When only using block level images, insertcontent-invalid-insertion-position in console on paste of HTML

[Joel-Levi]

📝 Provide detailed reproduction steps (if any)

Reproduction repo

1. Have an editor with only the folowing plugins: [ Essentials, ImageBlock, Paragraph, Undo ]

2. Paste html looking like: <img><br><img> or <img>CK<img>

Clipboard contents on moment of pasting:

<meta http-equiv="content-type" content="text/html; charset=utf-8"><img src="http://127.0.0.1:5501/sample/repro.png"> <br> <img src="http://127.0.0.1:5501/sample/repro.png">%

✔️ Expected result

HTML gets pasted and is rendered properly

❌ Actual result

nothing is pasted, insertcontent-invalid-insertion-position error in the console, coming from here : https://github.com/ckeditor/ckeditor5/blob/04a8c63bdad639792727275a0e30832869c7067f/packages/ckeditor5-engine/src/model/utils/insertcontent.ts#L362

❓ Possible solution

unfocusing the editor after this reproduction fixes the rendering somehow.

📃 Other details

• Browser: Latest Chrome, Latest Firefox
• OS: Linux Ubuntu
• First affected CKEditor version: ?
• Installed CKEditor plugins: [ Essentials, ImageBlock, Paragraph, Undo ]

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[Dumluregn]

Hello, thank you for reporting and providing a sample repo. Unfortunately, I wasn't able to reproduce the issue - see the recording below.

https://github.com/ckeditor/ckeditor5/assets/10883184/ba248810-9c73-4ee8-9712-2caf27ec0b52

It would be best if you are able to also send a recording showing the exact use case, so showing the source you are copying the content from, and the editor state when you are pasting it.

[Joel-Levi]

recording.webm

I am dragging the content that is in the reproduction page into the editor. You can see nothing is rendered, until I press a button

[Dumluregn]

Thank you, I can reproduce the problem and will investigate it.

[Dumluregn]

Issue details:

1. It reproduces for any content with the following pattern: block element + non-paragraph element that needs autoparagraphing (soft break, text etc) + block element.
2. When such content is pasted/dropped into the editor, only the middle part is autoparagraphed, which later causes a positions mismatch inside https://github.com/ckeditor/ckeditor5/blob/39a77912905694a61e8da4c42dd1b36f76fde400/packages/ckeditor5-engine/src/model/utils/insertcontent.ts#L349-L368.
3. If ImageInline plugin is loaded, pasted image becomes <imageInline> instead. Then the whole content goes into an autoparagraph so the positions are correct and the issue does not occur.

I added a failing unit test and images to the imageBlock manual test for easy issue reproduction at ck/16321-invalid-insert-content branch.