jus want to state the obvious here in case it is useful [but everybody probbly lready knows] --- not everybody uses packages or maybe trusts them has internet etc.
On 2/5/22, João Pedro de Amorim Paula <jpedrodeamo...@gmail.com> wrote: > On 04 February 2022 08:30, Tim Cross <theophil...@gmail.com> wrote: > >> I'm assuming it is, but I have to admit I'm still not 100% clear on >> how Emacs handles the situation where you use a library that is both >> built-in and available in ELPA. Does Emacs use the latest version >> available or does it use the built-in version until you explicitly >> select the ELPA versions? > > Welp, I happened to ponder the same question after trying to implement a > function to install packages that are not installed already (I'm not > using any helper configuration such as use-package, which would already > handle this). From what I gathered empirically, it appears that if > something is built-in, Emacs' package.el won't try to install -- it > checks with package-installed-p on any call to package-install, which > checks if the package is built-in with package-built-in-p as a fallback > on cond --, but you can force installation from the archives by passing > a package description object (defined as package-desc on package.el) > instead of a symbol > > (let ((pkg-desc (assq 'org package-archive-contents))) > (package-install pkg-desc)) > > and Emacs seems to be loading the newest version when it is a dependency > of something else. Though I'm not really sure, as most of the packages I > have from ELPA have the same version as the ones built-in on Emacs > 28.0.91. I'll try and install Emacs 27 to check this out. > > In the mean time, I guess this would be a good opportunity to share a > couple of functions I have with the purpose of installing packages. > > (defun pkg-description (package) > "Return the description for PACKAGE. > If PACKAGE is installed, the will be present on `package-alist', > otherwise look for it in `package-archive-contents'." > (or (cadr (assoc package package-alist)) > (cadr (assoc package package-archive-contents)))) > > (defun pkg-ensure-archive (package) > "Install PACKAGE from the archives, if not already installed." > (when-let ((pkg-desc (pkg-description package))) > (unless (package-installed-p pkg-desc) > (package-install-from-archive pkg-desc)))) > > (defun require-package (package &optional force) > "Ensure that PACKAGE is installed. > If FORCE is non-nil, force installation regardless if PACKAGE is > built-in or not. > > First, use `package-installed-p' to check if PACKAGE was > installed via the Emacs package manager, otherwise, try to > `require' PACKAGE; this ensures that we don't require PACKAGE if > it was installed using the package manager. If both of those > fail, run `package-refresh-contents' and install PACKAGE." > (unless (and (not force) > (or (package-installed-p package) > (require package nil 'no-error))) > (unless (assoc package package-archive-contents) > (package-refresh-contents)) > (if force > (pkg-ensure-archive package) > (package-install package)))) > > On the last one, the main function that I use, if FORCE is non-nil it > will download and install the package from the archives even if it is > built-in. > > Best regards, > > -- > João Pedro de Amorim Paula > IT undergraduate at Universidade Federal do Rio Grande do Norte (UFRN) > -- The Kafka Pandemic A blog about science, health, human rights, and misopathy: https://thekafkapandemic.blogspot.com
