emacs: Add modes for viewing build logs.

* emacs/guix-build-log.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Build Log): Document it.  New node.
  (Emacs Interface): Add it.
* doc/guix.texi (Top): Likewise.

doc/emacs.texi

@@ -11,6 +11,7 @@ Guix convenient and fun.
 * Package Management: Emacs Package Management.	Managing packages and generations.
 * Popup Interface: Emacs Popup Interface.	Magit-like interface for guix commands.
 * Prettify Mode: Emacs Prettify.	Abbreviating @file{/gnu/store/@dots{}} file names.
+* Build Log Mode: Emacs Build Log.	Highlighting Guix build logs.
 * Completions: Emacs Completions.       Completing @command{guix} shell command.
 @end menu
 
@@ -571,6 +572,36 @@ mode hooks (@pxref{Hooks,,, emacs, The GNU Emacs Manual}), for example:
 @end example
 
 
+@node Emacs Build Log
+@section Build Log Mode
+
+GNU@tie{}Guix provides major and minor modes for highlighting build
+logs.  So when you have a file with a package build output---for
+example, a file returned by @command{guix build --log-file @dots{}}
+command (@pxref{Invoking guix build}), you may call @kbd{M-x
+guix-build-log-mode} command in the buffer with this file.  This major
+mode highlights some lines specific to build output and provides the
+following key bindings:
+
+@table @kbd
+
+@item M-n
+Move to the next build phase.
+
+@item M-p
+Move to the previous build phase.
+
+@end table
+
+There is also @kbd{M-x guix-build-log-minor-mode} which also provides
+the same highlighting (but not key bindings).  And as it is a minor
+mode, it can be enabled in any buffer.  For example, if you are building
+some package in a shell buffer (@pxref{Interactive Shell,,, emacs, The
+GNU Emacs Manual}), you may enable @command{guix-build-log-minor-mode}
+to make it more colorful.  Guix build output is rather specific, so this
+new highlighting shouldn't conflict with the existing one.
+
+
 @node Emacs Completions
 @section Shell Completions
 

doc/guix.texi

@@ -114,6 +114,7 @@ Emacs Interface
 * Package Management: Emacs Package Management.	Managing packages and generations.
 * Popup Interface: Emacs Popup Interface.	Magit-like interface for guix commands.
 * Prettify Mode: Emacs Prettify.	Abbreviating @file{/gnu/store/@dots{}} file names.
+* Build Log Mode: Emacs Build Log.	Highlighting Guix build logs.
 * Completions: Emacs Completions.       Completing @command{guix} shell command.
 
 Programming Interface

emacs.am

@@ -21,6 +21,7 @@ AUTOLOADS = emacs/guix-autoloads.el
 ELFILES =					\
   emacs/guix-backend.el				\
   emacs/guix-base.el				\
+  emacs/guix-build-log.el			\
   emacs/guix-command.el				\
   emacs/guix-emacs.el				\
   emacs/guix-external.el			\

emacs/guix-build-log.el

+;;; guix-build-log.el --- Major and minor modes for build logs   -*- lexical-binding: t -*-
+
+;; Copyright © 2015 Alex Kost <alezost@gmail.com>
+
+;; This file is part of GNU Guix.
+
+;; GNU Guix 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 Guix 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This file provides a major mode (`guix-build-log-mode') and a minor mode
+;; (`guix-build-log-minor-mode') for highlighting Guix build logs.
+
+;;; Code:
+
+(defgroup guix-build-log nil
+  "Settings for `guix-build-log-mode'."
+  :group 'guix)
+
+(defgroup guix-build-log-faces nil
+  "Faces for `guix-build-log-mode'."
+  :group 'guix-build-log
+  :group 'guix-faces)
+
+(defface guix-build-log-title-head
+  '((t :inherit font-lock-keyword-face))
+  "Face for '@' symbol of a log title."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-title-start
+  '((t :inherit guix-build-log-title-head))
+  "Face for a log title denoting a start of a process."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-title-success
+  '((t :inherit guix-build-log-title-head))
+  "Face for a log title denoting a successful end of a process."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-title-fail
+  '((t :inherit error))
+  "Face for a log title denoting a failed end of a process."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-title-end
+  '((t :inherit guix-build-log-title-head))
+  "Face for a log title denoting an undefined end of a process."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-name
+  '((t :inherit font-lock-function-name-face))
+  "Face for a phase name."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-start
+  '((default :weight bold)
+    (((class grayscale) (background light)) :foreground "Gray90")
+    (((class grayscale) (background dark))  :foreground "DimGray")
+    (((class color) (min-colors 16) (background light))
+     :foreground "DarkGreen")
+    (((class color) (min-colors 16) (background dark))
+     :foreground "LimeGreen")
+    (((class color) (min-colors 8)) :foreground "green"))
+  "Face for the start line of a phase."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-end
+  '((((class grayscale) (background light)) :foreground "Gray90")
+    (((class grayscale) (background dark))  :foreground "DimGray")
+    (((class color) (min-colors 16) (background light))
+     :foreground "ForestGreen")
+    (((class color) (min-colors 16) (background dark))
+     :foreground "LightGreen")
+    (((class color) (min-colors 8)) :foreground "green")
+    (t :weight bold))
+  "Face for the end line of a phase."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-success
+  '((t))
+  "Face for the 'succeeded' word of a phase line."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-fail
+  '((t :inherit error))
+  "Face for the 'failed' word of a phase line."
+  :group 'guix-build-log-faces)
+
+(defface guix-build-log-phase-seconds
+  '((t :inherit font-lock-constant-face))
+  "Face for the number of seconds for a phase."
+  :group 'guix-build-log-faces)
+
+(defcustom guix-build-log-mode-hook
+  ;; Not using `compilation-minor-mode' because it rebinds some standard
+  ;; keys, including M-n/M-p.
+  '(compilation-shell-minor-mode view-mode)
+  "Hook run after `guix-build-log-mode' is entered."
+  :type 'hook
+  :group 'guix-build-log)
+
+(defvar guix-build-log-phase-name-regexp "`\\([^']+\\)'"
+  "Regexp for a phase name.")
+
+(defvar guix-build-log-phase-start-regexp
+  (concat "^starting phase " guix-build-log-phase-name-regexp)
+  "Regexp for the start line of a 'build' phase.")
+
+(defun guix-build-log-title-regexp (&optional state)
+  "Return regexp for the log title.
+STATE is a symbol denoting a state of the title.  It should be
+`start', `fail', `success' or `nil' (for a regexp matching any
+state)."
+  (let* ((word-rx (rx (1+ (any word "-"))))
+         (state-rx (cond ((eq state 'start)   (concat word-rx "started"))
+                         ((eq state 'success) (concat word-rx "succeeded"))
+                         ((eq state 'fail)    (concat word-rx "failed"))
+                         (t word-rx))))
+    (rx-to-string
+     `(and bol (group "@") " " (group (regexp ,state-rx)))
+     t)))
+
+(defun guix-build-log-phase-end-regexp (&optional state)
+  "Return regexp for the end line of a 'build' phase.
+STATE is a symbol denoting how a build phase was ended.  It should be
+`fail', `success' or `nil' (for a regexp matching any state)."
+  (let ((state-rx (cond ((eq state 'success) "succeeded")
+                        ((eq state 'fail)    "failed")
+                        (t (regexp-opt '("succeeded" "failed"))))))
+    (rx-to-string
+     `(and bol "phase " (regexp ,guix-build-log-phase-name-regexp)
+           " " (group (regexp ,state-rx)) " after "
+           (group (1+ digit)) " seconds")
+     t)))
+
+(defvar guix-build-log-font-lock-keywords
+  `((,(guix-build-log-title-regexp 'start)
+     (1 'guix-build-log-title-head)
+     (2 'guix-build-log-title-start))
+    (,(guix-build-log-title-regexp 'success)
+     (1 'guix-build-log-title-head)
+     (2 'guix-build-log-title-success))
+    (,(guix-build-log-title-regexp 'fail)
+     (1 'guix-build-log-title-head)
+     (2 'guix-build-log-title-fail))
+    (,(guix-build-log-title-regexp)
+     (1 'guix-build-log-title-head)
+     (2 'guix-build-log-title-end))
+    (,guix-build-log-phase-start-regexp
+     (0 'guix-build-log-phase-start)
+     (1 'guix-build-log-phase-name prepend))
+    (,(guix-build-log-phase-end-regexp 'success)
+     (0 'guix-build-log-phase-end)
+     (1 'guix-build-log-phase-name prepend)
+     (2 'guix-build-log-phase-success prepend)
+     (3 'guix-build-log-phase-seconds prepend))
+    (,(guix-build-log-phase-end-regexp 'fail)
+     (0 'guix-build-log-phase-end)
+     (1 'guix-build-log-phase-name prepend)
+     (2 'guix-build-log-phase-fail prepend)
+     (3 'guix-build-log-phase-seconds prepend)))
+  "A list of `font-lock-keywords' for `guix-build-log-mode'.")
+
+(defvar guix-build-log-mode-map
+  (let ((map (make-sparse-keymap)))
+    (set-keymap-parent map special-mode-map)
+    (define-key map (kbd "M-n") 'guix-build-log-next-phase)
+    (define-key map (kbd "M-p") 'guix-build-log-previous-phase)
+    map)
+  "Keymap for `guix-build-log-mode' buffers.")
+
+(defun guix-build-log-next-phase (&optional arg)
+  "Move to the next build phase.
+With ARG, do it that many times.  Negative ARG means move
+backward."
+  (interactive "^p")
+  (if arg
+      (when (zerop arg) (user-error "Try again"))
+    (setq arg 1))
+  (let ((search-fun (if (> arg 0)
+                        #'re-search-forward
+                      #'re-search-backward))
+        (n (abs arg))
+        found last-found)
+    (save-excursion
+      (end-of-line (if (> arg 0) 1 0))  ; skip the current line
+      (while (and (not (zerop n))
+                  (setq found
+                        (funcall search-fun
+                                 guix-build-log-phase-start-regexp
+                                 nil t)))
+        (setq n (1- n)
+              last-found found)))
+    (when last-found
+      (goto-char last-found)
+      (forward-line 0))
+    (or found
+        (user-error (if (> arg 0)
+                        "No next build phase"
+                      "No previous build phase")))))
+
+(defun guix-build-log-previous-phase (&optional arg)
+  "Move to the previous build phase.
+With ARG, do it that many times.  Negative ARG means move
+forward."
+  (interactive "^p")
+  (guix-build-log-next-phase (- (or arg 1))))
+
+;;;###autoload
+(define-derived-mode guix-build-log-mode special-mode
+  "Guix-Build-Log"
+  "Major mode for viewing Guix build logs.
+
+\\{guix-build-log-mode-map}"
+  (setq font-lock-defaults '(guix-build-log-font-lock-keywords t)))
+
+;;;###autoload
+(define-minor-mode guix-build-log-minor-mode
+  "Toggle Guix Build Log minor mode.
+
+With a prefix argument ARG, enable Guix Build Log minor mode if
+ARG is positive, and disable it otherwise.  If called from Lisp,
+enable the mode if ARG is omitted or nil.
+
+When Guix Build Log minor mode is enabled, it highlights build
+log in the current buffer.  This mode can be enabled
+programmatically using hooks:
+
+  (add-hook 'shell-mode-hook 'guix-build-log-minor-mode)"
+  :init-value nil
+  :lighter " Guix-Build-Log"
+  :group 'guix-build-log
+  (if guix-build-log-minor-mode
+      (font-lock-add-keywords nil guix-build-log-font-lock-keywords)
+    (font-lock-remove-keywords nil guix-build-log-font-lock-keywords))
+  (when font-lock-mode
+    (font-lock-fontify-buffer)))
+
+(provide 'guix-build-log)
+
+;;; guix-build-log.el ends here