Formatting documents with svelte-language-server always marks them as modified in nvim

[MonaMayrhofer]

Describe the bug
When using svelte-language-server in conjunction with Neovim (using neovim's builtin lsp-support) running the format command marks the open buffer as modified, even when nothing hat to be changed. This is particularly annoying when running format as an autocommand on save, as vim prevents you from gracefully closing modified buffers. Aka: Before closing a file, the file has to be written, but after a write, it is automatically marked as unsaved again.

This behaviour does not occur in VS-Code, therefore I'm not quite sure if this language server is actually the bad guy here, but I haven't noticed such a behaviour with other language servers - so maybe you guys can hint me into the right direction if svelte-lsp is not the villain here.

To Reproduce
Steps to reproduce the behavior:

• Using neovim v0.6.0 or higher
• Install neovim/nvim-lspconfig using paq or a similar package manager.
• Setup svelte-lsp using require('lspconfig')["svelte"].setup{}
• Open a (empty) .svelte file.
• :lua vim.lsp.buf.formatting()
• Notice that even though the file contents have not changed, nvim marked it as modified (:q will yield a warning)

Expected behavior
A call to the LSP's formatting logic via :lua vim.lsp.buf.formatting() should either modify the buffer with the results from the formatter OR if no modification is necessary leave the buffer untouched and not mark it as modified.

System (please complete the following information):

• OS: Archlinux
• IDE: NVIM v0.6.0-dev+61-g6f48c018b
• Plugin/Package: nvim-lspconfig (which calls svelteserver --stdio)

Additional context
I have not dug too deep inside the code, but maybe this part

const formattedCode = prettier.format(document.getText(), {
            ...config,
            plugins: getSveltePlugin(),
            parser: 'svelte' as any
});

return [
            TextEdit.replace(
                Range.create(document.positionAt(0), document.positionAt(document.getTextLength())),
                formattedCode
            )
];

is the problem, as it yields a TextEdit.replace without regard to whether anything has actually changed.

[dummdidumm]

That snippet is probably the culprit, we should return null here if nothing changed. My guess is that VS Code checks the string, i.e. handles this case for us, whereas neovim does not.

[dummdidumm]

Fix is released, please let me know if it worked.

[MonaMayrhofer]

Whoa! I really didn't expect such a quick response for such a niche problem! Things are working as expected now! Thousand thanks to you.