Deprecated function not working in Gutenberg

Question

I'm change the default attributes:

const blockAttrs = {
        avatarSize: {
            type: 'number',
            default: 120, // 70 -> 120
        },
        //other attrs
      };

Deprecated function:

deprecated: [
            {
                attributes: {
                    ...blockAttrs,
                    avatarSize: {
                        type: 'number',
                        default: 70
                    }
                },
                save: function ( { attributes } ) {}
            }
        ]

But when i refresh post, block still display error:

Someone

Answer 1

Looking at the documentation from https://developer.wordpress.org/block-editor/developers/block-api/block-deprecation/

I think you may need the following

 migrate( { text } ) {
            return {
                content: text
            };
        },

So in your case:

migrate( { avatarSize } ) {
            avatarSize: {
                    type: 'number',
                    default: 70
                }  content: text
            };
        },

Hopefully points you in the correct direction

Answer 2

Your save function needs to return a valid React component or null.

save: function ( { attributes } ) {}

should be

save: function ( { attributes } ) { return null; }