Add nvim-dap with ruby/debug adapter

.config/nvim/lua/config/keymaps.lua

@@ -81,6 +81,31 @@ vim.keymap.set(
 vim.keymap.set("n", "<leader>xL", "<cmd>Trouble loclist toggle<cr>", { desc = "Location List (Trouble)" })
 vim.keymap.set("n", "<leader>xQ", "<cmd>Trouble qflist toggle<cr>", { desc = "Quickfix List (Trouble)" })
 
+-- DAP (debugging)
+vim.keymap.set("n", "<leader>db", function() require("dap").toggle_breakpoint() end, { desc = "Toggle breakpoint" })
+vim.keymap.set("n", "<leader>dc", function() require("dap").continue() end, { desc = "Continue / attach" })
+vim.keymap.set("n", "<leader>dn", function() require("dap").step_over() end, { desc = "Step over" })
+vim.keymap.set("n", "<leader>di", function() require("dap").step_into() end, { desc = "Step into" })
+vim.keymap.set("n", "<leader>do", function() require("dap").step_out() end, { desc = "Step out" })
+vim.keymap.set("n", "<leader>dq", function() require("dap").terminate() end, { desc = "Terminate session" })
+vim.keymap.set("n", "<leader>du", function() require("dapui").toggle() end, { desc = "Toggle DAP UI" })
+vim.keymap.set("n", "<leader>dr", function() require("dap").repl.toggle() end, { desc = "Toggle REPL" })
+-- Run RSpec under the debugger — skips the picker, binding.b breaks into dap-ui
+vim.keymap.set("n", "<leader>ds", function()
+	require("dap").run({
+		type = "ruby", request = "launch",
+		name = "RSpec (current file)",
+		command = "rspec", args = { vim.fn.expand("%:p") },
+	})
+end, { desc = "Debug: RSpec current file" })
+vim.keymap.set("n", "<leader>dl", function()
+	require("dap").run({
+		type = "ruby", request = "launch",
+		name = "RSpec (current line)",
+		command = "rspec", args = { vim.fn.expand("%:p") .. ":" .. vim.fn.line(".") },
+	})
+end, { desc = "Debug: RSpec current line" })
+
 -- LazyGit
 vim.keymap.set("n", "<leader>lg", "<cmd>LazyGit<cr>", { desc = "LazyGit" })
 

.config/nvim/lua/config/options.lua

@@ -19,3 +19,7 @@ vim.opt.conceallevel = 0
 
 -- Window options
 vim.wo.wrap = true
+
+-- Load per-project .nvim.lua files (used for DAP launch configs, etc.)
+vim.opt.exrc = true
+vim.opt.secure = true

.config/nvim/lua/config/plugins/dap.lua

@@ -0,0 +1,83 @@
+return {
+	{
+		"mfussenegger/nvim-dap",
+		dependencies = {
+			{ "rcarriga/nvim-dap-ui", dependencies = { "nvim-neotest/nvim-nio" } },
+		},
+		config = function()
+			local dap = require("dap")
+			local dapui = require("dapui")
+
+			dapui.setup()
+
+			-- Ruby adapter.
+			--
+			-- "attach" mode: connect to an already-running rdbg TCP server.
+			--   Used for Rails server (started externally with RUBY_DEBUG_OPEN=1)
+			--   and for Vagrant+Docker (port forwarded to localhost).
+			--
+			-- "launch" mode: rdbg starts the process as a child.
+			--   rdbg opens a TCP server, pauses before running any code, and waits
+			--   for nvim-dap to connect and register breakpoints. Once that handshake
+			--   completes, the "entry" stopped event fires — we auto-continue past it
+			--   (see listener below) so execution runs straight to your breakpoint.
+			--   cwd is resolved by finding the Gemfile so bundle exec works from any
+			--   subdirectory.
+			dap.adapters.ruby = function(callback, config)
+				if config.request == "attach" then
+					callback({
+						type = "server",
+						host = config.host or "127.0.0.1",
+						port = config.port or 12345,
+					})
+				else
+					local gemfile = vim.fn.findfile("Gemfile", ".;")
+					local cwd = gemfile ~= "" and vim.fn.fnamemodify(gemfile, ":p:h") or vim.fn.getcwd()
+					callback({
+						type = "server",
+						host = "127.0.0.1",
+						port = config.port or 12345,
+						executable = {
+							command = "bundle",
+							args = {
+								"exec", "rdbg",
+								"--open", "--port", tostring(config.port or 12345),
+								"-c", "--", config.command or "ruby",
+								unpack(config.args or {}),
+							},
+							cwd = cwd,
+						},
+					})
+				end
+			end
+
+			-- For a running Rails server, start it with:
+			--   RUBY_DEBUG_OPEN=1 RUBY_DEBUG_PORT=12345 RUBY_DEBUG_HOST=127.0.0.1 bundle exec rails s
+			-- then <leader>dc → "Attach". For Vagrant projects, override in .nvim.lua.
+			-- For RSpec use <leader>ds (file) or <leader>dl (line) — skips this picker.
+			dap.configurations.ruby = {
+				{
+					type = "ruby",
+					name = "Attach",
+					request = "attach",
+					port = 12345,
+				},
+			}
+
+			-- Auto-open dap-ui when a session initialises.
+			-- dap-ui stays open after the session ends so you can inspect the final
+			-- state — close it manually with <leader>du.
+			dap.listeners.after.event_initialized["dapui"] = dapui.open
+
+			-- In launch mode rdbg pauses at the program entry point before running
+			-- any code, ensuring nvim-dap has registered all breakpoints first. This
+			-- listener auto-continues past that initial pause so <leader>ds is one
+			-- keypress — execution runs straight to your first breakpoint.
+			dap.listeners.after.event_stopped["ruby_skip_entry"] = function(_, body)
+				if body.reason == "entry" then
+					dap.continue()
+				end
+			end
+		end,
+	},
+}