Bug: $selectAll do not set the selection `style` parameter from the anchored text node

[micaelbergeron]

Lexical version: v0.16.1

Steps To Reproduce

{"editorState":{"root":{"children":[{"children":[{"detail":0,"format":0,"mode":"normal","style":"color: #d0021b;","text":"This is red text","type":"text","version":1}],"direction":"ltr","format":"","indent":0,"type":"paragraph","version":1,"textFormat":0},{"children":[],"direction":"ltr","format":"","indent":0,"type":"paragraph","version":1,"textFormat":0}],"direction":"ltr","format":"","indent":0,"type":"root","version":1}},"lastSaved":1721138622895,"source":"Playground","version":"0.16.1"}

Notes: in my use-case, this problem comes up as I run $selectAll. We can replicate that by putting the cursor on an empty line and pressing CMD/CTRL+A.

1. Load the sample above in the playground
2. Put the cursor on the second line (empty)
3. Keyboard shortcut the select all command (CTRL+A)

Notice the selection values:

 root
> ├ (54) paragraph 
> | └ (55) text "This is red text"
> └ (56) paragraph 

 selection: range  
  ├ anchor { key: 55, offset: 0, type: text }
  └ focus { key: 56, offset: 0, type: element }

We can see here the selection is a range with the 55 text node as the anchor. This text node has a style attribute, but that isn't set in the selection.

The current behavior

Selection from $selectAll() do not load the style attribute from the anchored node. Thus starting to type will remove the styling attribute for subsequent text.

The expected behavior

Selection from $selectAll() should load the style attribute from the anchored node.

Impact of fix

I traced the fix down to the LexicalEvents.ts onSelectionChange handler.

https://github.com/facebook/lexical/blob/0fbab8fd38e8122a78cfaf1279f64e42e6ba5834/packages/lexical/src/LexicalEvents.ts#L362-L400

In this code, we can see that there is a // TODO what about styles that pinpoint this exact issue.

I will send a PR with the fix I came up with.