Fix sequence action copy-paste

[karwosts]

Proposed change

When using Ctrl-C + Ctrl-V to copy/paste a sequence building block inside a script, the paste action does not paste the sequence, but instead cracks it and pastes the individual items, but not the building block.

This is because

sequence:
  - action: ...

is ambiguous, it could be a script with one action, or it could be a building block element inside a script with one action.

To fix this to behave as expected, when we copy a sequence building block in the visual editor, we can use metadata to differentiate that it is a building block and not a complete script. So we will put on the clipboard:

sequence:
  - action: ...
metadata: {}

Then in handlePaste, if we detect a sequence with metadata, we know for sure that it is a building block and can do the paste correctly.

This was almost fully clean solution, except that if you Ctrl-C this and paste it in yaml, it is unsaveable, because core will reject a sequence with a metadata object. So I make a core change as well to allow metadata on a sequence building block, same as how we allow it for actions. We will generally clean this up and remove it when normalizing, but we don't currently normalize a script before saving it, so it isn't caught if you just paste this and save.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes Copy / Paste not working with Sequence inside Scripts #27513
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[arturpragacz]

As an alternative we could consider migrating scripts to use actions at the top level, just as automations already do.

[karwosts]

As an alternative we could consider migrating scripts to use actions at the top level, just as automations already do.

Even if you do that, and then treat a sequence paste as always a building-block, there is still a large collection of scripts out there with the legacy syntax, and pasting those would no longer behave as originally intended. Not necessarily a deal breaker, but just something to consider.