Making Neovim a Lightweight Unreal Engine IDE: Implementing Blazing Fast Completion without LSP

#gamedev #rust #showdev #tooling

Hi everyone! I’m the creator of the UnrealDev.nvim suite, a project dedicated to turning Neovim into the ultimate IDE for Unreal Engine (UE) development.

After migrating our core logic to the Rust-based "unl-server", I've shifted focus to a major milestone: Improving the built-in completion engine.

🛠 The "Why": Moving Beyond LSP

For a long time, I relied on LSPs like clangd. However, UE development—especially on Windows—poses unique challenges:

LSP Overhead: Waiting for indexers and compilation in massive UE projects can be frustratingly slow.
The "Clang Database" Headache: Generating and maintaining .compile_commands.json or .rsp files often conflicts with standard UBT (Unreal Build Tool) workflows.

I love Neovim for its speed. It felt wrong that "heavy" IDEs like Rider were sometimes more responsive than my Neovim setup. So, I decided to build a database-driven completion engine that doesn't rely on a full LSP stack.

🚀 Performance Showcase

Take a look at the custom completion in action:

This is powered entirely by unl-server and our custom DB. It currently supports:

Standard variable declarations.
auto keyword type resolution.
UE-specific templates like TObjectPtr<T>.
*Return values of functions (e.g., Getters/Setters) — *

⚙️ How it works

When completion is triggered, the current buffer and cursor position are sent to unl-server. The server infers the class context and returns candidates via MessagePack-RPC.

I’m currently using taku25/blink-cmp-unreal, but since the core logic resides on the server, it can be adapted to other completion engines easily.