Unrelated meta data gets saved with default value

[ocean90]

Issue Overview

If you have a block which stores its data in post meta and also registered other post meta for REST API usage, the other post meta gets also updated with the default value.

Steps to Reproduce (for bugs)

1. Example plugin: https://gist.github.com/ocean90/7431114b689f1e0686f4f5dfa88838df
2. Activate plugin
3. Add the new block and fill the input
4. Save draft and inspect the save request
5. Notice that the meta entry includes all three meta keys while only one has been changed

Expected Behavior

Only changed meta data should get saved.

Possible Solution

I'm not sure yet if that's a limitation of the REST API and/or if Gutenberg can enhance that behaviour.

Related Issues

• Add hook for block deletion so post meta can be removed #5626

Todos

• Tests
• Documentation

[jorgefilipecosta]

Hi @ocean90,
Thank you for reporting this issue, I'm able to replicate it in my tests.
It looks like it is a rest API bug.

The rest API returns all the meta fields (available in rest) even if they have no data, which I guess is ok.
If there no changes in metadata (all fields are empty) so Gutenberg sends in the save request the same metadata it received (all fields with an empty string). In this case, the rest API correctly ignores all metadata and does not save it to the database.

If we change one field (for example using the block @ocean90 provided), Gutenberg save request contains all non-changed fields precisely as they were provided (with an empty string), and in the changed field, we set the new value. In this case, the rest API instead of ignoring all non-changed empty fields and just saving the non empty one to the database it saves both the empty fields and the new value.

[ocean90]

I don't think that this is a REST API bug but rather that Gutenberg should only send changed meta values back to the REST API.

[felixarntz]

I agree with @ocean90 in that matter. I think Gutenberg should check if the meta value is different from the initial value retrieved from the API before it passes it there.

[aduth]

Closed by #10827.