A Note On Straight.el's Transaction
By Anak Wannaphaschaiyong
This article is based on staright.el README which at the moment doesn’t have written document on how transaction works. So This is a work in progress until I either read straight.el codebase or summarize its documentation.
Conceptually, stright.el clones Git repo and them symlinking files into Emacs’s load path. A packages in straight.el is defined as recipe as a files which was symlinked together. I have an article on recipe.
straight.el runs straight-use-package during the Emacs initialization to check for package to be updated.
Now, straight has information of what package to be downloaded. user can choose to install whatever packages after Emacs has been launched.
straight.el introduce transaction concept which provide a way to keep track of things that happens when an operation is executed.
Packages in your emacs configuration (config.el?) are passed to straight-use-package to be managed. This process is done during loading of your init-file (init.el).
Note that there are two ways to load package into straight.el. First, straight.el is passed packages upon the loading init.el. The second way is when one want to try a package, so one decided to manually evaluate straight-use-package after emacs has been launched.
How can straight.el distinguish between the two?
straight.el determines whether packages is part of your init.el by reload init.el. This implies that straight.el should know when the file is evaluated. As of [2022-06-22 Wed], I think knowing when file is done evaluated is important because the following: imagine a scenario where package is loaded while init.el is evaluated, one can’t tell the name of packages that has been loaded after emacs initialized. One can take the approach of package.el by storing mutable state outside of config.el inside jk:package.el (which is loaded as part of emacs initialization), however, the main selling point of straight.el is be passed packages directly to staright-use-package while init.el is loaded.
straight.el has transaction system which can determine when init-file is finished loading by using post-command-hook which only execute code after interactive operation has finished. More abstractly, straight.el introduces transaction concept to keep track of an operation as a unit where, in this case, an operation is defined as evaluating a file.
staright.el will determine which and how to packages whenever straight-use-package is invoked. This is because internal state of straight.el is managed by straight-use-package and internal state can always be change when staright-use-package is invoked.