fields/merge command

[brandonkelly]

Description

Adds a new fields/merge command, which accepts two custom field handles as arguments, and merges one into the other.

The command will do the following;

1. Update any field layouts that contain instances of the outgoing field, and have those instances point to the persistent field instead.
2. Remove the outgoing field.
3. Generate and run a content migration, which calls afterMergeInto() on the outgoing field, and afterMergeFrom() on the persistent field, giving each field type a chance to react to the merge.

There’s a new MergeableFieldInterface, which field types must implement to opt into being mergeable. The interface defines canMergeInto() and canMergeFrom() methods, giving fields full control over which fields they can be merged with, from both ends of the equation. (By default, the base canMergeInto() and canMergeFrom() implementations will return true if both fields are of the same type, or their dbType() results are considered compatible with each other.)

All core field types except Table are mergeable, at least with other fields of the same type – including Matrix, Addresses, and relational fields.

To propagate the change to other environments, just commit the modified project config YAML files, as well as the generated content migration, and then run craft up on other environments after pulling in the changes. Be sure to answer yes when prompted to run the pending content migration.

Related issues

• Console command for users to merge field definitions #14554

[linear]

CMS-1309 `fields/merge` command

[yeboJoseph]

Could we allow for the second argument to take an array or more than two arguments?
Ex: fields/merge heading [heading1, heading2, heading3, heading20] or fields/merge heading heading1 heading2 heading20
After updating from Craft 4 to 5, I want to merge certain fields into one. Ex: heading1, heading2, heading3, ...heading20. As of now, I'd have to run this command 20 times.
fields/auto-merge won't work in my instance has it merges all fields with the same settings.

[brandonkelly]

(Responded from #16297.)