Add backtrace-mode and use it in the debugger, ERT and Edebug

* doc/lispref/debugging.texi (Using Debugger): Remove explanation of
backtrace buffer.  Refer to new node.
(Backtraces): New node.
(Debugger Commands): Refer to new node.  Remove 'v'.
* doc/lispref/edebug.texi (Edebug Misc): Refer to new node.
* doc/misc/ert.texi (Running Tests Interactively): Refer to new node.

* lisp/emacs-lisp-backtrace.el: New file.
* test/lisp/emacs-lisp/backtrace-tests.el: New file.

* lisp/emacs-lisp/debug.el: (debugger-buffer-state): New cl-defstruct.
(debugger--restore-buffer-state): New function.
(debug): Use a debugger-buffer-state object to save and restore buffer
state.  Fix bug#15749 by leaving an unused buffer in debugger-mode,
empty, instead of in fundamental-mode, and then when reusing a buffer,
not calling debugger-mode if the buffer is already in debugger-mode.
(debugger-insert-backtrace): Remove.
(debugger-setup-buffer): Use backtrace-mode.
(debugger--insert-header): New function.
(debugger-continue, debugger-return-value): Change check for flags to
use backtrace-frames.
(debugger-frame-number): Determine backtrace frame number from
backtrace-frames.
(debugger--locals-visible-p, debugger--insert-locals)
(debugger--show-locals, debugger--hide-locals)
(debugger-toggle-locals): Remove.
(debugger-mode-map): Make a child of backtrace-mode-map.  Move
navigation commands to backtrace-mode-map.  Bind 'q' to debugger-quit
instead of top-level.  Make Help Follow menu item call
backtrace-help-follow-symbol.
(debugger-mode): Derive from backtrace-mode.
(debug-help-follow): Remove.  Move body of this function to
'backtrace-help-follow-symbol' in backtrace.el.
(debugger-quit): New function.

* lisp/emacs-lisp/edebug.el (edebug-unwrap-results): Remove warning
in docstring about circular results.
(edebug-unwrap): Use pcase.
(edebug-unwrap1): New function to unwrap circular objects.
(edebug-unwrap*): Use it.
(edebug--frame): New cl-defstruct.
(edebug-backtrace): Call the buffer *Edebug Backtrace* and use
backtrace-mode.  Get the frames from edebug--backtrace-frames.
(edebug--backtrace-frames, edebug--unwrap-and-add-info)
(edebug--symbol-not-prefixed-p): New functions.

* lisp/emacs-lisp/lisp-mode.el
(lisp-el-font-lock-keywords-for-backtraces)
(lisp-el-font-lock-keywords-for-backtraces-1)
(lisp-el-font-lock-keywords-for-backtraces-2): New constants.

* lisp/emacs-lisp/ert.el (ert--print-backtrace): Remove.
(ert--run-test-debugger): Use backtrace-get-frames.
(ert-run-tests-batch): Use backtrace-to-string.
(ert-results-pop-to-backtrace-for-test-at-point): Use backtrace-mode.
(ert--insert-backtrace-header): New function.

* tests/lisp/emacs-lisp/ert-tests.el (ert-test--which-file):
Use backtrace-frame slot accessor.

1 files changed, 18 insertions, 24 deletions

diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index cad21044f15..7178493ebe5 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -60,6 +60,7 @@
 (require 'cl-lib)
 (require 'button)
 (require 'debug)
+(require 'backtrace)
 (require 'easymenu)
 (require 'ewoc)
 (require 'find-func)
@@ -677,13 +678,6 @@ and is displayed in front of the value of MESSAGE-FORM."
 (cl-defstruct (ert-test-aborted-with-non-local-exit
                (:include ert-test-result)))
 
-(defun ert--print-backtrace (backtrace do-xrefs)
-  "Format the backtrace BACKTRACE to the current buffer."
-  (let ((print-escape-newlines t)
-        (print-level 8)
-        (print-length 50))
-    (debugger-insert-backtrace backtrace do-xrefs)))
-
 ;; A container for the state of the execution of a single test and
 ;; environment data needed during its execution.
 (cl-defstruct ert--test-execution-info
@@ -732,7 +726,7 @@ run.  ARGS are the arguments to `debugger'."
               ;; use.
               ;;
               ;; Grab the frames above the debugger.
-              (backtrace (cdr (backtrace-frames debugger)))
+              (backtrace (cdr (backtrace-get-frames debugger)))
               (infos (reverse ert--infos)))
          (setf (ert--test-execution-info-result info)
                (cl-ecase type
@@ -1406,9 +1400,8 @@ Returns the stats object."
               (ert-test-result-with-condition
                (message "Test %S backtrace:" (ert-test-name test))
                (with-temp-buffer
-                 (ert--print-backtrace
-                  (ert-test-result-with-condition-backtrace result)
-                  nil)
+                 (insert (backtrace-to-string
+                          (ert-test-result-with-condition-backtrace result)))
                  (if (not ert-batch-backtrace-right-margin)
                      (message "%s"
                               (buffer-substring-no-properties (point-min)
@@ -2450,20 +2443,21 @@ To be used in the ERT results buffer."
     (cl-etypecase result
       (ert-test-passed (error "Test passed, no backtrace available"))
       (ert-test-result-with-condition
-       (let ((backtrace (ert-test-result-with-condition-backtrace result))
-             (buffer (get-buffer-create "*ERT Backtrace*")))
+       (let ((buffer (get-buffer-create "*ERT Backtrace*")))
          (pop-to-buffer buffer)
-         (let ((inhibit-read-only t))
-           (buffer-disable-undo)
-           (erase-buffer)
-           (ert-simple-view-mode)
-           (set-buffer-multibyte t)     ; mimic debugger-setup-buffer
-           (setq truncate-lines t)
-           (ert--print-backtrace backtrace t)
-           (goto-char (point-min))
-           (insert (substitute-command-keys "Backtrace for test `"))
-           (ert-insert-test-name-button (ert-test-name test))
-           (insert (substitute-command-keys "':\n"))))))))
+         (unless (derived-mode-p 'backtrace-mode)
+           (backtrace-mode))
+         (setq backtrace-insert-header-function
+               (lambda () (ert--insert-backtrace-header (ert-test-name test)))
+               backtrace-frames (ert-test-result-with-condition-backtrace result)
+               backtrace-view '(:do-xrefs t))
+         (backtrace-print)
+         (goto-char (point-min)))))))
+
+(defun ert--insert-backtrace-header (name)
+  (insert (substitute-command-keys "Backtrace for test `"))
+  (ert-insert-test-name-button name)
+  (insert (substitute-command-keys "':\n")))
 
 (defun ert-results-pop-to-messages-for-test-at-point ()
   "Display the part of the *Messages* buffer generated during the test at point.