When using the markdown shortcuts plugin with custom transformers, if a transformer's replace function returns false to cancel the transformation, the leading node of the matching node is still removed from the document. This happens because leadingNode.remove() is called before checking the return value of the replace function in this line

This seems unintended since it doesn't respect the documentation of the replace function: @return return false to cancel the transform, even though the regex matched. Lexical will then search for the next transformer.

Fixing this would enable writing transformers that do not replace the content even if they match, under certain conditions. For example preventing turning headers into numbered lists if you type 1. Header, like Notion and other popular editors do.

Lexical version: v0.31.2

Steps To Reproduce

1. Create a markdown transformer that returns false from its replace function
2. Type a markdown shortcut that would trigger the transformer
3. The document is modified despite the transformation being cancelled

The current behaviour

The leading node gets removed even if the replace is cancelled.

The expected behavior

Returning false from the replace function should cancel the transform and not remove the nodes.

Impact of fix

This issue prevents applying markdown transformers conditionally. For example, if you don't want to transform headings into numbered lists which is a common use case.

Let me know what you think. Happy to put up a PR.