Question: can LSP be outsourced to nvim core in >= 0.12?

[Pebkac03]

With Nvim supporting LSP natively and also having added support for color recently. Are there any LSP features left before the language server can be configured using lsp-config + nvim core without losing any functionality?

Asking since 1. Having one way to configure my LSP:s I feel would be easier in my mind, 2. I would assume it would reduce scope of this plugin?

[sidlatau]

Yes, at least partially.
Neovim core has been absorbing more LSP functionality, and textDocument/documentColor is the clearest example. For colors specifically, the answer is effectively “yes, core can own this”, at least on Neovim 0.12+, where users can rely on vim.lsp.document_color.enable() instead of plugin-managed color rendering.
That said, the full LSP integration cannot be outsourced to Neovim core + lspconfig yet without losing plugin-specific behavior. flutter-tools.nvim still provides Dart/Flutter-specific pieces that are not covered by core, for example:

• Flutter outline / widget guides
• closing labels
• custom Dart methods like dart/reanalyze and dart/textDocument/super
• Flutter-oriented project/root handling and startup behavior around dartls
  So the direction that makes sense to me is:

1. move generic features to core where Neovim already provides them well
2. keep plugin-specific Flutter/Dart functionality in this plugin
3. continue shrinking the custom LSP surface over time where it makes sense
   In practical terms, document colors look like a good candidate to move to core, but flutter-tools.nvim is not fully replaceable by plain Neovim core + lspconfig yet.

#525 adds a deprecation message for colors config.