Merge pull request rust/rustc-dev-guide#2814 from erfanio/main

Update neovim instructions for neovim 0.11+

Author: reddevilmidzy

src/building/suggested.md

@@ -144,77 +144,82 @@ If running `./x check` on save is inconvenient, in VS Code you can use a [Build
 
 ### Neovim
 
-For Neovim users, there are a few options.
-The easiest way is by using [neoconf.nvim](https://github.com/folke/neoconf.nvim/),
-which allows for project-local configuration files with the native LSP.
-The steps for how to use it are below.
-Note that they require rust-analyzer to already be configured with Neovim.
-Steps for this can be [found here](https://rust-analyzer.github.io/manual.html#nvim-lsp).
+For Neovim users, there are a few options:
+
+1. The easiest way is using [neoconf.nvim][neoconf.nvim] but it uses the
+   deprecated `require('lspconfig')` API which displays a warning on neovim 0.11+.
+2. Using `coc.nvim` is another option but it requires node.js to be installed.
+3. Using a custom script to load rust-analyzer settings.
+
+#### neoconf.nvim
+
+[neoconf.nvim][neoconf.nvim] allows for project-local configuration
+files with the native LSP. The steps for how to use it are below. Note that they require
+rust-analyzer to already be configured with Neovim. Steps for this can be
+[found here][r-a nvim lsp].
 
 1. First install the plugin.
    This can be done by following the steps in the README.
 2. Run `./x setup editor`, and select `vscode` to create a `.vscode/settings.json` file.
    `neoconf` is able to read and update
    rust-analyzer settings automatically when the project is opened when this file is detected.
 
+#### coc.nvim
+
 If you're using `coc.nvim`, you can run `./x setup editor` and select `vim` to
 create a `.vim/coc-settings.json`.
 The settings can be edited with `:CocLocalConfig`.
 The recommended settings live at [`src/etc/rust_analyzer_settings.json`].
 
-Another way is without a plugin, and creating your own logic in your configuration.
-The following code will work for any checkout of rust-lang/rust (newer than February 2025):
+#### Custom LSP settings
+
+If you're running neovim 0.11+, you can configure rust-analyzer with just
+[nvim-lspconfig](https://github.com/neovim/nvim-lspconfig) and a custom script.
+
+1. Make sure [rust-analyzer LSP][r-a nvim lsp] is set up
+2. Create `$HOME/.config/nvim/after/plugged/rust_analyzer.lua` with the following content:
 
 ```lua
-local function expand_config_variables(option)
-    local var_placeholders = {
-        ['${workspaceFolder}'] = function(_)
-            return vim.lsp.buf.list_workspace_folders()[1]
-        end,
-    }
-
-    if type(option) == "table" then
-        local mt = getmetatable(option)
-        local result = {}
-        for k, v in pairs(option) do
-            result[expand_config_variables(k)] = expand_config_variables(v)
+-- Capture the default functions from nvim-lspconfig/lsp/rust_analyzer.lua before overriding it.
+-- This file is in after/plugin to guarantee nvim-lspconfig has been initialised already.
+local default_root_dir = vim.lsp.config["rust_analyzer"].root_dir
+local default_before_init = vim.lsp.config["rust_analyzer"].before_init
+
+vim.lsp.config("rust_analyzer", {
+    cmd = { "rust-analyzer" },
+    filetypes = { "rust" },
+    -- To support rust-lang/rust, we need to detect when we're in the rust repo and use the git root
+    -- instead of cargo project root.
+    root_dir = function(bufnr, on_dir)
+        local git_root = vim.fs.root(bufnr, { ".git" })
+        if git_root then
+            if vim.uv.fs_stat(vim.fs.joinpath(git_root, "src/etc/rust_analyzer_zed.json")) then
+                on_dir(git_root)
+                return
+            end
         end
-        return setmetatable(result, mt)
-    end
-    if type(option) ~= "string" then
-        return option
-    end
-    local ret = option
-    for key, fn in pairs(var_placeholders) do
-        ret = ret:gsub(key, fn)
-    end
-    return ret
-end
-lspconfig.rust_analyzer.setup {
-    root_dir = function()
-        local default = lspconfig.rust_analyzer.config_def.default_config.root_dir()
-        -- the default root detection uses the cargo workspace root.
-        -- but for rust-lang/rust, the standard library is in its own workspace.
-        -- use the git root instead.
-        local compiler_config = vim.fs.joinpath(default, "../src/bootstrap/defaults/config.compiler.toml")
-        if vim.fs.basename(default) == "library" and vim.uv.fs_stat(compiler_config) then
-            return vim.fs.dirname(default)
-        end
-        return default
+        -- For anything that doesn't match rust-lang/rust, fallback to default root_dir
+        default_root_dir(bufnr, on_dir)
     end,
-    on_init = function(client)
-        local path = client.workspace_folders[1].name
-        local config = vim.fs.joinpath(path, "src/etc/rust_analyzer_zed.json")
-        if vim.uv.fs_stat(config) then
-            -- load rust-lang/rust settings
-            local file = io.open(config)
-            local json = vim.json.decode(file:read("*a"))
-            client.config.settings["rust-analyzer"] = expand_config_variables(json.lsp["rust-analyzer"].initialization_options)
-            client.notify("workspace/didChangeConfiguration", { settings = client.config.settings })
+    before_init = function(init_params, config)
+        -- When inside rust-lang/rust, we need to use the special rust-analyzer settings.
+        local settings = vim.fs.joinpath(config.root_dir, "src/etc/rust_analyzer_zed.json")
+        if vim.uv.fs_stat(settings) then
+            local file = io.open(settings)
+            -- nvim 0.12+ supports comments otherwise you'll need content:gsub("//[^\n]*", "").
+            local json = vim.json.decode(file:read("*a"), { skip_comments = true })
+            file:close()
+            config.settings["rust-analyzer"] = vim.tbl_deep_extend(
+                "force", -- Overwrite with the special settings when there is a conflict.
+                config.settings["rust-analyzer"] or {},
+                json.lsp["rust-analyzer"].initialization_options
+            )
         end
-        return true
-    end
-}
+        default_before_init(init_params, config)
+    end,
+})
+
+vim.lsp.enable("rust_analyzer")
 ```
 
 If you would like to use the build task that is described above, you may either
@@ -223,6 +228,9 @@ make your own command in your config, or you can install a plugin such as
 files](https://github.com/stevearc/overseer.nvim/blob/master/doc/guides.md#vs-code-tasks),
 and follow the same instructions as above.
 
+[neoconf.nvim]: https://github.com/folke/neoconf.nvim/
+[r-a nvim lsp]: https://rust-analyzer.github.io/book/other_editors.html#nvim-lsp
+
 ### Emacs
 
 Emacs provides support for rust-analyzer with project-local configuration