emacs: Add shell completions for "guix" command.

Suggested by Ludovic Courtès <ludo@gnu.org>.

* emacs/guix-pcomplete.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Completions): New node.

3 files changed, 425 insertions, 0 deletions

diff --git a/doc/emacs.texi b/doc/emacs.texi
index 6c1b255af0..00cd5c1396 100644
--- a/doc/emacs.texi
+++ b/doc/emacs.texi
@@ -19,6 +19,7 @@ guix package}).  Specifically, ``guix.el'' makes it easy to:
 * Usage: Emacs Usage.			Using the interface.
 * Configuration: Emacs Configuration.	Configuring the interface.
 * Prettify Mode: Emacs Prettify.	Abbreviating @file{/gnu/store/@dots{}} file names.
+* Completions: Emacs Completions.       Completing @command{guix} shell command.
 @end menu
 
 @node Emacs Initial Setup
@@ -489,3 +490,34 @@ mode hooks (@pxref{Hooks,,, emacs, The GNU Emacs Manual}), for example:
 (add-hook 'shell-mode-hook 'guix-prettify-mode)
 (add-hook 'dired-mode-hook 'guix-prettify-mode)
 @end example
+
+
+@node Emacs Completions
+@subsection Shell Completions
+
+Another feature that becomes available after configuring Emacs interface
+(@pxref{Emacs Initial Setup}) is completing of @command{guix}
+subcommands, options, packages and other things in @code{shell}
+(@pxref{Interactive Shell,,, emacs, The GNU Emacs Manual}) and
+@code{eshell} (@pxref{Top,,, eshell, Eshell: The Emacs Shell}).
+
+It works the same way as other completions do.  Just press @key{TAB}
+when your intuition tells you.
+
+And here are some examples, where pressing @key{TAB} may complete
+something:
+
+@itemize @w{}
+
+@item @code{guix pa}@key{TAB}
+@item @code{guix package -}@key{TAB}
+@item @code{guix package --}@key{TAB}
+@item @code{guix package -i gei}@key{TAB}
+@item @code{guix build -L/tm}@key{TAB}
+@item @code{guix build --sy}@key{TAB}
+@item @code{guix build --system=i}@key{TAB}
+@item @code{guix system rec}@key{TAB}
+@item @code{guix lint --checkers=sy}@key{TAB}
+@item @code{guix lint --checkers=synopsis,des}@key{TAB}
+
+@end itemize
diff --git a/emacs.am b/emacs.am
index a43168e2cf..372b33e822 100644
--- a/emacs.am
+++ b/emacs.am
@@ -26,6 +26,7 @@ ELFILES =					\
   emacs/guix-info.el				\
   emacs/guix-list.el				\
   emacs/guix-messages.el			\
+  emacs/guix-pcomplete.el			\
   emacs/guix-prettify.el			\
   emacs/guix-utils.el				\
   emacs/guix.el
diff --git a/emacs/guix-pcomplete.el b/emacs/guix-pcomplete.el
new file mode 100644
index 0000000000..fa71dd5e21
--- /dev/null
+++ b/emacs/guix-pcomplete.el
@@ -0,0 +1,392 @@
+;;; guix-pcomplete.el --- Functions for completing guix commands  -*- 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 completions for "guix" command that may be used in
+;; `shell', `eshell' and wherever `pcomplete' works.
+
+;;; Code:
+
+(require 'pcomplete)
+(require 'pcmpl-unix)
+(require 'cl-lib)
+(require 'guix-utils)
+
+
+;;; Regexps for parsing various "guix ..." outputs
+
+(defvar guix-pcomplete-parse-package-regexp
+  (rx bol (group (one-or-more (not blank))))
+  "Regexp used to find names of the packages.")
+
+(defvar guix-pcomplete-parse-command-regexp
+  (rx bol "   "
+      (group wordchar (one-or-more (or wordchar "-"))))
+  "Regexp used to find guix commands.
+'Command' means any option not prefixed with '-'.  For example,
+guix subcommand, system action, importer, etc.")
+
+(defvar guix-pcomplete-parse-long-option-regexp
+  (rx (or "  " ", ")
+      (group "--" (one-or-more (or wordchar "-"))
+             (zero-or-one "=")))
+  "Regexp used to find long options.")
+
+(defvar guix-pcomplete-parse-short-option-regexp
+  (rx bol (one-or-more blank)
+      "-" (group (not (any "- "))))
+  "Regexp used to find short options.")
+
+(defvar guix-pcomplete-parse-linter-regexp
+  (rx bol "- " (group (one-or-more (or wordchar "-"))))
+  "Regexp used to find 'lint' checkers.")
+
+(defvar guix-pcomplete-parse-regexp-group 1
+  "Parenthesized expression of regexps used to find commands and
+options.")
+
+
+;;; Non-receivable completions
+
+(defvar guix-pcomplete-systems
+  '("x86_64-linux" "i686-linux" "armhf-linux" "mips64el-linux")
+  "List of supported systems.")
+
+(defvar guix-pcomplete-hash-formats
+  '("nix-base32" "base32" "base16" "hex" "hexadecimal")
+  "List of supported hash formats.")
+
+(defvar guix-pcomplete-refresh-subsets
+  '("core" "non-core")
+  "List of supported 'refresh' subsets.")
+
+(defvar guix-pcomplete-key-policies
+  '("interactive" "always" "never")
+  "List of supported key download policies.")
+
+
+;;; Interacting with guix
+
+(defcustom guix-pcomplete-guix-program (executable-find "guix")
+  "Name of the 'guix' program.
+It is used to find guix commands, options, packages, etc."
+  :type 'file
+  :group 'pcomplete
+  :group 'guix)
+
+(defun guix-pcomplete-run-guix (&rest args)
+  "Run `guix-pcomplete-guix-program' with ARGS.
+Insert the output to the current buffer."
+  (apply #'call-process
+         guix-pcomplete-guix-program nil t nil args))
+
+(defun guix-pcomplete-run-guix-and-search (regexp &optional group
+                                                  &rest args)
+  "Run `guix-pcomplete-guix-program' with ARGS and search for matches.
+Return a list of strings matching REGEXP.
+GROUP specifies a parenthesized expression used in REGEXP."
+  (with-temp-buffer
+    (apply #'guix-pcomplete-run-guix args)
+    (goto-char (point-min))
+    (let (result)
+      (while (re-search-forward regexp nil t)
+        (push (match-string-no-properties group) result))
+      (nreverse result))))
+
+(defmacro guix-pcomplete-define-options-finder (name docstring regexp
+                                                     &optional filter)
+  "Define function NAME to receive guix options and commands.
+
+The defined function takes an optional COMMAND argument.  This
+function will run 'guix COMMAND --help' (or 'guix --help' if
+COMMAND is nil) using `guix-pcomplete-run-guix-and-search' and
+return its result.
+
+If FILTER is specified, it should be a function.  The result is
+passed to this FILTER as argument and the result value of this
+function call is returned."
+  (declare (doc-string 2) (indent 1))
+  `(guix-memoized-defun ,name (&optional command)
+     ,docstring
+     (let* ((args '("--help"))
+            (args (if command (cons command args) args))
+            (res (apply #'guix-pcomplete-run-guix-and-search
+                        ,regexp guix-pcomplete-parse-regexp-group args)))
+       ,(if filter
+            `(funcall ,filter res)
+          'res))))
+
+(guix-pcomplete-define-options-finder guix-pcomplete-commands
+  "If COMMAND is nil, return a list of available guix commands.
+If COMMAND is non-nil (it should be a string), return available
+subcommands, actions, etc. for this guix COMMAND."
+  guix-pcomplete-parse-command-regexp)
+
+(guix-pcomplete-define-options-finder guix-pcomplete-long-options
+  "Return a list of available long options for guix COMMAND."
+  guix-pcomplete-parse-long-option-regexp)
+
+(guix-pcomplete-define-options-finder guix-pcomplete-short-options
+  "Return a string with available short options for guix COMMAND."
+  guix-pcomplete-parse-short-option-regexp
+  (lambda (list)
+    (mapconcat #'identity list "")))
+
+(guix-memoized-defun guix-pcomplete-all-packages ()
+  "Return a list of all available Guix packages."
+  (guix-pcomplete-run-guix-and-search
+   guix-pcomplete-parse-package-regexp
+   guix-pcomplete-parse-regexp-group
+   "package" "--list-available"))
+
+(guix-memoized-defun guix-pcomplete-installed-packages (&optional profile)
+  "Return a list of Guix packages installed in PROFILE."
+  (let* ((args (and profile
+                    (list (concat "--profile=" profile))))
+         (args (append '("package" "--list-installed") args)))
+    (apply #'guix-pcomplete-run-guix-and-search
+           guix-pcomplete-parse-package-regexp
+           guix-pcomplete-parse-regexp-group
+           args)))
+
+(guix-memoized-defun guix-pcomplete-lint-checkers ()
+  "Return a list of all available lint checkers."
+  (guix-pcomplete-run-guix-and-search
+   guix-pcomplete-parse-linter-regexp
+   guix-pcomplete-parse-regexp-group
+   "lint" "--list-checkers"))
+
+
+;;; Completing
+
+(defvar guix-pcomplete-option-regexp (rx string-start "-")
+  "Regexp to match an option.")
+
+(defvar guix-pcomplete-long-option-regexp (rx string-start "--")
+  "Regexp to match a long option.")
+
+(defvar guix-pcomplete-long-option-with-arg-regexp
+  (rx string-start
+      (group "--" (one-or-more any)) "="
+      (group (zero-or-more any)))
+  "Regexp to match a long option with its argument.
+The first parenthesized group defines the option and the second
+group - the argument.")
+
+(defvar guix-pcomplete-short-option-with-arg-regexp
+  (rx string-start
+      (group "-" (not (any "-")))
+      (group (zero-or-more any)))
+  "Regexp to match a short option with its argument.
+The first parenthesized group defines the option and the second
+group - the argument.")
+
+(defun guix-pcomplete-match-option ()
+  "Return non-nil, if the current argument is an option."
+  (pcomplete-match guix-pcomplete-option-regexp 0))
+
+(defun guix-pcomplete-match-long-option ()
+  "Return non-nil, if the current argument is a long option."
+  (pcomplete-match guix-pcomplete-long-option-regexp 0))
+
+(defun guix-pcomplete-match-long-option-with-arg ()
+  "Return non-nil, if the current argument is a long option with value."
+  (pcomplete-match guix-pcomplete-long-option-with-arg-regexp 0))
+
+(defun guix-pcomplete-match-short-option-with-arg ()
+  "Return non-nil, if the current argument is a short option with value."
+  (pcomplete-match guix-pcomplete-short-option-with-arg-regexp 0))
+
+(defun guix-pcomplete-long-option-arg (option args)
+  "Return a long OPTION's argument from a list of arguments ARGS."
+  (let* ((re (concat "\\`" option "=\\(.*\\)"))
+         (args (cl-member-if (lambda (arg)
+                               (string-match re arg))
+                             args))
+         (cur (car args)))
+    (when cur
+      (match-string-no-properties 1 cur))))
+
+(defun guix-pcomplete-short-option-arg (option args)
+  "Return a short OPTION's argument from a list of arguments ARGS."
+  (let* ((re (concat "\\`" option "\\(.*\\)"))
+         (args (cl-member-if (lambda (arg)
+                               (string-match re arg))
+                             args))
+         (cur (car args)))
+    (when cur
+      (let ((arg (match-string-no-properties 1 cur)))
+        (if (string= "" arg)
+            (cadr args)                 ; take the next arg
+          arg)))))
+
+(defun guix-pcomplete-complete-comma-args (entries)
+  "Complete comma separated arguments using ENTRIES."
+  (let ((index pcomplete-index))
+    (while (= index pcomplete-index)
+      (let* ((args (if (or (guix-pcomplete-match-long-option-with-arg)
+                           (guix-pcomplete-match-short-option-with-arg))
+                       (pcomplete-match-string 2 0)
+                     (pcomplete-arg 0)))
+             (input (if (string-match ".*,\\(.*\\)" args)
+                        (match-string-no-properties 1 args)
+                      args)))
+        (pcomplete-here* entries input)))))
+
+(defun guix-pcomplete-complete-command-arg (command)
+  "Complete argument for guix COMMAND."
+  (cond
+   ((member command
+            '("archive" "build" "environment" "lint" "refresh"))
+    (while t
+      (pcomplete-here (guix-pcomplete-all-packages))))
+   (t (pcomplete-here* (pcomplete-entries)))))
+
+(defun guix-pcomplete-complete-option-arg (command option &optional input)
+  "Complete argument for COMMAND's OPTION.
+INPUT is the current partially completed string."
+  (cl-flet ((option? (short long)
+              (or (string= option short)
+                  (string= option long)))
+            (command? (&rest commands)
+              (member command commands))
+            (complete (entries)
+              (pcomplete-here entries input nil t))
+            (complete* (entries)
+              (pcomplete-here* entries input t)))
+    (cond
+     ((option? "-L" "--load-path")
+      (complete* (pcomplete-dirs)))
+     ((string= "--key-download" option)
+      (complete* guix-pcomplete-key-policies))
+
+     ((command? "package")
+      (cond
+       ;; For '--install[=]' and '--remove[=]', try to complete a package
+       ;; name (INPUT) after the "=" sign, and then the rest packages
+       ;; separated with spaces.
+       ((option? "-i" "--install")
+        (complete (guix-pcomplete-all-packages))
+        (while (not (guix-pcomplete-match-option))
+          (pcomplete-here (guix-pcomplete-all-packages))))
+       ((option? "-r" "--remove")
+        (let* ((profile (or (guix-pcomplete-short-option-arg
+                             "-p" pcomplete-args)
+                            (guix-pcomplete-long-option-arg
+                             "--profile" pcomplete-args)))
+               (profile (and profile (expand-file-name profile))))
+          (complete (guix-pcomplete-installed-packages profile))
+          (while (not (guix-pcomplete-match-option))
+            (pcomplete-here (guix-pcomplete-installed-packages profile)))))
+       ((string= "--show" option)
+        (complete (guix-pcomplete-all-packages)))
+       ((option? "-p" "--profile")
+        (complete* (pcomplete-dirs)))
+       ((option? "-m" "--manifest")
+        (complete* (pcomplete-entries)))))
+
+     ((and (command? "archive" "build")
+           (option? "-s" "--system"))
+      (complete* guix-pcomplete-systems))
+
+     ((and (command? "build")
+           (option? "-r" "--root"))
+      (complete* (pcomplete-entries)))
+
+     ((and (command? "environment")
+           (option? "-l" "--load"))
+      (complete* (pcomplete-entries)))
+
+     ((and (command? "hash" "download")
+           (option? "-f" "--format"))
+      (complete* guix-pcomplete-hash-formats))
+
+     ((and (command? "lint")
+           (option? "-c" "--checkers"))
+      (guix-pcomplete-complete-comma-args
+       (guix-pcomplete-lint-checkers)))
+
+     ((and (command? "publish")
+           (option? "-u" "--user"))
+      (complete* (pcmpl-unix-user-names)))
+
+     ((and (command? "refresh")
+           (option? "-s" "--select"))
+      (complete* guix-pcomplete-refresh-subsets)))))
+
+(defun guix-pcomplete-complete-options (command)
+  "Complete options (with their arguments) for guix COMMAND."
+  (while (guix-pcomplete-match-option)
+    (let ((index pcomplete-index))
+      (if (guix-pcomplete-match-long-option)
+
+          ;; Long options.
+          (if (guix-pcomplete-match-long-option-with-arg)
+              (let ((option (pcomplete-match-string 1 0))
+                    (arg    (pcomplete-match-string 2 0)))
+                (guix-pcomplete-complete-option-arg
+                 command option arg))
+
+            (pcomplete-here* (guix-pcomplete-long-options command))
+            ;; We support '--opt arg' style (along with '--opt=arg'),
+            ;; because 'guix package --install/--remove' may be used this
+            ;; way.  So try to complete an argument after the option has
+            ;; been completed.
+            (unless (guix-pcomplete-match-option)
+              (guix-pcomplete-complete-option-arg
+               command (pcomplete-arg 0 -1))))
+
+        ;; Short options.
+        (let ((arg (pcomplete-arg 0)))
+          (if (> (length arg) 2)
+              ;; Support specifying an argument after a short option without
+              ;; spaces (for example, '-L/tmp/foo').
+              (guix-pcomplete-complete-option-arg
+               command
+               (substring-no-properties arg 0 2)
+               (substring-no-properties arg 2))
+            (pcomplete-opt (guix-pcomplete-short-options command))
+            (guix-pcomplete-complete-option-arg
+             command (pcomplete-arg 0 -1)))))
+
+      ;; If there were no completions, move to the next argument and get
+      ;; out if the last argument is achieved.
+      (when (= index pcomplete-index)
+        (if (= pcomplete-index pcomplete-last)
+            (throw 'pcompleted nil)
+          (pcomplete-next-arg))))))
+
+;;;###autoload
+(defun pcomplete/guix ()
+  "Completion for `guix'."
+  (let ((commands (guix-pcomplete-commands)))
+    (pcomplete-here* (cons "--help" commands))
+    (let ((command (pcomplete-arg 'first 1)))
+      (when (member command commands)
+        (guix-pcomplete-complete-options command)
+        (let ((subcommands (guix-pcomplete-commands command)))
+          (when subcommands
+            (pcomplete-here* subcommands)))
+        (guix-pcomplete-complete-options command)
+        (guix-pcomplete-complete-command-arg command)))))
+
+(provide 'guix-pcomplete)
+
+;;; guix-pcomplete.el ends here