Plate collapses code_line's into a single code_line

[cloverich]

Plate's code block plugin supplies a code_line block type which we re-implement in a basic fashion. I believe this is meant to exist for each line of code within a code_block. However, even though the mdast-to-slate transformer creates these (seemingly correctly), on the first edit within the code lock Plate will collapse all of them into a single code_line.

While I am not 100% positive this is incorrect, I believe it is, and I belive it is related to a few other issues:

• Unindenting code (shift+tab) does not work once the code_lines are reduced to a single code_line
• Copy / paste (esp. if in middle of code) has all sorts of odd behavior

I dug for a while but don't understand enough about Plate's mechanics to even get a break point into the right spot, to understand which Plate plugin / component is behaving unexpected. My best guess is it has to do with Prism and specifically packages/code-block/src/client/decorateCodeLine.ts:

// comes from Slate DOM
const codeBlock = getParentNode<TCodeBlockElement>(editor, path);

// later, is normalized
let langName = codeBlock[0].lang ?? '';

// Prism applied
const tokens = tokenize(text, lang);

// Serialized to ranges with token types applied:
    for (const element of tokens) {
      if (element instanceof Token) {
        ranges.push({
          [ELEMENT_CODE_SYNTAX]: true,
          anchor: { offset, path },
          focus: { offset: offset + element.length, path },
          tokenType: element.type,
        });
      }

      offset += element.length;
    }

// return ranges