Installing a package via `package-install' in Lisp?

Question

The documentation of package-install says: "Install the package PKG. PKG can be [...] a symbol naming one of the available packages in an archive in ‘package-archives’."

To install the latest version of Aggressive Indent Mode, I have tried:

(package-install 'aggressive-indent-1.8.3)
(package-install 'aggressive-indent-1.8.3.el)

But both of them make Emacs drop into the Lisp debugger. I cannot use simply:

(package-install 'aggressive-indent)

which would work, because I already have an older version of Aggressive Indent Mode installed.

Answer 1

The symbols that name packages are just the name, and don't include version numbers or extensions, so that's not surprising.

Upgrades happen by first uninstalling the package and then downloading and installing the new version. You could check to see what version is installed, and if it's too old uninstall it and install the latest version.