emacs: configure dap-mode and compile-mode

Debug Adapter Protocol (DAP) is wire protocol to communicate between a
client and debug server. This is similar to LSP, but for debuggers.

This initial configuration focuses on enabling the mode and setting the
layout for the various buffers (in this case I want the different
buffers on the right screen and keep the main part focused on the code).
I also disable some widget to use the debugger with hydra.

There's still a number of things that are incomplete when it comes to
integrate DAP and delve (the go debugger): there's no way to call
functions, to have access to the variables, etc. But this is a good
start though, to debug simple problems without relying on print
statement.

This also update the configuration for =go= so that =M-x compile=, when
editing a go file, by default will use =go build=. This is not what I
always need / want but this is a good default.

4 files changed, 71 insertions, 1 deletions

diff --git a/README.org b/README.org
index c43b4aa..2d782e2 100644
--- a/README.org
+++ b/README.org
@@ -4,6 +4,31 @@
 - keep it simple
 - configurations work the same way, everywhere
 * emacs
+** go
+*** compile
+You can compile a go binary using =M-x compile= inside a go buffer.
+*** debugging
+We need to install =dlv= first:
+#+begin_src sh
+go install github.com/go-delve/delve/cmd/dlv@latest
+#+end_src
+
+For =dap-mode= you also need to install =nodejs=. On arch you do this with
+#+begin_src sh
+sudo pacman -Syu nodejs
+#+end_src
+
+Then from emacs =M-x dap-go-set= to install the dependencies.
+
+It's unclear as to why =node= is still in the picture since it looks like =dlv= seems to support =dap= directly (see [[https://github.com/go-delve/delve/issues/1515][delve/issues/1515]]).
+
+To debug a program, you can set breakpoints where you need with =M-x dap-breakpoint-add=. To start the debugger hit =M-x dap-debug=.
+
+If the program you debug needs argument, call =M-x dap-debug-edit-template=. Add the argument(s) you need to the program and evaluate the buffer (=C-c C-e=). Next time you call the debugger, the argument(s) will be passed to the program. You can also set environment variables if you need.
+
+The binding =C-c d= will bring an hydra menu for debugging.
+
+The REPL is not brought on by default when starting a debugging session, but =M-x dap-ui-repl= will start a REPL (the position is controlled by the variable =dap-ui-buffer-configurations=).
 * Linux
 ** installed packages
 Under arch linux, you can run the following to get the list of installed packages:
diff --git a/emacs/custom/fcuny-navigation.el b/emacs/custom/fcuny-navigation.el
index de17080..1a58666 100644
--- a/emacs/custom/fcuny-navigation.el
+++ b/emacs/custom/fcuny-navigation.el
@@ -152,4 +152,12 @@
   :config
   (which-key-mode))
 
+;; treemacs is being pulled by lsp/dap mode, so let's be explicit
+;; about getting it installed, and ensure that it writes its own data
+;; in our var directory.
+(use-package treemacs
+  :ensure t
+  :custom
+  (treemacs-persist-file (expand-file-name "treemacs-persist" fcuny/path-emacs-var)))
+
 (provide 'fcuny-navigation)
diff --git a/emacs/custom/fcuny-prog.el b/emacs/custom/fcuny-prog.el
index 3cc97d9..1ca50ca 100644
--- a/emacs/custom/fcuny-prog.el
+++ b/emacs/custom/fcuny-prog.el
@@ -55,6 +55,33 @@
   :ensure t
   :commands lsp-ivy-workspace-symbol)
 
+(use-package dap-mode
+  :ensure t
+  :after (lsp-mode)
+  :bind ("C-c d" . dap-hydra)
+  :init
+  (use-package dap-go)
+  :custom
+  (dap-utils-extension-path (expand-file-name ".extension" fcuny/path-emacs-var))
+  (dap-breakpoints-file (expand-file-name "dap-breakpoints" fcuny/path-emacs-var))
+  (dap-ui-controls-mode nil)
+  (dap-ui-buffer-configurations
+   `((,dap-ui--locals-buffer       . ((side . right) (slot . 1) (window-width . 0.2)))
+     (,dap-ui--expressions-buffer  . ((side . right) (slot . 2) (window-width . 0.2)))
+     (,dap-ui--sessions-buffer     . ((side . right) (slot . 3) (window-width . 0.2)))
+     (,dap-ui--breakpoints-buffer  . ((side . right) (slot . 4) (window-width . 0.2)))
+     (,dap-ui--repl-buffer         . ((side . bottom) (slot . 1) (window-width . 0.4)))
+     (,dap-ui--debug-window-buffer . ((side . bottom) (slot . 2) (window-height . 0.2)))))
+  :config
+  (dap-mode t)
+  (dap-ui-mode t)
+  (dap-tooltip-mode t)
+  (tooltip-mode t))
+
+;; I don't want to have the icons as an overlay in the UI, I prefer to
+;; use the bindings or the mapping provided by hydra
+(eval-after-load 'lsp-mode '(advice-add 'dap-ui--update-controls :override #'ignore))
+
 (use-package sh-script
   :mode ("bashrc" . sh-mode)
   :hook (after-save . executable-make-buffer-file-executable-if-script-p)
@@ -76,7 +103,8 @@
 (use-package go-mode
   :ensure t
   :hook ((before-save . lsp-format-buffer)
-         (before-save . lsp-organize-imports))
+         (before-save . lsp-organize-imports)
+         (go-mode . fcuny/setup-go-mode-compile))
   :config
   (when (memq window-system '(mac ns))
     (exec-path-from-shell-copy-env "GOPATH"))
@@ -96,4 +124,9 @@
   :bind (:map puppet-mode-map
               ("C-c |" . puppet-align-block)))
 
+(defun fcuny/setup-go-mode-compile ()
+  (if (not (string-match "go" compile-command))
+      (set (make-local-variable 'compile-command)
+           "go build -v")))
+
 (provide 'fcuny-prog)
diff --git a/emacs/custom/fcuny-ui.el b/emacs/custom/fcuny-ui.el
index 693c0a9..c350088 100644
--- a/emacs/custom/fcuny-ui.el
+++ b/emacs/custom/fcuny-ui.el
@@ -84,4 +84,8 @@
   (setq uniquify-buffer-name-style 'forward)
   (setq uniquify-separator "/"))
 
+;; required for dap-mode and dap-ui-mode
+(use-package posframe
+  :ensure t)
+
 (provide 'fcuny-ui)