Related to #1313

As commented in the emacs ada-mode users list:

Thanks. Now, I am able to set it in this way:

alr config --set --global editor.cmd 'emacs
--eval=(ada-build-prompt-select-prj-file"${GPR_FILE}") ${GPR_FILE}'

Note that there is no space between the function and the string
argument. Otherwise, Alire splits the argument and Emacs is not able
to evaluate it correctly. Don't know if that could be considered a bug
in Alire or not, but I couldn't find a proper way to escape the space.

The space problem sounds like a bug, but it could be in your shell
rather than in Alire. It's simpler just to edit the alire config file
directly; it's ~/.config/alire/config.toml

When the config file is edited and space added:

$ alr edit
Editing crate with: ['emacs' '--eval=(ada-build-prompt-select-prj-file', '"play_2048.gpr")', 'play_2048.gpr']

And then Emacs errors:

command-line-1: End of file during parsing

That can be attributed to Alire, it's splitting the command assuming spaces as separator, so command lines containing spaces inside arguments are not supported. Using shell syntax (e.g. single quotes) inside the config file doesn't work either.

It's a very limited need and maybe difficult to solve it portably, but I think it deserves its own issue.