dap-python hangs emacs's whole UI when debugged process exits (maybe?)

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Attempting to try out dap-mode, I used dap-debug with Python :: run file (buffer) on twisted/python/filepath.py (on b2a7af4ffcb47f52fe3c951953148fd9becf50a8, if anyone cares about the specifics). I selected debugpy, set a breakpoint on line 34, and started stepping through. It actually worked (after I realized that #528 was preventing anything from working).

After a little bit I thought "okay, I should probably dap-continue to see what happens when the debugger exits" and Emacs locked up for the better part of 10 minutes, despite numerous frantic mashings of C-g. Eventually, the Messages buffer said:

Debug session process exited with status: killed: 9

No message handler for debugpySockets

and Emacs became responsive again.

[glyph]

"(maybe?)" because this is my first experience with dap-mode and I don't know if there's anything interesting about my environment. I don't think there is.

[gamboz]

Similar problem here (emacs 30.1, dap-mode @master). Emacs hangs when the UI is triggered and I need to give 3 C-g to regain control.

I can't pinpoint the issue, but, trying to profile (M-x profiler-start, etc.) I think I get many calls to timer-event-handler that look suspicious

• debug-test with no breakpoint

         409  61% + command-execute
         152  22% + redisplay_internal (C function)
          65   9% + #<byte-code-function 780>
          36   5% + timer-event-handler
           2   0% + #<byte-code-function 21C>
           2   0%   clm/log-command
           0   0%   ...
  

• debug-test with breakpoint

        2446  61% + timer-event-handler
         588  14% + command-execute
         384   9% + redisplay_internal (C function)
         286   7%   Automatic GC
         250   6% + #<byte-code-function 76A>
           6   0% + #<byte-code-function F30>
           2   0%   help-command-error-confusable-suggestions
           2   0% + undo-auto--add-boundary
           0   0%   ...
  

HTH

[dfireBird]

Similar problem here as well, emacs 30.1 and dap mode at master branch. UI hangs for me when I trigger the rust-analyzer's debug command to debug a test, instead of using C-g, I instead ran pkill -SIGUSR2 emacs to trigger the debugger and give me a backtrace:

Debugger entered--Lisp error: (quit)
  -butlast(nil)
  treemacs-update-node((lsp-treemacs-generic-root))
  lsp-treemacs-generic-refresh()
  lsp-treemacs-generic-update(((:key "Locals" :label "Locals" :icon dap-scope :children #f(compiled-function (&rest args2) #<bytecode -0xeeaa1f677f16c84>)) (:key "Registers" :label "Registers" :icon dap-scope :children #f(compiled-function (&rest args2) #<bytecode -0xeeaa1f663f16c84>))))
  dap-ui-locals--refresh()
  apply(dap-ui-locals--refresh nil)
  timer-event-handler([t 0 0 200000 nil dap-ui-locals--refresh nil idle 0 nil])

With @gamboz 's comment and this, looks like some issue with lsp-treemacs refresh method.

[dsyzling]

I'm seeing a similar issue with debugging via Python/debugpy and dap-debug pytest at point with Emacs 30.1 under WSL. But I also see this debugging simple python scripts.

If I use toggle-debug-on-quit - start debugging with dap-debug and hit a breakpoint, hit C-g 3 times, the following stacktrace is produced.

Debugger entered--Lisp error: (quit)
  (not (gethash detour treemacs-dom nil))
  (while (not (gethash detour treemacs-dom nil)) (setq detour (let ((path detour)) (cond ((stringp path) (let* ((path ...)) (if (and ... ...) (substring path 0 -1) path))) ((or (symbolp detour) (symbolp (car detour)) (stringp (car detour))) (-butlast detour)) (t (user-error "Path %s appears to be neither a file nor an extension" detour))))))
  (let* ((detour (let ((path curr-file)) (cond ((stringp path) (let* (...) (if ... ... path))) ((or (symbolp curr-file) (symbolp ...) (stringp ...)) (-butlast curr-file)) (t (user-error "Path %s appears to be neither a file nor an extension" curr-file)))))) (while (not (gethash detour treemacs-dom nil)) (setq detour (let ((path detour)) (cond ((stringp path) (let* (...) (if ... ... path))) ((or (symbolp detour) (symbolp ...) (stringp ...)) (-butlast detour)) (t (user-error "Path %s appears to be neither a file nor an extension" detour)))))) (let ((result (treemacs--find-custom-node detour))) (if result (progn (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if (eq ... ...) (progn ...)))) (hl-line-highlight) (let ((window (get-buffer-window))) (if window (progn (set-window-point window ...)))) result))))
  (cond ((gethash curr-node-path treemacs-dom nil) (let ((result (treemacs--find-custom-node curr-node-path))) (if result (progn (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if ... ...))) (hl-line-highlight) (let ((window ...)) (if window (progn ...))) result)))) ((and next-path (gethash next-path treemacs-dom nil)) (let ((result (treemacs--find-custom-node next-path))) (if result (progn (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if ... ...))) (hl-line-highlight) (let ((window ...)) (if window (progn ...))) result)))) ((and prev-path (gethash prev-path treemacs-dom nil)) (let ((result (treemacs--find-custom-node prev-path))) (if result (progn (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if ... ...))) (hl-line-highlight) (let ((window ...)) (if window (progn ...))) result)))) (t (let* ((detour (let ((path curr-file)) (cond (... ...) (... ...) (t ...))))) (while (not (gethash detour treemacs-dom nil)) (setq detour (let ((path detour)) (cond (... ...) (... ...) (t ...))))) (let ((result (treemacs--find-custom-node detour))) (if result (progn (if (eq major-mode ...) (progn ... ...)) (hl-line-highlight) (let (...) (if window ...)) result))))))
  (let nil (cond ((gethash curr-node-path treemacs-dom nil) (let ((result (treemacs--find-custom-node curr-node-path))) (if result (progn (if (eq major-mode ...) (progn ... ...)) (hl-line-highlight) (let (...) (if window ...)) result)))) ((and next-path (gethash next-path treemacs-dom nil)) (let ((result (treemacs--find-custom-node next-path))) (if result (progn (if (eq major-mode ...) (progn ... ...)) (hl-line-highlight) (let (...) (if window ...)) result)))) ((and prev-path (gethash prev-path treemacs-dom nil)) (let ((result (treemacs--find-custom-node prev-path))) (if result (progn (if (eq major-mode ...) (progn ... ...)) (hl-line-highlight) (let (...) (if window ...)) result)))) (t (let* ((detour (let (...) (cond ... ... ...)))) (while (not (gethash detour treemacs-dom nil)) (setq detour (let (...) (cond ... ... ...)))) (let ((result (treemacs--find-custom-node detour))) (if result (progn (if ... ...) (hl-line-highlight) (let ... ...) result)))))))
  (cond ((memq curr-state '(root-node-closed root-node-open)) (let nil (let ((result (treemacs-find-file-node curr-file nil))) (if result (progn (if (eq major-mode ...) (progn ... ...)) (hl-line-highlight) (let (...) (if window ...)) result))))) ((memq curr-state '(file-node-closed file-node-open dir-node-closed dir-node-open)) (let nil (if (and (gethash curr-file treemacs-dom nil) (or treemacs-show-hidden-files (not (s-matches? treemacs-dotfiles-regex ...)))) (let ((result (treemacs-find-file-node curr-file nil))) (if result (progn (if ... ...) (hl-line-highlight) (let ... ...) result))) (let* ((--cl-can-move-to-- #'...)) (cond ((and next-path ...) (let ... ...)) ((and prev-path ...) (let ... ...)) (t (let* ... ... ...))))))) ((memq curr-state '(tag-node tag-node-closed tag-node-open)) (let nil (treemacs-goto-node curr-node-path))) ((null curr-state) (let nil (goto-char curr-point))) (t (let nil (cond ((gethash curr-node-path treemacs-dom nil) (let ((result ...)) (if result (progn ... ... ... result)))) ((and next-path (gethash next-path treemacs-dom nil)) (let ((result ...)) (if result (progn ... ... ... result)))) ((and prev-path (gethash prev-path treemacs-dom nil)) (let ((result ...)) (if result (progn ... ... ... result)))) (t (let* ((detour ...)) (while (not ...) (setq detour ...)) (let (...) (if result ...))))))))
  (let* ((curr-btn (let ((result (text-property-not-all (line-beginning-position) (line-end-position) 'button nil))) (if result (progn (copy-marker result t))))) (curr-point (point-marker)) (next-path (let ((result (let (...) (if result ...)))) (if result (progn (button-get result :path))))) (prev-path (let ((result (let (...) (if result ...)))) (if result (progn (button-get result :path))))) (curr-node-path (let ((result curr-btn)) (if result (progn (get-text-property result :path))))) (curr-state (let ((result curr-btn)) (if result (progn (get-text-property result :state))))) (collapse (let ((result curr-btn)) (if result (progn (get-text-property result :collapsed))))) (curr-file (if collapse (get-text-property curr-btn :key) (let ((result curr-btn)) (if result (progn (treemacs--nearest-path result)))))) (curr-window (get-buffer-window (current-buffer))) (curr-win-line (if curr-window (progn (let ((save-selected-window--state ...)) (save-current-buffer (unwind-protect ... ...))))))) (let ((treemacs--no-recenter t)) (let ((btn (if force-expand (treemacs-goto-node path) (let (...) (if result ...))))) (if btn (if (memq (get-text-property btn :state) treemacs--open-node-states) (let* ((close-func ...)) (funcall close-func) (if (eq 1 ...) (progn ...))) (if force-expand (progn (funcall ...)))) (let ((dom-node (gethash path treemacs-dom nil))) (if dom-node (progn (let* ... ...))))))) (cond ((memq curr-state '(root-node-closed root-node-open)) (let nil (let ((result (treemacs-find-file-node curr-file nil))) (if result (progn (if ... ...) (hl-line-highlight) (let ... ...) result))))) ((memq curr-state '(file-node-closed file-node-open dir-node-closed dir-node-open)) (let nil (if (and (gethash curr-file treemacs-dom nil) (or treemacs-show-hidden-files (not ...))) (let ((result ...)) (if result (progn ... ... ... result))) (let* ((--cl-can-move-to-- ...)) (cond (... ...) (... ...) (t ...)))))) ((memq curr-state '(tag-node tag-node-closed tag-node-open)) (let nil (treemacs-goto-node curr-node-path))) ((null curr-state) (let nil (goto-char curr-point))) (t (let nil (cond ((gethash curr-node-path treemacs-dom nil) (let (...) (if result ...))) ((and next-path (gethash next-path treemacs-dom nil)) (let (...) (if result ...))) ((and prev-path (gethash prev-path treemacs-dom nil)) (let (...) (if result ...))) (t (let* (...) (while ... ...) (let ... ...))))))) (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if (eq 'image (car-safe (get-text-property (point) 'display))) (progn (forward-char 1))))) (if (get-text-property (point) 'invisible) (progn (goto-char (or (next-single-property-change (point) 'invisible) (point-min))))) (if curr-win-line (progn (let* ((buffer-point (point))) (let ((save-selected-window--state (internal--before-with-selected-window curr-window))) (save-current-buffer (unwind-protect (progn ... ... ...) (internal--after-with-selected-window save-selected-window--state))))))))
  (let ((treemacs--ready-to-follow nil)) (ignore treemacs--ready-to-follow) nil (let* ((curr-btn (let ((result (text-property-not-all ... ... ... nil))) (if result (progn (copy-marker result t))))) (curr-point (point-marker)) (next-path (let ((result (let ... ...))) (if result (progn (button-get result :path))))) (prev-path (let ((result (let ... ...))) (if result (progn (button-get result :path))))) (curr-node-path (let ((result curr-btn)) (if result (progn (get-text-property result :path))))) (curr-state (let ((result curr-btn)) (if result (progn (get-text-property result :state))))) (collapse (let ((result curr-btn)) (if result (progn (get-text-property result :collapsed))))) (curr-file (if collapse (get-text-property curr-btn :key) (let ((result curr-btn)) (if result (progn ...))))) (curr-window (get-buffer-window (current-buffer))) (curr-win-line (if curr-window (progn (let (...) (save-current-buffer ...)))))) (let ((treemacs--no-recenter t)) (let ((btn (if force-expand (treemacs-goto-node path) (let ... ...)))) (if btn (if (memq (get-text-property btn :state) treemacs--open-node-states) (let* (...) (funcall close-func) (if ... ...)) (if force-expand (progn ...))) (let ((dom-node ...)) (if dom-node (progn ...)))))) (cond ((memq curr-state '(root-node-closed root-node-open)) (let nil (let ((result ...)) (if result (progn ... ... ... result))))) ((memq curr-state '(file-node-closed file-node-open dir-node-closed dir-node-open)) (let nil (if (and (gethash curr-file treemacs-dom nil) (or treemacs-show-hidden-files ...)) (let (...) (if result ...)) (let* (...) (cond ... ... ...))))) ((memq curr-state '(tag-node tag-node-closed tag-node-open)) (let nil (treemacs-goto-node curr-node-path))) ((null curr-state) (let nil (goto-char curr-point))) (t (let nil (cond ((gethash curr-node-path treemacs-dom nil) (let ... ...)) ((and next-path ...) (let ... ...)) ((and prev-path ...) (let ... ...)) (t (let* ... ... ...)))))) (if (eq major-mode 'treemacs-mode) (progn (beginning-of-line) (if (eq 'image (car-safe (get-text-property ... ...))) (progn (forward-char 1))))) (if (get-text-property (point) 'invisible) (progn (goto-char (or (next-single-property-change (point) 'invisible) (point-min))))) (if curr-win-line (progn (let* ((buffer-point (point))) (let ((save-selected-window--state ...)) (save-current-buffer (unwind-protect ... ...))))))))
  treemacs-update-node((lsp-treemacs-generic-root))
  lsp-treemacs-generic-refresh()
  lsp-treemacs-generic-update(((:key "Locals" :label "Locals" :icon dap-scope :children #f(compiled-function (&rest args2) #<bytecode -0x16791f799cd36dda>)) (:key "Globals" :label "Globals" :icon dap-scope :children #f(compiled-function (&rest args2) #<bytecode -0x16791f79a0d36dda>))))
  dap-ui-locals--refresh()
  apply(dap-ui-locals--refresh nil)
  timer-event-handler([t 0 0 200000 nil dap-ui-locals--refresh nil idle 0 nil])

[dsyzling]

@yyoncho if I replace treemacs-update-node with treemacs-do-update-node in the function lsp-treemacs-generic-refresh, this seems to prevent the lock up. I'm not sure if there's an issue with multiple calls to update node being made or something in treemacs-save-position that's causing an issue. I can see why it makes sense to call save-position in this way with a refresh, but there's some odd interaction going on.

So for example:

(defun lsp-treemacs-generic-refresh (&optional _cache)
  (condition-case _err
      (let ((inhibit-read-only t))
        (treemacs-do-update-node '(lsp-treemacs-generic-root)))
    (error)))

[aalystama]

Hi everyone! Had similar issue #844. Replacing treemacs-update-node with treemacs-do-update-one, as @dsyzling suggested, helped in my case too.

[dsyzling]

See updates to #844 for a possible issue with treemacs-save-position macro causing this issue.

[dsyzling]

The fix has now been applied to treemacs so if you update your Emacs packages to include treemacs-20250423.2024 the dap-mode lockup should be resolved. If a few others could verify this we can close this isuse. See the following treemacs issue for details: Alexander-Miller/treemacs#1151

[gamboz]

If a few others could verify this...

I confirm that lockup is resolved when using latest treemacs (820b09d) 🥰

Kudos @dsyzling et al.!