[ELPA] New package: package-fixes

[Artur Malabarba]

I've pushed some code to elpa.git (also below) for a package that should
fix a rather aggravating bug in package.el. Namely, that changing the
behaviour of macros (or even just defining new macros) can lead to bad
compilation issues during upgrades.
I'll bump its version to 0.1 (thus releasing it) if noone sees any issues.

This bug is fixed in emacs-25, package-fixes.el backports this fix to
Emacs 24.x. There will be plenty of users of Emacs 24.x for years to
come, so I wanted to provide packages with a way around this issue
(specially because some packages are already finding worryingly hacky
ways around it).

The goal here is that a package can add (package-fixes "0.1") to its
dependencies and rest assured that this bug won't happen anymore
(package-fixes.el does nothing if the user is running emacs-25).
This can futurely be used to fix new package.el bugs we encounter.


------------------------------
;;; package-fixes.el --- package.el bug fixes ported to older Emacsen  -*- 
lexical-binding: t; -*-

;; Copyright (C) 2015 Free Software Foundation, Inc.

;; Author: Artur Malabarba <address@hidden>
;; Keywords: tools
;; Version: 0

;; This program 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.

;; This program 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 package fixes some critical bugs in package.el 1.0.1 which
;; cause bad .elc files to be created during package upgrades when a
;; macro changes.  It is designed to be required as a dependency by
;; packages whose installation is affected by these bugs.

;; This package can be safely installed on Emacs >= 25, in which
;; case it does nothing.

;;; Code:


;;; Emacs < 25
(unless (fboundp 'package--list-loaded-files)
  (require 'package)
  (require 'find-func)

  (declare-function package-fixes--autoloads-file-name "package-fixes")
  (declare-function find-library-name "find-func")
  (declare-function package-fixes--list-loaded-files "package-fixes")
  (declare-function package-fixes--activate-autoloads-and-load-path 
"package-fixes")

  ;; None of these functions are defined in Emacs < 25.1.  Defining
  ;; them here doesn't actually do anything yet, they will be used by
  ;; the advices below.
  (defun package-fixes--autoloads-file-name (pkg-desc)
    "Return the absolute name of the autoloads file, sans extension.
PKG-DESC is a `package-desc' object."
    (expand-file-name
     (format "%s-autoloads" (package-desc-name pkg-desc))
     (package-desc-dir pkg-desc)))

  (defun package-fixes--activate-autoloads-and-load-path (pkg-desc)
    "Load the autoloads file and add package dir to `load-path'.
PKG-DESC is a `package-desc' object."
    (let* ((old-lp load-path)
           (pkg-dir (package-desc-dir pkg-desc))
           (pkg-dir-dir (file-name-as-directory pkg-dir)))
      (with-demoted-errors "Error loading autoloads: %s"
        (load (package-fixes--autoloads-file-name pkg-desc) nil t))
      (when (and (eq old-lp load-path)
                 (not (or (member pkg-dir load-path)
                          (member pkg-dir-dir load-path))))
        ;; Old packages don't add themselves to the `load-path', so we have to
        ;; do it ourselves.
        (push pkg-dir load-path))))

  (defun package-fixes--list-loaded-files (dir)
    "Recursively list all files in DIR which correspond to loaded features.
Returns the `file-name-sans-extension' of each file, relative to
DIR, sorted by most recently loaded last."
    (let* ((history (delq nil
                          (mapcar (lambda (x)
                                    (let ((f (car x)))
                                      (and f (file-name-sans-extension f))))
                                  load-history)))
           (dir (file-truename dir))
           ;; List all files that have already been loaded.
           (list-of-conflicts
            (delq
             nil
             (mapcar
              (lambda (x) (let* ((file (file-relative-name x dir))
                            ;; Previously loaded file, if any.
                            (previous
                             (ignore-errors
                               (file-name-sans-extension
                                (file-truename (find-library-name file)))))
                            (pos (when previous (member previous history))))
                       ;; Return (RELATIVE-FILENAME . HISTORY-POSITION)
                       (when pos
                         (cons (file-name-sans-extension file) (length pos)))))
              (directory-files-recursively dir "\\`[^\\.].*\\.el\\'")))))
      ;; Turn the list of (FILENAME . POS) back into a list of features.  Files 
in
      ;; subdirectories are returned relative to DIR (so not actually features).
      (let ((default-directory (file-name-as-directory dir)))
        (mapcar (lambda (x) (file-truename (car x)))
                (sort list-of-conflicts
                      ;; Sort the files by ascending HISTORY-POSITION.
                      (lambda (x y) (< (cdr x) (cdr y))))))))

  (defun package-fixes--load-files-for-activation (pkg-desc reload)
    "Load files for activating a package given by PKG-DESC.
Load the autoloads file, and ensure `load-path' is setup.  If
RELOAD is non-nil, also load all files in the package that
correspond to previously loaded files."
    (let* ((loaded-files-list (when reload
                                (package-fixes--list-loaded-files 
(package-desc-dir pkg-desc)))))
      ;; Add to load path, add autoloads, and activate the package.
      (package-fixes--activate-autoloads-and-load-path pkg-desc)
      ;; Call `load' on all files in `package-desc-dir' already present in
      ;; `load-history'.  This is done so that macros in these files are updated
      ;; to their new definitions.  If another package is being installed which
      ;; depends on this new definition, not doing this update would cause
      ;; compilation errors and break the installation.
      (with-demoted-errors "Error in package--load-files-for-activation: %s"
        (mapc (lambda (feature) (load feature nil t))
              ;; Skip autoloads file since we already evaluated it above.
              (remove (file-truename (package-fixes--autoloads-file-name 
pkg-desc))
                      loaded-files-list)))))

  
;;; 24.1, 24.2, 24.3
  (defadvice package--make-autoloads-and-compile (around 
fix-package--make-autoloads-and-compile
                                                         (name pkg-dir) 
activate)
    "Fixed `package--make-autoloads-and-compile'.
Behave the same as `package--make-autoloads-and-compile', except
it uses `package-fixes--load-files-for-activation' instead of just
loading the autoloads file."
    (package-generate-autoloads name pkg-dir)
    (package-fixes--load-files-for-activation pkg-desc :reload)
    (let ((load-path (cons pkg-dir load-path)))
      ;; We must load the autoloads file before byte compiling, in
      ;; case there are magic cookies to set up non-trivial paths.
      (byte-recompile-directory pkg-dir 0 t)))

;;; 24.4, 24.5
  (defadvice package--compile (after fix-package--compile (pkg-desc) activate)
    "Like `package--compile', but reload package first.
Uses `package-fixes--load-files-for-activation' to reload files."
    (package-activate-1 pkg-desc)
    (package-fixes--load-files-for-activation pkg-desc :reload)
    (byte-recompile-directory (package-desc-dir pkg-desc) 0 t)))

(provide 'package-fixes)
;;; package-fixes.el ends here