Editor crashes after pasting multi-block content over existing content in a blockquote

[Mgsy]

Is this a bug report or feature request? (choose one)

🐞 Bug report

💻 Version of CKEditor

Latest master

📋 Steps to reproduce

1. Set the following data: editor.setData( '<blockquote><p>test</p><p>test</p></blockquote>' );
2. Copy those paragraphs.
3. Press Ctrl + A.
4. Paste.

✅ Expected result

Content is pasted properly.

❎ Actual result

The editor crashes.

📃 Other details that might be useful

Error

schema.js:1156 Uncaught TypeError: Cannot read property 'getAncestors' of null
    at new me (schema.js:1156)
    at fe.on.priority (schema.js:58)
    at fe.fire (emittermixin.js:207)
    at fe.<computed> [as checkChild] (observablemixin.js:259)
    at fn._getAllowedIn (insertcontent.js:603)
    at fn._checkAndSplitToAllowedPosition (insertcontent.js:544)
    at fn._handleNode (insertcontent.js:259)
    at fn.handleNodes (insertcontent.js:185)
    at Object.callback (insertcontent.js:69)
    at xn._runPendingChanges (model.js:738)

GIF

It's a regression. I've bisected it and it looks like these changes introduced a bug - ckeditor/ckeditor5-engine@f4e4644

[pomek]

I wrote a test that reproduces the issue:

it( 'does not blow up after pasting items over block-quote', () => {
	setModelData( model,
		'[<blockQuote>' +
			'<paragraph>Foo</paragraph>' +
			'<paragraph>Bar</paragraph>' +
		'</blockQuote>]'
	);

	console.log( getModelData( model ) );

	pasteHtml( editor, '<p>FooBar</p>' );

	console.log( getModelData( model ) );
} );

function pasteHtml( editor, html ) {
	editor.editing.view.document.fire( 'paste', {
		dataTransfer: createDataTransfer( { 'text/html': html } ),
		preventDefault() {
		}
	} );
}

function createDataTransfer( data ) {
	return {
		getData( type ) {
			return data[ type ];
		}
	};
}

And it fails (as expected):

CKEditorError: model-position-path-incorrect: The position's path is incorrect. Read more: https://ckeditor.com/docs/ckeditor5/latest/framework/guides/support/error-codes.html#error-model-position-path-incorrect
       {"position":{"root":"main","path":[0,0,0],"stickiness":"toNext"}}

A place in the code where the error was thrown: https://github.com/ckeditor/ckeditor5-engine/blob/04fa92058a83d70c7384713cab9f462d2f1ae90f/src/model/utils/insertcontent.js#L139

And I guess, I understand why it happens. The position after removing all nodes from the editor is invalid. After switching the position to be an instance of LivePosition, the error does not occur. But it isn't a solution. That gave me an idea of what could be wrong.

Then, I decided to write one more test for the insertcontent util that does more or less the same as the previous one:

it.only( 'deletes selection with elements before inserting the content', () => {
	model.schema.register( 'p', { inheritAllFrom: '$block' } );
	model.schema.register( 'div', {
		allowWhere: '$block',
		allowContentOf: '$root'
	} );

	setData( model, '[<div><p>Foo</p><p>Bar</p></div>]' );
	const affectedRange = insertHelper( '<p>FooBar</p>' );

	expect( getData( model ) ).to.equal( '<p>FooBar</p>[]' );
	expect( stringify( root, affectedRange ) ).to.equal( '[<p>FooBar</p>]' );
} );

Unfortunately, it didn't fail as I expected. For such case, a position used to create an instance of Insertion class seems to be valid.

What am I doing wrong here?

[pomek]

Thanks to @Reinmar, we figured out what was wrong with the second test. Instead of using a short name of paragraph (p), I should use a full name of the element because the engine assumes that the element exists.

The corrected tests should look like:

it( 'deletes selection with elements before inserting the content', () => {
	model.schema.register( 'div', {
		allowWhere: '$block',
		allowContentOf: '$root'
	} );

	setData( model, '<div><paragraph>[Foo</paragraph><paragraph>Bar]</paragraph></div>' );
	const affectedRange = insertHelper( '<paragraph>FooBar</paragraph>' );

	expect( getData( model ) ).to.equal( '<paragraph>FooBar[]</paragraph>' );
	expect( stringify( root, affectedRange ) ).to.equal( '[<paragraph>FooBar</paragraph>]' );
} );

And this one, as expected, fails. Going into deep, it leads to this issue – https://github.com/ckeditor/ckeditor5-engine/issues/1722 and I'll continue posting my thoughts here.

[pomek]

Using the Title plugin, the issue is even "easier" to reproduce.

Type whatever in the title section, then select all (CTRL/CMD+A) then paste anything.

[Reinmar]

DUP of #2010. Fixed with ckeditor/ckeditor5-engine#1830.