[Gutenberg] Avoid sending HTML to the editor when closing

[fluiddot]

Sending the HTML when closing the editor was causing the editor to recreate all blocks. Some of these blocks might be executing logic during their initialization that would be affected by the editor closing process. This in combination with destroying/deallocating the editor and the libraries used (like Reanimated), might be the cause of the following issues:

• Crash when opening and closing the editor: C++ Exception: NSt3__112system_errorE #20499
• EXC_BREAKPOINT: managedObjectContext #20647
• Drag and drop blocks: Crashes on iOS related to JSI WordPress/gutenberg#41686

I couldn't verify the above as I'm not able to reproduce them. Hence, we'd need to check in production if any of those issues are solved by this change.

To test:
This change can only be tested by incorporating logs into the React Native code.

1. Apply the following patch in the editor:

diff --git forkSrcPrefix/packages/block-library/src/paragraph/edit.native.js forkDstPrefix/packages/block-library/src/paragraph/edit.native.js
index 98662ba21c88410e8eb6291e18399ef979933f8a..f6963d277386f84097100298b75c52cd0b04b95c 100644
--- forkSrcPrefix/packages/block-library/src/paragraph/edit.native.js
+++ forkDstPrefix/packages/block-library/src/paragraph/edit.native.js
@@ -9,7 +9,7 @@ import {
 	RichText,
 	store as blockEditorStore,
 } from '@wordpress/block-editor';
-import { useCallback } from '@wordpress/element';
+import { useCallback, useEffect } from '@wordpress/element';
 import { useSelect } from '@wordpress/data';
 
 const name = 'core/paragraph';
@@ -25,6 +25,10 @@ function ParagraphBlock( {
 	clientId,
 	parentBlockAlignment,
 } ) {
+	useEffect( () => {
+		console.log( `Paragraph block ${ clientId } mounted` );
+		return () => console.log( `Paragraph block ${ clientId } unmounted` );
+	}, [] );
 	const isRTL = useSelect( ( select ) => {
 		return !! select( blockEditorStore ).getSettings().isRTL;
 	}, [] );

2. Build the app and connect it to your local Metro server.
3. Create a post/page.
4. Add a Paragraph block with some text.
5. Close the editor and save the post/page.
6. Open the post again.
7. Observe in the console that the message Paragraph block ${ clientId } mounted is printed.
8. Close the editor.
9. Observe in the console that the message Paragraph block ${ clientId } unmounted is NOT printed.

NOTE: Previously, when closing the editor blocks were being unmounted and mounted.

Regression Notes

1. Potential unintended areas of impact
   This change is very specific so I don't foresee any unintended areas that could be impacted.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A

3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

UI Changes testing checklist:

• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• VoiceOver.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• iPhone and iPad.
• Multi-tasking: Split view and Slide over. (iPad)

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr20657-3fb86e0
	Version	22.2
	Bundle ID	com.jetpack.alpha
	Commit	3fb86e0
	App Center Build	jetpack-installable-builds #4714

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr20657-3fb86e0
	Version	22.2
	Bundle ID	org.wordpress.alpha
	Commit	3fb86e0
	App Center Build	WPiOS - One-Offs #5685

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[fluiddot]

For reference, I noticed when testing that the React Native root component is not being unmounted when closing the editor. This behavior differs from Android where the root component is unmounted. This potential issue is not being introduced in this PR as it also happens in trunk.

UPDATE: I created this issue as a follow-up on this.

[SiobhyB]

LGTM, I went through the outlined test and also performed a quick smoke test using the Jetpack build to confirm no obvious side effects after closing a post. 👏 👏 👏