Repository: ianstormtaylor/slate
File: packages/slate/src/transforms-text/insert-fragment.ts (TypeScript)

Code before:
      voids,
    })

    if (inlineElementMatch) {
      const [, inlinePath] = inlineElementMatch

      if (Editor.isEnd(editor, at, inlinePath)) {
        const after = Editor.after(editor, inlinePath)!
        at = after
      } else if (Editor.isStart(editor, at, inlinePath)) {
        const before = Editor.before(editor, inlinePath)!
        at = before
      }
    }

    const blockMatch = Editor.above(editor, {
      match: n => Element.isElement(n) && Editor.isBlock(editor, n),
      at,
      voids,
    })!
    const [, blockPath] = blockMatch
    const isBlockStart = Editor.isStart(editor, at, blockPath)
    const isBlockEnd = Editor.isEnd(editor, at, blockPath)
    const isBlockEmpty = isBlockStart && isBlockEnd
    const mergeStart = !isBlockStart || (isBlockStart && isBlockEnd)
    const mergeEnd = !isBlockEnd
    const [, firstPath] = Node.first({ children: fragment }, [])
    const [, lastPath] = Node.last({ children: fragment }, [])

    const matches: NodeEntry[] = []
    const matcher = ([n, p]: NodeEntry) => {
      const isRoot = p.length === 0
      if (isRoot) {
        return false
      }

      if (isBlockEmpty) {
        return true
      }

      if (
        mergeStart &&
        Path.isAncestor(p, firstPath) &&
        Element.isElement(n) &&
        !editor.isVoid(n) &&
        !editor.isInline(n)
      ) {
        return false
      }

      if (

Review comment (refactor):
**Explanation of my decision here:**
I'm not sure why the logic for `mergeStart` was written like this when it can be simplified to `!isBlockStart || isBlockEnd`.

In addition, the `mergeStart` and `mergeEnd` variables are unused in the case where `isBlockEmpty` (i.e. `isBlockStart && isBlockEnd`) is true. See the following truth table:

| `isBlockStart` | `isblockEnd` | `isBlockEmpty` | `mergeStart`               |
| -------------- | ------------ | -------------- | -------------------------- |
| false          | false        | false          | true                       |
| false          | true         | false          | true                       |
| true           | false        | false          | false                      |
| true           | true         | true           | true (this case is unused) |

As a result, we can simplify `mergeStart` to just `!isBlockStart` without affecting the functionality at all. Then we get the much more intuitive:

```ts
const mergeStart = !isBlockStart
const mergeEnd = !isBlockEnd
```

I've removed these variables and included `!isBlockStart` and `!isBlockEnd` directly in the conditions where they were used, along with comments to explain more clearly what they're for.

Code after:
      voids,
    })

    if (inlineElementMatch) {
      const [, inlinePath] = inlineElementMatch

      if (Editor.isEnd(editor, at, inlinePath)) {
        const after = Editor.after(editor, inlinePath)!
        at = after
      } else if (Editor.isStart(editor, at, inlinePath)) {
        const before = Editor.before(editor, inlinePath)!
        at = before
      }
    }

    const blockMatch = Editor.above(editor, {
      match: n => Element.isElement(n) && Editor.isBlock(editor, n),
      at,
      voids,
    })!
    const [, blockPath] = blockMatch
    const isBlockStart = Editor.isStart(editor, at, blockPath)
    const isBlockEnd = Editor.isEnd(editor, at, blockPath)
    const isBlockEmpty = isBlockStart && isBlockEnd
    const [, firstLeafPath] = Node.first({ children: fragment }, [])
    const [, lastLeafPath] = Node.last({ children: fragment }, [])

    // For each node in the fragment, determine what level of wrapping should
    // be kept. At minimum, all text nodes will be inserted, but if
    // `shouldInsert` returns true for some ancestor of a particular text node,
    // then the entire ancestor will be inserted rather than inserting the text
    // nodes individually.
    const shouldInsert = ([n, p]: NodeEntry) => {
      const isRoot = p.length === 0
      if (isRoot) {
        return false
      }

      // If the destination block is empty, insert all top-level blocks of the
      // fragment.
      if (isBlockEmpty) {
        return true
      }

      // Unless we're at the start of the destination block, unwrap any
      // non-void blocks that contain the first leaf node in the fragment.
      if (
        !isBlockStart &&
        Path.isAncestor(p, firstLeafPath) &&
        Element.isElement(n) &&
        !editor.isVoid(n) &&