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Support loading so-long.el on top of an earlier version

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* so-long.el (so-long-version, so-long--latest-version): New variables.

This enables users to safely load version 1.0 of so-long.el on top of
an earlier version, as well as making provisions for doing likewise
following any incompatible changes arising in future versions.
This commit is contained in:
Phil Sainty 2019-10-22 00:05:50 +13:00
parent b28f35ac65
commit a94f961e62
1 changed files with 50 additions and 0 deletions
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50
lisp/so-long.el
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@ -411,6 +411,8 @@
(add-to-list 'customize-package-emacs-version-alist
'(so-long ("1.0" . "27.1")))
(defconst so-long--latest-version "1.0")
(declare-function longlines-mode "longlines")
(defvar longlines-mode)
@ -1818,6 +1820,54 @@ If it appears in `%s', you should remove it."
(cdr hookfunc)))
(make-obsolete (car hookfunc) nil "so-long.el version 1.0")))
;; Live upgrades, for when a newer version is loaded over an older one.
;;
;; If `so-long-version' was already bound then that tells us which version we
;; should upgrade from. If `so-long-version' is unbound then most likely there
;; was no older version loaded; however, prior to version 1.0 `so-long-version'
;; was not defined at all, and so we also need to detect that scenario, which
;; we can do by testing for the presence of a symbol which was removed in 1.0.
;;
;; The variable `so-long-mode-enabled' covers versions 0.5 - 0.7.6, which is
;; every pre-1.0 release using the name "so-long.el".
(defvar so-long-version (if (boundp 'so-long-mode-enabled)
"0.5" ;; >= 0.5 and < 1.0
so-long--latest-version)
"The loaded version of so-long.el.")
;; Version-specific updates.
(when (version< so-long-version so-long--latest-version)
;; Perform each update in sequence, as necessary.
;; Update to version 1.0 from earlier versions:
(when (version< so-long-version "1.0")
(remove-hook 'change-major-mode-hook 'so-long-change-major-mode)
(require 'advice)
(when (ad-find-advice 'hack-local-variables 'after 'so-long--file-local-mode)
(ad-remove-advice 'hack-local-variables 'after 'so-long--file-local-mode)
(ad-activate 'hack-local-variables))
(when (ad-find-advice 'set-auto-mode 'around 'so-long--set-auto-mode)
(ad-remove-advice 'set-auto-mode 'around 'so-long--set-auto-mode)
(ad-activate 'set-auto-mode))
(when (boundp 'so-long-mode-map)
(define-key so-long-mode-map [remap so-long-mode-revert] #'so-long-revert))
(dolist (var '(so-long-mode--inhibited
so-long-original-mode))
(makunbound var))
(dolist (func '(so-long-change-major-mode
so-long-check-header-modes
so-long-line-detected-p))
(fmakunbound func))
(defvar so-long-mode-enabled)
(when so-long-mode-enabled
(unless global-so-long-mode
(global-so-long-mode 1)))
(makunbound 'so-long-mode-enabled))
;; Update to version 1.N:
;; (when (version< so-long-version "1.N") ...)
;;
;; All updates completed.
(setq so-long-version so-long--latest-version))
(provide 'so-long)