Unregistering core/site-logo block crashes editor when editing Patterns

[MadtownLems]

Description

When using javascript to unregister the core/site-logo block, and trying to add/edit a Pattern, the editor crashes with the following error: TypeError: Cannot read properties of undefined (reading 'styleVariationSelectors')

Step-by-step reproduction instructions

Enqueue the following javascript:

wp.domReady( () => {

    // does NOT crash editing Patterns; successfully unregisters archives block
    wp.blocks.unregisterBlockType( 'core/archives' );

    // crashes editing Patterns with error:
    // TypeError: Cannot read properties of undefined (reading 'styleVariationSelectors')

	wp.blocks.unregisterBlockType( 'core/site-logo' );
	

} );

Attempt to add or edit a Pattern. The editor crashes and lets you copy the error, which is:
TypeError: Cannot read properties of undefined (reading 'styleVariationSelectors')

Screenshots, screen recording, code snippet

No response

Environment info

WP 6.6-RC-2. (I have confirmed the same behavior on 6.6-RC-1, but I am quite confident that this did not crash on the early Beta I tested, and it definitely doesn't crash on 6.5.5)
No Gutenberg Plugin

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

[t-hamano]

Thanks for the report.

I was able to reproduce this issue too. This issue does not occur in WP6.5. It does occur in WP6.6 RC2 and the latest Gutenberg.

ae49830e0d2bf1951071897345b270b6.mp4

[ndiego]

Yup, I can confirm, but this appears to be a larger issue. The Site Editor crashes when registering Image blocks as well and perhaps others. I have not tested all blocks.

wp.domReady( () => {
	// Crashes Site Editor with error:
	// wp.blocks.unregisterBlockType( 'core/site-logo' );
	wp.blocks.unregisterBlockType( 'core/image' );
} );

[ndiego]

Flagging you all since this appears to be an extensibility regression: @fabiankaegy @colorful-tones @ellatrix @vcanales

[t-hamano]

The following changes seem to fix the critical issue, but may not be ideal. Perhaps @aaronrobertshaw knows more about this part of the code?

diff --git a/packages/block-editor/src/components/global-styles/use-global-styles-output.js b/packages/block-editor/src/components/global-styles/use-global-styles-output.js
index 6756398708..41d6970d03 100644
--- a/packages/block-editor/src/components/global-styles/use-global-styles-output.js
+++ b/packages/block-editor/src/components/global-styles/use-global-styles-output.js
@@ -671,7 +671,7 @@ export const getNodesWithStyles = ( tree, blockSelectors ) => {
                                                }
                                                const variationSelector =
                                                        blockSelectors[ blockName ]
-                                                               .styleVariationSelectors?.[ variationName ];
+                                                               ?.styleVariationSelectors?.[ variationName ];
 
                                                // Process the variation's inner element styles.
                                                // This comes before the inner block styles so the

[ndiego]

The following changes seem to fix the critical issue, but may not be ideal.

🤞 this issue is just due to a missing ?.

[aaronrobertshaw]

Thanks for the ping 👍

It does look like I missed the optional chaining operator there, working under the impression the block nodes would match the available blocks.

Given that isn't the case the proposed fix is along the right lines. This issue also shows that a variation's inner blocks could also be deregistered triggering a similar error a few lines down.

I'll put together a fix in a moment.

[aaronrobertshaw]

A fix following Aki's suggestion is available in #63252.