bug#24514: 24.5; [WIP][PATCH] Lispy backtraces

[Vasilij Schneidermann <v.schneidermann@gmail.com>]

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Hello again,

I've updated the patch as suggested to make the behavior configurable.
I'm pretty sure though that the customization option's name is terrible.
Any suggestions for a better one?

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From 7b953b3ec64b26edd812d0ad3e4e01bad4f94193 Mon Sep 17 00:00:00 2001
From: Vasilij Schneidermann <v.schneidermann@gmail.com>
Date: Thu, 22 Sep 2016 23:01:21 +0200
Subject: [PATCH] Make backtraces great again

---
 lisp/emacs-lisp/debug.el  |  4 +++-
 lisp/emacs-lisp/edebug.el |  4 +++-
 src/eval.c                | 12 ++++++++++--
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index 22a3f39..c481ee2 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -279,7 +279,9 @@ That buffer should be current already."
   (goto-char (point-min))
   (delete-region (point)
 		 (progn
-		   (search-forward "\n  debug(")
+		   (search-forward (if debugger-lispy-backtrace
+                                       "\n  (debug "
+                                     "\n  debug("))
 		   (forward-line (if (eq (car args) 'debug)
                                      ;; Remove debug--implement-debug-on-entry
                                      ;; and the advice's `apply' frame.
diff --git a/lisp/emacs-lisp/edebug.el b/lisp/emacs-lisp/edebug.el
index c283c16..a2e9c00 100644
--- a/lisp/emacs-lisp/edebug.el
+++ b/lisp/emacs-lisp/edebug.el
@@ -3797,7 +3797,9 @@ Otherwise call `debug' normally."
 	  (forward-line 1)
 	  (delete-region last-ok-point (point)))
 
-	 ((looking-at "^  edebug")
+	 ((looking-at (if debugger-lispy-backtrace
+                          "^  (edebug"
+                        "^  edebug"))
 	  (forward-line 1)
 	  (delete-region last-ok-point (point))
 	  )))
diff --git a/src/eval.c b/src/eval.c
index 72facd5..fc6e5a6 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3409,13 +3409,17 @@ Output stream used is value of `standard-output'.  */)
       else
 	{
 	  tem = backtrace_function (pdl);
+	  if (debugger_lispy_backtrace)
+	    write_string ("(");
 	  Fprin1 (tem, Qnil);	/* This can QUIT.  */
-	  write_string ("(");
+	  if (!debugger_lispy_backtrace)
+	    write_string ("(");
 	  {
 	    ptrdiff_t i;
 	    for (i = 0; i < backtrace_nargs (pdl); i++)
 	      {
-		if (i) write_string (" ");
+		if (i || debugger_lispy_backtrace)
+		  write_string(" ");
 		Fprin1 (backtrace_args (pdl)[i], Qnil);
 	      }
 	  }
@@ -3838,6 +3842,10 @@ This is nil when the debugger is called under circumstances where it
 might not be safe to continue.  */);
   debugger_may_continue = 1;
 
+  DEFVAR_BOOL ("debugger-lispy-backtrace", debugger_lispy_backtrace,
+	       doc: /* Non-nil means display call stack frames as lists. */);
+  debugger_lispy_backtrace = 0;
+
   DEFVAR_LISP ("debugger", Vdebugger,
 	       doc: /* Function to call to invoke debugger.
 If due to frame exit, args are `exit' and the value being returned;
-- 
2.9.3