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diff --git a/lisp/emacs-lisp/backtrace.el b/lisp/emacs-lisp/backtrace.el new file mode 100644 index 00000000000..e82d4f5a5a2 --- /dev/null +++ b/lisp/emacs-lisp/backtrace.el @@ -0,0 +1,918 @@ +;;; backtrace.el --- generic major mode for Elisp backtraces -*- lexical-binding: t -*- + +;; Copyright (C) 2018 Free Software Foundation, Inc. + +;; Author: Gemini Lasswell +;; Keywords: lisp, tools, maint +;; Version: 1.0 + +;; This file is part of GNU Emacs. + +;; GNU Emacs is free software: you can redistribute it and/or modify +;; it under the terms of the GNU General Public License as published by +;; the Free Software Foundation, either version 3 of the License, or +;; (at your option) any later version. + +;; GNU Emacs is distributed in the hope that it will be useful, +;; but WITHOUT ANY WARRANTY; without even the implied warranty of +;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +;; GNU General Public License for more details. + +;; You should have received a copy of the GNU General Public License +;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>. + +;;; Commentary: + +;; This file defines Backtrace mode, a generic major mode for displaying +;; Elisp stack backtraces, which can be used as is or inherited from +;; by another mode. + +;; For usage information, see the documentation of `backtrace-mode'. + +;;; Code: + +(eval-when-compile (require 'cl-lib)) +(eval-when-compile (require 'pcase)) +(eval-when-compile (require 'subr-x)) ; if-let +(require 'find-func) +(require 'help-mode) ; Define `help-function-def' button type. +(require 'lisp-mode) + +;;; Options + +(defgroup backtrace nil + "Viewing of Elisp backtraces." + :group 'lisp) + +(defcustom backtrace-fontify t + "If non-nil, fontify Backtrace buffers. +Set to nil to disable fontification, which may be necessary in +order to debug the code that does fontification." + :type 'boolean + :group 'backtrace + :version "27.1") + +(defcustom backtrace-line-length 5000 + "Target length for lines in Backtrace buffers. +Backtrace mode will attempt to abbreviate printing of backtrace +frames to make them shorter than this, but success is not +guaranteed. If set to nil or zero, Backtrace mode will not +abbreviate the forms it prints." + :type 'integer + :group 'backtrace + :version "27.1") + +;;; Backtrace frame data structure + +(cl-defstruct + (backtrace-frame + (:constructor backtrace-make-frame)) + evald ; Non-nil if argument evaluation is complete. + fun ; The function called/to call in this frame. + args ; Either evaluated or unevaluated arguments to the function. + flags ; A plist, possible properties are :debug-on-exit and :source-available. + locals ; An alist containing variable names and values. + buffer ; If non-nil, the buffer in use by eval-buffer or eval-region. + pos ; The position in the buffer. + ) + +(cl-defun backtrace-get-frames + (&optional base &key (constructor #'backtrace-make-frame)) + "Collect all frames of current backtrace into a list. +The list will contain objects made by CONSTRUCTOR, which +defaults to `backtrace-make-frame' and which, if provided, should +be the constructor of a structure which includes +`backtrace-frame'. If non-nil, BASE should be a function, and +frames before its nearest activation frame are discarded." + (let ((frames nil) + (eval-buffers eval-buffer-list)) + (mapbacktrace (lambda (evald fun args flags) + (push (funcall constructor + :evald evald :fun fun + :args args :flags flags) + frames)) + (or base 'backtrace-get-frames)) + (setq frames (nreverse frames)) + ;; Add local variables to each frame, and the buffer position + ;; to frames containing eval-buffer or eval-region. + (dotimes (idx (length frames)) + (let ((frame (nth idx frames))) + ;; `backtrace--locals' gives an error when idx is 0. But the + ;; locals for frame 0 are not needed, because when we get here + ;; from debug-on-entry, the locals aren't bound yet, and when + ;; coming from Edebug or ERT there is an Edebug or ERT + ;; function at frame 0. + (when (> idx 0) + (setf (backtrace-frame-locals frame) + (backtrace--locals idx (or base 'backtrace-get-frames)))) + (when (and eval-buffers (memq (backtrace-frame-fun frame) + '(eval-buffer eval-region))) + ;; This will get the wrong result if there are two nested + ;; eval-region calls for the same buffer. That's not a very + ;; useful case. + (with-current-buffer (pop eval-buffers) + (setf (backtrace-frame-buffer frame) (current-buffer)) + (setf (backtrace-frame-pos frame) (point)))))) + frames)) + +;; Button definition for jumping to a buffer position. + +(define-button-type 'backtrace-buffer-pos + 'action #'backtrace--pop-to-buffer-pos + 'help-echo "mouse-2, RET: Show reading position") + +(defun backtrace--pop-to-buffer-pos (button) + "Pop to the buffer and position for the BUTTON at point." + (let* ((buffer (button-get button 'backtrace-buffer)) + (pos (button-get button 'backtrace-pos))) + (if (buffer-live-p buffer) + (progn + (pop-to-buffer buffer) + (goto-char (max (point-min) (min (point-max) pos)))) + (message "Buffer has been killed")))) + +;; Font Locking support + +(defconst backtrace--font-lock-keywords + '((backtrace--match-ellipsis-in-string + (1 'button prepend))) + "Expressions to fontify in Backtrace mode. +Fontify these in addition to the expressions Emacs Lisp mode +fontifies.") + +(defconst backtrace-font-lock-keywords + (append lisp-el-font-lock-keywords-for-backtraces + backtrace--font-lock-keywords) + "Default expressions to highlight in Backtrace mode.") +(defconst backtrace-font-lock-keywords-1 + (append lisp-el-font-lock-keywords-for-backtraces-1 + backtrace--font-lock-keywords) + "Subdued level highlighting for Backtrace mode.") +(defconst backtrace-font-lock-keywords-2 + (append lisp-el-font-lock-keywords-for-backtraces-2 + backtrace--font-lock-keywords) + "Gaudy level highlighting for Backtrace mode.") + +(defun backtrace--match-ellipsis-in-string (bound) + ;; Fontify ellipses within strings as buttons. + ;; This is necessary because ellipses are text property buttons + ;; instead of overlay buttons, which is done because there could + ;; be a large number of them. + (when (re-search-forward "\\(\\.\\.\\.\\)\"" bound t) + (and (get-text-property (- (point) 2) 'cl-print-ellipsis) + (get-text-property (- (point) 3) 'cl-print-ellipsis) + (get-text-property (- (point) 4) 'cl-print-ellipsis)))) + +;;; Xref support + +(defun backtrace--xref-backend () 'elisp) + +;;; Backtrace mode variables + +(defvar-local backtrace-frames nil + "Stack frames displayed in the current Backtrace buffer. +This should be a list of `backtrace-frame' objects.") + +(defvar-local backtrace-view nil + "A plist describing how to render backtrace frames. +Possible entries are :show-flags, :show-locals and :print-circle.") + +(defvar-local backtrace-insert-header-function nil + "Function for inserting a header for the current Backtrace buffer. +If nil, no header will be created. Note that Backtrace buffers +are fontified as in Emacs Lisp Mode, the header text included.") + +(defvar backtrace-revert-hook nil + "Hook run before reverting a Backtrace buffer. +This is commonly used to recompute `backtrace-frames'.") + +(defvar-local backtrace-print-function #'cl-prin1 + "Function used to print values in the current Backtrace buffer.") + +(defvar-local backtrace-goto-source-functions nil + "Abnormal hook used to jump to the source code for the current frame. +Each hook function is called with no argument, and should return +non-nil if it is able to switch to the buffer containing the +source code. Execution of the hook will stop if one of the +functions returns non-nil. When adding a function to this hook, +you should also set the :source-available flag for the backtrace +frames where the source code location is known.") + +(defvar backtrace-mode-map + (let ((map (copy-keymap special-mode-map))) + (set-keymap-parent map button-buffer-map) + (define-key map "n" 'backtrace-forward-frame) + (define-key map "p" 'backtrace-backward-frame) + (define-key map "v" 'backtrace-toggle-locals) + (define-key map "#" 'backtrace-toggle-print-circle) + (define-key map "s" 'backtrace-goto-source) + (define-key map "\C-m" 'backtrace-help-follow-symbol) + (define-key map "+" 'backtrace-multi-line) + (define-key map "-" 'backtrace-single-line) + (define-key map "." 'backtrace-expand-ellipses) + (define-key map [follow-link] 'mouse-face) + (define-key map [mouse-2] 'mouse-select-window) + (easy-menu-define nil map "" + '("Backtrace" + ["Next Frame" backtrace-forward-frame + :help "Move cursor forwards to the start of a backtrace frame"] + ["Previous Frame" backtrace-backward-frame + :help "Move cursor backwards to the start of a backtrace frame"] + "--" + ["Show Variables" backtrace-toggle-locals + :style toggle + :active (backtrace-get-index) + :selected (plist-get (backtrace-get-view) :show-locals) + :help "Show or hide the local variables for the frame at point"] + ["Expand \"...\"s" backtrace-expand-ellipses + :help "Expand all the abbreviated forms in the current frame"] + ["Show on Multiple Lines" backtrace-multi-line + :help "Use line breaks and indentation to make a form more readable"] + ["Show on Single Line" backtrace-single-line] + "--" + ["Go to Source" backtrace-goto-source + :active (and (backtrace-get-index) + (plist-get (backtrace-frame-flags + (nth (backtrace-get-index) backtrace-frames)) + :source-available)) + :help "Show the source code for the current frame"] + ["Help for Symbol" backtrace-help-follow-symbol + :help "Show help for symbol at point"] + ["Describe Backtrace Mode" describe-mode + :help "Display documentation for backtrace-mode"])) + map) + "Local keymap for `backtrace-mode' buffers.") + +(defconst backtrace--flags-width 2 + "Width in characters of the flags for a backtrace frame.") + +;;; Navigation and Text Properties + +;; This mode uses the following text properties: +;; backtrace-index: The index into the buffer-local variable +;; `backtrace-frames' for the frame at point, or nil if outside of a +;; frame (in the buffer header). +;; backtrace-view: A plist describing how the frame is printed. See +;; the docstring for the buffer-local variable `backtrace-view. +;; backtrace-section: The part of a frame which point is in. Either +;; `func' or `locals'. At the moment just used to show and hide the +;; local variables. Derived modes which do additional printing +;; could define their own frame sections. +;; backtrace-form: A value applied to each printed representation of a +;; top-level s-expression, which needs to be different for sexps +;; printed adjacent to each other, so the limits can be quickly +;; found for pretty-printing. + +(defsubst backtrace-get-index (&optional pos) + "Return the index of the backtrace frame at POS. +The value is an index into `backtrace-frames', or nil. +POS, if omitted or nil, defaults to point." + (get-text-property (or pos (point)) 'backtrace-index)) + +(defsubst backtrace-get-section (&optional pos) + "Return the section of a backtrace frame at POS. +POS, if omitted or nil, defaults to point." + (get-text-property (or pos (point)) 'backtrace-section)) + +(defsubst backtrace-get-view (&optional pos) + "Return the view plist of the backtrace frame at POS. +POS, if omitted or nil, defaults to point." + (get-text-property (or pos (point)) 'backtrace-view)) + +(defsubst backtrace-get-form (&optional pos) + "Return the backtrace form data for the form printed at POS. +POS, if omitted or nil, defaults to point." + (get-text-property (or pos (point)) 'backtrace-form)) + +(defun backtrace-get-frame-start (&optional pos) + "Return the beginning position of the frame at POS in the buffer. +POS, if omitted or nil, defaults to point." + (let ((posn (or pos (point)))) + (if (or (= (point-min) posn) + (not (eq (backtrace-get-index posn) + (backtrace-get-index (1- posn))))) + posn + (previous-single-property-change posn 'backtrace-index nil (point-min))))) + +(defun backtrace-get-frame-end (&optional pos) + "Return the position of the end of the frame at POS in the buffer. +POS, if omitted or nil, defaults to point." + (next-single-property-change (or pos (point)) + 'backtrace-index nil (point-max))) + +(defun backtrace-forward-frame () + "Move forward to the beginning of the next frame." + (interactive) + (let ((max (backtrace-get-frame-end))) + (when (= max (point-max)) + (user-error "No next stack frame")) + (goto-char max))) + +(defun backtrace-backward-frame () + "Move backward to the start of a stack frame." + (interactive) + (let ((current-index (backtrace-get-index)) + (min (backtrace-get-frame-start))) + (if (or (and (/= (point) (point-max)) (null current-index)) + (= min (point-min)) + (and (= min (point)) + (null (backtrace-get-index (1- min))))) + (user-error "No previous stack frame")) + (if (= min (point)) + (goto-char (backtrace-get-frame-start (1- min))) + (goto-char min)))) + +;; Other Backtrace mode commands + +(defun backtrace-revert (&rest _ignored) + "The `revert-buffer-function' for `backtrace-mode'. +It runs `backtrace-revert-hook', then calls `backtrace-print'." + (interactive) + (unless (derived-mode-p 'backtrace-mode) + (error "The current buffer is not in Backtrace mode")) + (run-hooks 'backtrace-revert-hook) + (backtrace-print t)) + +(defmacro backtrace--with-output-variables (view &rest body) + "Bind output variables according to VIEW and execute BODY." + (declare (indent 1)) + `(let ((print-escape-control-characters t) + (print-escape-newlines t) + (print-circle (plist-get ,view :print-circle)) + (standard-output (current-buffer))) + ,@body)) + +(defun backtrace-toggle-locals (&optional all) + "Toggle the display of local variables for the backtrace frame at point. +With prefix argument ALL, toggle the value of :show-locals in +`backtrace-view', which affects all of the backtrace frames in +the buffer." + (interactive "P") + (if all + (let ((pos (make-marker)) + (visible (not (plist-get backtrace-view :show-locals)))) + (setq backtrace-view (plist-put backtrace-view :show-locals visible)) + (set-marker-insertion-type pos t) + (set-marker pos (point)) + (goto-char (point-min)) + ;; Skip the header. + (unless (backtrace-get-index) + (goto-char (backtrace-get-frame-end))) + (while (< (point) (point-max)) + (backtrace--set-frame-locals-visible visible) + (goto-char (backtrace-get-frame-end))) + (goto-char pos) + (when (invisible-p pos) + (goto-char (backtrace-get-frame-start)))) + (let ((index (backtrace-get-index))) + (unless index + (user-error "Not in a stack frame")) + (backtrace--set-frame-locals-visible + (not (plist-get (backtrace-get-view) :show-locals)))))) + +(defun backtrace--set-frame-locals-visible (visible) + "Set the visibility of the local vars for the frame at point to VISIBLE." + (let ((pos (point)) + (index (backtrace-get-index)) + (start (backtrace-get-frame-start)) + (end (backtrace-get-frame-end)) + (view (copy-sequence (backtrace-get-view))) + (inhibit-read-only t)) + (setq view (plist-put view :show-locals visible)) + (goto-char (backtrace-get-frame-start)) + (while (not (or (= (point) end) + (eq (backtrace-get-section) 'locals))) + (goto-char (next-single-property-change (point) + 'backtrace-section nil end))) + (cond + ((and (= (point) end) visible) + ;; The locals section doesn't exist so create it. + (let ((standard-output (current-buffer))) + (backtrace--with-output-variables view + (backtrace--print-locals + (nth index backtrace-frames) view)) + (add-text-properties end (point) `(backtrace-index ,index)) + (goto-char pos))) + ((/= (point) end) + ;; The locals section does exist, so add or remove the overlay. + (backtrace--set-locals-visible-overlay (point) end visible) + (goto-char (if (invisible-p pos) start pos)))) + (add-text-properties start (backtrace-get-frame-end) + `(backtrace-view ,view)))) + +(defun backtrace--set-locals-visible-overlay (beg end visible) + (backtrace--change-button-skip beg end (not visible)) + (if visible + (remove-overlays beg end 'invisible t) + (let ((o (make-overlay beg end))) + (overlay-put o 'invisible t) + (overlay-put o 'evaporate t)))) + +(defun backtrace--change-button-skip (beg end value) + "Change the skip property on all buttons between BEG and END. +Set it to VALUE unless the button is a `backtrace-ellipsis' button." + (let ((inhibit-read-only t)) + (setq beg (next-button beg)) + (while (and beg (< beg end)) + (unless (eq (button-type beg) 'backtrace-ellipsis) + (button-put beg 'skip value)) + (setq beg (next-button beg))))) + +(defun backtrace-toggle-print-circle (&optional all) + "Toggle `print-circle' for the backtrace frame at point. +With prefix argument ALL, toggle the value of :print-circle in +`backtrace-view', which affects all of the backtrace frames in +the buffer." + (interactive "P") + (backtrace--toggle-feature :print-circle all)) + +(defun backtrace--toggle-feature (feature all) + "Toggle FEATURE for the current backtrace frame or for the buffer. +FEATURE should be one of the options in `backtrace-view'. If ALL +is non-nil, toggle FEATURE for all frames in the buffer. After +toggling the feature, reprint the affected frame(s). Afterwards +position point at the start of the frame it was in before." + (if all + (let ((index (backtrace-get-index)) + (pos (point)) + (at-end (= (point) (point-max))) + (value (not (plist-get backtrace-view feature)))) + (setq backtrace-view (plist-put backtrace-view feature value)) + (goto-char (point-min)) + ;; Skip the header. + (unless (backtrace-get-index) + (goto-char (backtrace-get-frame-end))) + (while (< (point) (point-max)) + (backtrace--set-feature feature value) + (goto-char (backtrace-get-frame-end))) + (if (not index) + (goto-char (if at-end (point-max) pos)) + (goto-char (point-min)) + (while (and (not (eql index (backtrace-get-index))) + (< (point) (point-max))) + (goto-char (backtrace-get-frame-end))))) + (let ((index (backtrace-get-index))) + (unless index + (user-error "Not in a stack frame")) + (backtrace--set-feature feature + (not (plist-get (backtrace-get-view) feature)))))) + +(defun backtrace--set-feature (feature value) + "Set FEATURE in the view plist of the frame at point to VALUE. +Reprint the frame with the new view plist." + (let ((inhibit-read-only t) + (view (copy-sequence (backtrace-get-view))) + (index (backtrace-get-index)) + (min (backtrace-get-frame-start)) + (max (backtrace-get-frame-end))) + (setq view (plist-put view feature value)) + (delete-region min max) + (goto-char min) + (backtrace-print-frame (nth index backtrace-frames) view) + (add-text-properties min (point) + `(backtrace-index ,index backtrace-view ,view)) + (goto-char min))) + +(defun backtrace-expand-ellipsis (button) + "Expand display of the elided form at BUTTON." + (interactive) + (goto-char (button-start button)) + (unless (get-text-property (point) 'cl-print-ellipsis) + (if (and (> (point) (point-min)) + (get-text-property (1- (point)) 'cl-print-ellipsis)) + (backward-char) + (user-error "No ellipsis to expand here"))) + (let* ((end (next-single-property-change (point) 'cl-print-ellipsis)) + (begin (previous-single-property-change end 'cl-print-ellipsis)) + (value (get-text-property begin 'cl-print-ellipsis)) + (props (backtrace-get-text-properties begin)) + (inhibit-read-only t)) + (backtrace--with-output-variables (backtrace-get-view) + (delete-region begin end) + (insert (cl-print-to-string-with-limit #'cl-print-expand-ellipsis value + backtrace-line-length)) + (setq end (point)) + (goto-char begin) + (while (< (point) end) + (let ((next (next-single-property-change (point) 'cl-print-ellipsis + nil end))) + (when (get-text-property (point) 'cl-print-ellipsis) + (make-text-button (point) next :type 'backtrace-ellipsis)) + (goto-char next))) + (goto-char begin) + (add-text-properties begin end props)))) + +(defun backtrace-expand-ellipses (&optional no-limit) + "Expand display of all \"...\"s in the backtrace frame at point. +\\<backtrace-mode-map> +Each ellipsis will be limited to `backtrace-line-length' +characters in its expansion. With optional prefix argument +NO-LIMIT, do not limit the number of characters. Note that with +or without the argument, using this command can result in very +long lines and very poor display performance. If this happens +and is a problem, use `\\[revert-buffer]' to return to the +initial state of the Backtrace buffer." + (interactive "P") + (save-excursion + (let ((start (backtrace-get-frame-start)) + (end (backtrace-get-frame-end)) + (backtrace-line-length (unless no-limit backtrace-line-length))) + (goto-char end) + (while (> (point) start) + (let ((next (previous-single-property-change (point) 'cl-print-ellipsis + nil start))) + (when (get-text-property (point) 'cl-print-ellipsis) + (push-button (point))) + (goto-char next)))))) + +(defun backtrace-multi-line () + "Show the top level s-expression at point on multiple lines with indentation." + (interactive) + (backtrace--reformat-sexp #'backtrace--multi-line)) + +(defun backtrace--multi-line () + "Pretty print the current buffer, then remove the trailing newline." + (set-syntax-table emacs-lisp-mode-syntax-table) + (pp-buffer) + (goto-char (1- (point-max))) + (delete-char 1)) + +(defun backtrace-single-line () + "Show the top level s-expression at point on one line." + (interactive) + (backtrace--reformat-sexp #'backtrace--single-line)) + +(defun backtrace--single-line () + "Replace line breaks and following indentation with spaces. +Works on the current buffer." + (goto-char (point-min)) + (while (re-search-forward "\n[[:blank:]]*" nil t) + (replace-match " "))) + +(defun backtrace--reformat-sexp (format-function) + "Reformat the top level sexp at point. +Locate the top level sexp at or following point on the same line, +and reformat it with FORMAT-FUNCTION, preserving the location of +point within the sexp. If no sexp is found before the end of +the line or buffer, signal an error. + +FORMAT-FUNCTION will be called without arguments, with the +current buffer set to a temporary buffer containing only the +content of the sexp." + (let* ((orig-pos (point)) + (pos (point)) + (tag (backtrace-get-form pos)) + (end (next-single-property-change pos 'backtrace-form)) + (begin (previous-single-property-change end 'backtrace-form + nil (point-min)))) + (unless tag + (when (or (= end (point-max)) (> end (point-at-eol))) + (user-error "No form here to reformat")) + (goto-char end) + (setq pos end + end (next-single-property-change pos 'backtrace-form) + begin (previous-single-property-change end 'backtrace-form + nil (point-min)))) + (let* ((offset (when (>= orig-pos begin) (- orig-pos begin))) + (offset-marker (when offset (make-marker))) + (content (buffer-substring begin end)) + (props (backtrace-get-text-properties begin)) + (inhibit-read-only t)) + (delete-region begin end) + (insert (with-temp-buffer + (insert content) + (when offset + (set-marker-insertion-type offset-marker t) + (set-marker offset-marker (+ (point-min) offset))) + (funcall format-function) + (when offset + (setq offset (- (marker-position offset-marker) (point-min)))) + (buffer-string))) + (when offset + (set-marker offset-marker (+ begin offset))) + (save-excursion + (goto-char begin) + (indent-sexp)) + (add-text-properties begin (point) props) + (if offset + (goto-char (marker-position offset-marker)) + (goto-char orig-pos))))) + +(defun backtrace-get-text-properties (pos) + "Return a plist of backtrace-mode's text properties at POS." + (apply #'append + (mapcar (lambda (prop) + (list prop (get-text-property pos prop))) + '(backtrace-section backtrace-index backtrace-view + backtrace-form)))) + +(defun backtrace-goto-source () + "If its location is known, jump to the source code for the frame at point." + (interactive) + (let* ((index (or (backtrace-get-index) (user-error "Not in a stack frame"))) + (frame (nth index backtrace-frames)) + (source-available (plist-get (backtrace-frame-flags frame) + :source-available))) + (unless (and source-available + (catch 'done + (dolist (func backtrace-goto-source-functions) + (when (funcall func) + (throw 'done t))))) + (user-error "Source code location not known")))) + +(defun backtrace-help-follow-symbol (&optional pos) + "Follow cross-reference at POS, defaulting to point. +For the cross-reference format, see `help-make-xrefs'." + (interactive "d") + (unless pos + (setq pos (point))) + (unless (push-button pos) + ;; Check if the symbol under point is a function or variable. + (let ((sym + (intern + (save-excursion + (goto-char pos) (skip-syntax-backward "w_") + (buffer-substring (point) + (progn (skip-syntax-forward "w_") + (point))))))) + (when (or (boundp sym) (fboundp sym) (facep sym)) + (describe-symbol sym))))) + +;; Print backtrace frames + +(defun backtrace-print (&optional remember-pos) + "Populate the current Backtrace mode buffer. +This erases the buffer and inserts printed representations of the +frames. Optional argument REMEMBER-POS, if non-nil, means to +move point to the entry with the same ID element as the current +line and recenter window line accordingly." + (let ((inhibit-read-only t) + entry-index saved-pt window-line) + (and remember-pos + (setq entry-index (backtrace-get-index)) + (when (eq (window-buffer) (current-buffer)) + (setq window-line + (count-screen-lines (window-start) (point))))) + (erase-buffer) + (when backtrace-insert-header-function + (funcall backtrace-insert-header-function)) + (dotimes (idx (length backtrace-frames)) + (let ((beg (point)) + (elt (nth idx backtrace-frames))) + (and entry-index + (equal entry-index idx) + (setq entry-index nil + saved-pt (point))) + (backtrace-print-frame elt backtrace-view) + (add-text-properties + beg (point) + `(backtrace-index ,idx backtrace-view ,backtrace-view)))) + (set-buffer-modified-p nil) + ;; If REMEMBER-POS was specified, move to the "old" location. + (if saved-pt + (progn (goto-char saved-pt) + (when window-line + (recenter window-line))) + (goto-char (point-min))))) + +;; Define button type used for ...'s. +;; Set skip property so you don't have to TAB through 100 of them to +;; get to the next function name. +(define-button-type 'backtrace-ellipsis + 'skip t 'action #'backtrace-expand-ellipsis + 'help-echo "mouse-2, RET: expand this ellipsis") + +(defun backtrace-print-to-string (obj &optional limit) + "Return a printed representation of OBJ formatted for backtraces. +Attempt to get the length of the returned string under LIMIT +charcters with appropriate settings of `print-level' and +`print-length.' LIMIT defaults to `backtrace-line-length'." + (backtrace--with-output-variables backtrace-view + (backtrace--print-to-string obj limit))) + +(defun backtrace--print-to-string (sexp &optional limit) + ;; This is for use by callers who wrap the call with + ;; backtrace--with-output-variables. + (setq limit (or limit backtrace-line-length)) + (with-temp-buffer + (insert (cl-print-to-string-with-limit #'backtrace--print sexp limit)) + ;; Add a unique backtrace-form property. + (put-text-property (point-min) (point) 'backtrace-form (gensym)) + ;; Make buttons from all the "..."s. Since there might be many of + ;; them, use text property buttons. + (goto-char (point-min)) + (while (< (point) (point-max)) + (let ((end (next-single-property-change (point) 'cl-print-ellipsis + nil (point-max)))) + (when (get-text-property (point) 'cl-print-ellipsis) + (make-text-button (point) end :type 'backtrace-ellipsis)) + (goto-char end))) + (buffer-string))) + +(defun backtrace-print-frame (frame view) + "Insert a backtrace FRAME at point formatted according to VIEW. +Tag the sections of the frame with the `backtrace-section' text +property for use by navigation." + (backtrace--with-output-variables view + (backtrace--print-flags frame view) + (backtrace--print-func-and-args frame view) + (backtrace--print-locals frame view))) + +(defun backtrace--print-flags (frame view) + "Print the flags of a backtrace FRAME if enabled in VIEW." + (let ((beg (point)) + (flag (plist-get (backtrace-frame-flags frame) :debug-on-exit)) + (source (plist-get (backtrace-frame-flags frame) :source-available))) + (when (plist-get view :show-flags) + (when source (insert ">")) + (when flag (insert "*"))) + (insert (make-string (- backtrace--flags-width (- (point) beg)) ?\s)) + (put-text-property beg (point) 'backtrace-section 'func))) + +(defun backtrace--print-func-and-args (frame _view) + "Print the function, arguments and buffer position of a backtrace FRAME. +Format it according to VIEW." + (let* ((beg (point)) + (evald (backtrace-frame-evald frame)) + (fun (backtrace-frame-fun frame)) + (args (backtrace-frame-args frame)) + (def (find-function-advised-original fun)) + (fun-file (or (symbol-file fun 'defun) + (and (subrp def) + (not (eq 'unevalled (cdr (subr-arity def)))) + (find-lisp-object-file-name fun def)))) + (fun-pt (point))) + (cond + ((and evald (not debugger-stack-frame-as-list)) + (if (atom fun) + (funcall backtrace-print-function fun) + (insert + (backtrace--print-to-string fun (when args (/ backtrace-line-length 2))))) + (if args + (insert (backtrace--print-to-string + args (max (truncate (/ backtrace-line-length 5)) + (- backtrace-line-length (- (point) beg))))) + ;; The backtrace-form property is so that backtrace-multi-line + ;; will find it. backtrace-multi-line doesn't do anything + ;; useful with it, just being consistent. + (let ((start (point))) + (insert "()") + (put-text-property start (point) 'backtrace-form t)))) + (t + (let ((fun-and-args (cons fun args))) + (insert (backtrace--print-to-string fun-and-args))) + (cl-incf fun-pt))) + (when fun-file + (make-text-button fun-pt (+ fun-pt + (length (backtrace--print-to-string fun))) + :type 'help-function-def + 'help-args (list fun fun-file))) + ;; After any frame that uses eval-buffer, insert a comment that + ;; states the buffer position it's reading at. + (when (backtrace-frame-pos frame) + (insert " ; Reading at ") + (let ((pos (point))) + (insert (format "buffer position %d" (backtrace-frame-pos frame))) + (make-button pos (point) :type 'backtrace-buffer-pos + 'backtrace-buffer (backtrace-frame-buffer frame) + 'backtrace-pos (backtrace-frame-pos frame)))) + (insert "\n") + (put-text-property beg (point) 'backtrace-section 'func))) + +(defun backtrace--print-locals (frame view) + "Print a backtrace FRAME's local variables according to VIEW. +Print them only if :show-locals is non-nil in the VIEW plist." + (when (plist-get view :show-locals) + (let* ((beg (point)) + (locals (backtrace-frame-locals frame))) + (if (null locals) + (insert " [no locals]\n") + (pcase-dolist (`(,symbol . ,value) locals) + (insert " ") + (backtrace--print symbol) + (insert " = ") + (insert (backtrace--print-to-string value)) + (insert "\n"))) + (put-text-property beg (point) 'backtrace-section 'locals)))) + +(defun backtrace--print (obj &optional stream) + "Attempt to print OBJ to STREAM using `backtrace-print-function'. +Fall back to `prin1' if there is an error." + (condition-case err + (funcall backtrace-print-function obj stream) + (error + (message "Error in backtrace printer: %S" err) + (prin1 obj stream)))) + +(defun backtrace-update-flags () + "Update the display of the flags in the backtrace frame at point." + (let ((view (backtrace-get-view)) + (begin (backtrace-get-frame-start))) + (when (plist-get view :show-flags) + (save-excursion + (goto-char begin) + (let ((props (backtrace-get-text-properties begin)) + (inhibit-read-only t) + (standard-output (current-buffer))) + (delete-char backtrace--flags-width) + (backtrace--print-flags (nth (backtrace-get-index) backtrace-frames) + view) + (add-text-properties begin (point) props)))))) + +(defun backtrace--filter-visible (beg end &optional _delete) + "Return the visible text between BEG and END." + (let ((result "")) + (while (< beg end) + (let ((next (next-single-char-property-change beg 'invisible))) + (unless (get-char-property beg 'invisible) + (setq result (concat result (buffer-substring beg (min end next))))) + (setq beg next))) + result)) + +;;; The mode definition + +(define-derived-mode backtrace-mode special-mode "Backtrace" + "Generic major mode for examining an Elisp stack backtrace. +This mode can be used directly, or other major modes can be +derived from it, using `define-derived-mode'. + +In this major mode, the buffer contains some optional lines of +header text followed by backtrace frames, each consisting of one +or more whole lines. + +Letters in this mode do not insert themselves; instead they are +commands. +\\<backtrace-mode-map> +\\{backtrace-mode-map} + +A mode which inherits from Backtrace mode, or a command which +creates a backtrace-mode buffer, should usually do the following: + + - Set `backtrace-revert-hook', if the buffer contents need + to be specially recomputed prior to `revert-buffer'. + - Maybe set `backtrace-insert-header-function' to a function to create + header text for the buffer. + - Set `backtrace-frames' (see below). + - Maybe modify `backtrace-view' (see below). + - Maybe set `backtrace-print-function'. + +A command which creates or switches to a Backtrace mode buffer, +such as `ert-results-pop-to-backtrace-for-test-at-point', should +initialize `backtrace-frames' to a list of `backtrace-frame' +objects (`backtrace-get-frames' is provided for that purpose, if +desired), and may optionally modify `backtrace-view', which is a +plist describing the appearance of the backtrace. Finally, it +should call `backtrace-print'. + +`backtrace-print' calls `backtrace-insert-header-function' +followed by `backtrace-print-frame', once for each stack frame." + :syntax-table emacs-lisp-mode-syntax-table + (when backtrace-fontify + (setq font-lock-defaults + '((backtrace-font-lock-keywords + backtrace-font-lock-keywords-1 + backtrace-font-lock-keywords-2) + nil nil nil nil + (font-lock-syntactic-face-function + . lisp-font-lock-syntactic-face-function)))) + (setq truncate-lines t) + (buffer-disable-undo) + ;; In debug.el, from 1998 to 2009 this was set to nil, reason stated + ;; was because of bytecode. Since 2009 it's been set to t, but the + ;; default is t so I think this isn't necessary. + ;; (set-buffer-multibyte t) + (setq-local revert-buffer-function #'backtrace-revert) + (setq-local filter-buffer-substring-function #'backtrace--filter-visible) + (setq-local indent-line-function 'lisp-indent-line) + (setq-local indent-region-function 'lisp-indent-region) + (add-hook 'xref-backend-functions #'backtrace--xref-backend nil t)) + +(put 'backtrace-mode 'mode-class 'special) + +;;; Backtrace printing + +;;;###autoload +(defun backtrace () + "Print a trace of Lisp function calls currently active. +Output stream used is value of `standard-output'." + (princ (backtrace-to-string (backtrace-get-frames 'backtrace))) + nil) + +(defun backtrace-to-string(&optional frames) + "Format FRAMES, a list of `backtrace-frame' objects, for output. +Return the result as a string. If FRAMES is nil, use all +function calls currently active." + (unless frames (setq frames (backtrace-get-frames 'backtrace-to-string))) + (let ((backtrace-fontify nil)) + (with-temp-buffer + (backtrace-mode) + (setq backtrace-view '(:show-flags t) + backtrace-frames frames + backtrace-print-function #'cl-prin1) + (backtrace-print) + (substring-no-properties (filter-buffer-substring (point-min) + (point-max)))))) + +(provide 'backtrace) + +;;; backtrace.el ends here |