dotfiles/nvim/lsp/rust-analyzer.lua

---@brief
---
--- https://github.com/rust-lang/rust-analyzer
---
--- rust-analyzer (aka rls 2.0), a language server for Rust
---
---
--- See [docs](https://rust-analyzer.github.io/book/configuration.html) for extra settings. The settings can be used like this:
--- ```lua
--- vim.lsp.config('rust_analyzer', {
---   settings = {
---     ['rust-analyzer'] = {
---       diagnostics = {
---         enable = false;
---       }
---     }
---   }
--- })
--- ```
---
--- Note: do not set `init_options` for this LS config, it will be automatically populated by the contents of settings["rust-analyzer"] per
--- https://github.com/rust-lang/rust-analyzer/blob/eb5da56d839ae0a9e9f50774fa3eb78eb0964550/docs/dev/lsp-extensions.md?plain=1#L26.

local function reload_workspace(bufnr)
    local clients = vim.lsp.get_clients({ bufnr = bufnr, name = "rust_analyzer" })
    for _, client in ipairs(clients) do
        vim.notify("Reloading Cargo Workspace")
        ---@diagnostic disable-next-line:param-type-mismatch
        client:request("rust-analyzer/reloadWorkspace", nil, function(err)
            if err then
                error(tostring(err))
            end
            vim.notify("Cargo workspace reloaded")
        end, 0)
    end
end

local function user_sysroot_src()
    return vim.tbl_get(vim.lsp.config["rust_analyzer"], "settings", "rust-analyzer", "cargo", "sysrootSrc")
end

local function default_sysroot_src()
    local sysroot = vim.tbl_get(vim.lsp.config["rust_analyzer"], "settings", "rust-analyzer", "cargo", "sysroot")
    if not sysroot then
        local rustc = os.getenv("RUSTC") or "rustc"
        local result = vim.system({ rustc, "--print", "sysroot" }, { text = true }):wait()

        local stdout = result.stdout
        if result.code == 0 and stdout then
            if string.sub(stdout, #stdout) == "\n" then
                if #stdout > 1 then
                    sysroot = string.sub(stdout, 1, #stdout - 1)
                else
                    sysroot = ""
                end
            else
                sysroot = stdout
            end
        end
    end

    return sysroot and vim.fs.joinpath(sysroot, "lib/rustlib/src/rust/library") or nil
end

local function is_library(fname)
    local user_home = vim.fs.normalize(vim.env.HOME)
    local cargo_home = os.getenv("CARGO_HOME") or user_home .. "/.cargo"
    local registry = cargo_home .. "/registry/src"
    local git_registry = cargo_home .. "/git/checkouts"

    local rustup_home = os.getenv("RUSTUP_HOME") or user_home .. "/.rustup"
    local toolchains = rustup_home .. "/toolchains"

    local sysroot_src = user_sysroot_src() or default_sysroot_src()

    for _, item in ipairs({ toolchains, registry, git_registry, sysroot_src }) do
        if item and vim.fs.relpath(item, fname) then
            local clients = vim.lsp.get_clients({ name = "rust_analyzer" })
            return #clients > 0 and clients[#clients].config.root_dir or nil
        end
    end
end

---@type vim.lsp.Config
return {
    cmd = { "rust-analyzer" },
    filetypes = { "rust" },
    root_dir = function(bufnr, on_dir)
        local fname = vim.api.nvim_buf_get_name(bufnr)
        local reused_dir = is_library(fname)
        if reused_dir then
            on_dir(reused_dir)
            return
        end

        local cargo_crate_dir = vim.fs.root(fname, { "Cargo.toml" })
        local cargo_workspace_root

        if cargo_crate_dir == nil then
            on_dir(
                vim.fs.root(fname, { "rust-project.json" })
                    or vim.fs.dirname(vim.fs.find(".git", { path = fname, upward = true })[1])
            )
            return
        end

        local cmd = {
            "cargo",
            "metadata",
            "--no-deps",
            "--format-version",
            "1",
            "--manifest-path",
            cargo_crate_dir .. "/Cargo.toml",
        }

        vim.system(cmd, { text = true }, function(output)
            if output.code == 0 then
                if output.stdout then
                    local result = vim.json.decode(output.stdout)
                    if result["workspace_root"] then
                        cargo_workspace_root = vim.fs.normalize(result["workspace_root"])
                    end
                end

                on_dir(cargo_workspace_root or cargo_crate_dir)
            else
                vim.schedule(function()
                    vim.notify(
                        ("[rust_analyzer] cmd failed with code %d: %s\n%s"):format(output.code, cmd, output.stderr)
                    )
                end)
            end
        end)
    end,
    capabilities = {
        experimental = {
            serverStatusNotification = true,
            commands = {
                commands = {
                    "rust-analyzer.showReferences",
                    "rust-analyzer.runSingle",
                    "rust-analyzer.debugSingle",
                },
            },
        },
    },
    ---@type lspconfig.settings.rust_analyzer
    settings = {
        ["rust-analyzer"] = {
            lens = {
                debug = { enable = true },
                enable = true,
                implementations = { enable = true },
                references = {
                    adt = { enable = true },
                    enumVariant = { enable = true },
                    method = { enable = true },
                    trait = { enable = true },
                },
                run = { enable = true },
                updateTest = { enable = true },
            },
        },
    },
    before_init = function(init_params, config)
        -- See https://github.com/rust-lang/rust-analyzer/blob/eb5da56d839ae0a9e9f50774fa3eb78eb0964550/docs/dev/lsp-extensions.md?plain=1#L26
        if config.settings and config.settings["rust-analyzer"] then
            init_params.initializationOptions = config.settings["rust-analyzer"]
        end
        ---@param command table{ title: string, command: string, arguments: any[] }
        vim.lsp.commands["rust-analyzer.runSingle"] = function(command)
            local r = command.arguments[1]
            local cmd = { "cargo", unpack(r.args.cargoArgs) }
            if r.args.executableArgs and #r.args.executableArgs > 0 then
                vim.list_extend(cmd, { "--", unpack(r.args.executableArgs) })
            end

            local proc = vim.system(cmd, { cwd = r.args.cwd, env = r.args.environment })

            local result = proc:wait()

            if result.code == 0 then
                vim.notify(result.stdout, vim.log.levels.INFO)
            else
                vim.notify(result.stderr, vim.log.levels.ERROR)
            end
        end
    end,
    on_attach = function(_, bufnr)
        vim.api.nvim_buf_create_user_command(bufnr, "LspCargoReload", function()
            reload_workspace(bufnr)
        end, { desc = "Reload current cargo workspace" })
    end,
}