 'string' },
        },
        save: ({ attributes }) => {
            return <p>{attributes.content}</p>;
        },
    },
    // Version 2 (with rating but no date)
    {
        attributes: {
            content: { type: 'string' },
            rating: { type: 'number' },
        },
        save: ({ attributes }) => {
            return (
                <div>
                    <p>{attributes.content}</p>
                    <p>Rating: {attributes.rating} / 5</p>
                </div>
            );
        },
    },
],

Explanation:

• Multiple Versions: We define two deprecations—one for the original block (without rating) and one for a later version that had the rating but didn’t include a date.

Best Practices for Handling Block Deprecations

1. Ensure Backward Compatibility: Always add a deprecation when changing a block’s structure, attributes, or output to prevent breaking existing content.
2. Handle Multiple Versions: If your block has gone through several updates, consider adding multiple deprecations to handle each version.
3. Test Thoroughly: Always test older block versions in the editor and on the front end to ensure that content renders as expected across different versions.

Conclusion: Managing Block Updates with Deprecations

Block deprecations are a vital feature for managing updates in Gutenberg without breaking existing content. By defining deprecations for each version of your block, you can safely refactor blocks, add new features, or change their structure while ensuring backward compatibility.

In this article, you’ve learned how to:

• Add deprecations to handle older block versions.
• Safely update blocks while maintaining backward compatibility.
• Test block updates with real content to ensure smooth transitions.

In Day 20, we’ll cover custom block variations, allowing you to define multiple styles or presets for a single block.