[WP6.5] Top Toolbar: Toggle does not work as expected when title or block is selected

[t-hamano]

Description

The top block toolbar is expected to open the closed block toolbar when a new block is selected, as mentioned in the comments below.

https://github.com/WordPress/gutenberg/blob/9a8984afb45df1635b2a5048b33e8ab9f95bff27/packages/edit-post/src/components/header/index.js#L93

However, the following two problems occur in the post editor.

• Selecting a new block does not open the block toolbar
• Vertical separator appears in the header when clicking title with block toolbar open

This issue does not occur in WP6.4, so I believe it is a regression occurring in WP6.5 or the latest Gutenberg.

Step-by-step reproduction instructions

• Open the post editor and insert multiple paragraph blocks.
• Enable "Top tooplbar".
• Select one paragraph block. The block toolbar should now be open.
• Close the block toolbar.
• Select another paragraph block.
• ❌ The block toolbar should not open.
• With the block toolbar open, click the post title.
• ❌ A vertical separator should appear in the header.

Screenshots, screen recording, code snippet

53316e3536999f9ad957311e8b497020.mp4

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[Mamaduka]

Can you reproduce this on the latest Gutenberg trunk?

I can reproduce it. I think there's an bug with sync logic.

[t-hamano]

Can you reproduce this on the latest Gutenberg trunk?

Yes. I think that the cause is that the logic is slightly different between the post editor and the site editor, and I'm investigating...

Post Editor:

gutenberg/packages/edit-post/src/components/header/index.js

Lines 92 to 97 in efe7d2e

	useEffect( () => {
	// If we have a new block selection, show the block tools
	if ( hasBlockSelection ) {
	setIsBlockToolsCollapsed( false );
	}
	}, [ hasBlockSelection ] );

Site Editor:

gutenberg/packages/edit-site/src/components/header-edit-mode/index.js

Lines 95 to 100 in efe7d2e

	useEffect( () => {
	// If we have a new block selection, show the block tools
	if ( blockSelectionStart ) {
	setIsBlockToolsCollapsed( false );
	}
	}, [ blockSelectionStart ] );

[Mamaduka]

I think I've a solution, will push PR shortly.