New list plugin doesn't convert subsequent lists with a different type properly (aka resetting numbering, splitting lists)

[mlewand]

📝 Provide detailed reproduction steps (if any)

For context this is a simplified markup produced by MS Word.

1. Copy following HTML to your clipboard:

<p style="margin-top: 0px; margin-bottom: 0px; line-height: 1">foo</p>

<p style="margin-top: 0px; margin-bottom: 0px; margin-left: 24px; line-height: 1">&nbsp;</p>
<ol style="list-style-type: decimal">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
</ol>

<p style="margin-top: 0px; margin-bottom: 10.67px; margin-left: 24px; line-height: 1.05">&nbsp;</p>
<ol style="list-style-type: lower-latin">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
</ol>
<ol start="2" style="list-style-type: decimal">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">Decimal list item again</p>
    </li>
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">Decimal list item again
        </p>
    </li>
</ol>

<p style="margin-top: 0px; margin-bottom: 10.67px; margin-left: 48px; line-height: 1.05">&nbsp;</p>
<ol style="list-style-type: lower-latin">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
</ol>
<ul style="list-style-type: disc">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar</p>
    </li>
</ul>
<ol start="3" style="list-style-type: lower-latin">
    <li>

        <p style="margin-top: 0px; margin-bottom: 10.67px; line-height: 1.05">foobar
        </p>
    </li>
</ol>

1. Open a demo that has new list (a.k.a. document list) implementation in it. Import from Word guide is a good example.
2. Open js dev console.
3. Execute editor.setData( `<copiedMarkupHere>` ).

✔️ Expected result

List with two "Decimal list item again" items should be a numbered list.

❌ Actual result

List goes on as alphanum list.

---

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[Reinmar]

There's a chance we're running here into a limitation of the current implementation – that it does not allow having two subsequent lists of the same type.

@niegowski or @arkflpc, could you confirm that I'm right? Or perhaps this is indeed a bug (as opposed to a missing feature)?

[niegowski]

There's a chance we're running here into a limitation of the current implementation – that it does not allow having two subsequent lists of the same type.

You are right. We even implemented a post-fixer to make sure this would not break in RTC:

ckeditor5/packages/ckeditor5-list/src/documentlistproperties/documentlistpropertiesediting.js

Lines 150 to 151 in 13d98de

	// Make sure that all items in a single list (items at the same level & listType) have the same properties.
	documentListEditing.on( 'postFixer', ( evt, { listNodes, writer } ) => {

I could imagine a case where one user is modifying a style of the list and some other user is at the same time adding a new list item. 

This probably could be someday resolved by adding listId attribute to mark strict boundaries for lists, but currently, it's a missing feature.

[jacekbogdanski]

Just theoretically, how feasible would be that fix if IFW would mark lists with an additional attribute? Like a unique ID or something, so it's possible to distinguish different lists? Would that help?

[niegowski]

Just theoretically, how feasible would be that fix if IFW would mark lists with an additional attribute? Like a unique ID or something, so it's possible to distinguish different lists? Would that help?

It's not the input problem, it's internally stored in the model (in an input-compatible way) and fixed by the post-fixer.

[Reinmar]

Very old DUP of this ticket: #3000.

[Witoso]

Scope

1. Only for DocumentList plugin.
2. Requires a new docs page / section.

Enablement

New plugin that is added by the user.

Behaviour

1. Always show two or more separate lists when we have two or more separate lists in the data.
2. List separator - create an element in the model (not visible, margins will be probably larger) - to explore.
3. Check the behavior for backspace and forward delete (problems may appear).

Two ul’s next to each other:

<ul>
	<li>LOREM</li>
	<li>IPSUM</li>
</ul>
<ul>
	<li>LOREM</li>
	<li>IPSUM</li>
</ul>

Outcome: This should not be merged.

---

Two ul’s next to each other, different styles (only list-style-type: or more styles?):

<ul style="list-style-type: square;">
	<li>LOREM</li>
	<li>IPSUM</li>
</ul>
<ul style="list-style-type: disc;">
	<li>LOREM</li>
	<li>IPSUM</li>
</ul>

Outcome: This should not be merged.

ol's

Two ol’s next to each other:

<ol>
	<li>LOREM</li>
	<li>IPSUM</li>
</ol>
<ol>
	<li>LOREM</li>
	<li>IPSUM</li>
</ol>

Outcome: This should not be merged.

---

Two ol’s next to each other, different styles (only list-style-type: or more styles?).
Probably not relevant as it will be handled by the case above anyway.

<ol>
	<li>LOREM</li>
	<li>IPSUM</li>
</ol>
<ol style="list-style-type:decimal-leading-zero;">
	<li>LOREM</li>
	<li>IPSUM</li>
</ol>

Outcome: This should not be merged.

Real life examples

• Support adjacent lists (splitting, resetting numbering) #13945 (comment)
• Support adjacent lists (splitting, resetting numbering) #13945 (comment)