[Block] Table of Contents: Block Error when nested inside columns on Simple sites

[cuemarie]

Quick summary

When the Table of Contents block is nested inside a column, it's throwing an unexpected error in the editor: This block contains unexpected or invalid content.

This stops the block from updating to match the page.

Steps to reproduce

1. On a new page or post, add the Table of Contents block, along with a couple Heading blocks to give the TOC block something to reference.
2. Publish the page and refresh.
3. Next, add a columns block, and place the TOC block inside the Columns block.
4. Update the page, and refresh once more.

What you expected to happen

The block to not break when nested.

What actually happened

The block displays the unexpected error. Selecting Attempt Block Recovery fixes, but the issue returns the next time you load the editor.

Example

Screen.Capture.on.2022-12-07.at.16-19-04.mp4

⚠️ Impact - If the user does not select Attempt Block Recovery, the TOC block will not update to reflect new changes on the page.

Screen.Capture.on.2022-12-07.at.16-38-35.mov

Selecting ... and Resolve Shows:

From there, selecting Convert to Blocks changes the Table of Contents into a Static list, which no longer automatically updates, so it's feasible that users will end up breaking their TOC's automatic workings while trying to resolve this issue.

Context

Came up while helping this user create a page with a 2-column layout and Table of Contents blocks in their right-hand sidebar: 38414229-hc

Platform (Simple, Atomic, or both?)

Simple

Theme-specific issue?

Not Theme-Specific.

Tested on Simple, using multiple themes: Twenty Twenty, Penscratch 2

Browser, operating system and other notes

No response

Reproducibility

Consistent

Severity

Some (< 50%)

Available workarounds?

No but the platform is still usable

Workaround details

There's no alternative way to add the TOC block to a column and prevent that error from appearing. The user will need to select Attempt Block Recovery every time they update their page.

[cuemarie]

📌 SCRUBBING : RESULT

• Tested on P2: Replicated
• Tested on Simple: Replicated
• Tested on AT: Could Not Replicate
• Tested on Self-hosted: Could Not Replicate
• Replicable on Core? No

📌 FINDINGS/SCREENSHOTS/VIDEO

• I'm still able to replicate the issue above on both P2 and Simple test sites. AT and Self-Hosted do not encounter the same problem.

Example

📌 ACTIONS

• Marked as Triaged for Quality Squad review

[kathrynwp]

I've run into this bug numerous time on P2s, and it's a real issue. :) Would be awesome if anyone were able to take a look.

[Joshgrygiel]

Another report here: 40187890-hc

User's site is AT and the error is apparent after nesting numerous columns within additional columns

[aleone89]

Another report of this here: https://wordpress.com/forums/topic/error-on-blocks-in-edit-mode/?view=all

[cuemarie]

Still able to replicate this on my Simple site:

[cuemarie]

Still reproducing on simple sites, however theres not a lot of traction or user reports of this issue, so I think we can safely lower the priority on this to Normal for now.

[eduardozulian]

I confirmed we can reproduce the issue if you replace the Columns with the Media & Text block. As per the original report, this only happens on simple sites.

This was reported on 7617764-zen, which is related to a longer conversation in p58i-gz0-p2

Pinging @cuemarie in case you believe this is something we should prioritize.

[github-actions]

Support References

This comment is automatically generated. Please do not edit it.

• https://wordpress.com/forums/topic/error-on-blocks-in-edit-mode
• 7617764-zen
• 7830208-zen

[jp-imagines]

Came across this in 7830208-zd-a8c and replicated on a test site as well. In this case, the Table of Contents blocks throw the unexpected or invalid content error when nested even in just a Group block.

[cuemarie]

Hey @eduardozulian , thanks for the ping and apologies for my delayed response! While this only impacts simple sites who arrange their TOCs this way, I think the issue has the potential to be quite inconvenient for those specific folks.

This was deprioritized from High to Normal in June 2023 to align with internal Dotcom goals at the time. I'm not involved in issue prioritization anymore, but my 2 cents is that "Normal" is still the right priority level, given the low number of customer reports and workaround availability.