Thierry Volpiatto <thievol@posteo.net> writes:

> Philip Kaludercic <philipk@posteo.net> writes:
>
>> Philip Kaludercic <philipk@posteo.net> writes:
>>
>>>>>> It is used specially for reproducing bugs in a clean environment, see it
>>>>>> as emacs -Q for Emacs when reporting bugs. This script starts Emacs -Q
>>>>>> with only Helm loaded, this ensure the bug if one comes from Helm and
>>>>>> not another package. This is important especially nowaday people are
>>>>>> using "Emacs distribution" with the world list of packages installed.
>>>>>> Apart that the script is useful to quickly launch Emacs with helm, one
>>>>>> can use it from the Helm directory or symlinked to e.g. ~/bin. 
>>>>>
>>>>> I see.  In that case is there any reason you implement this as a shell
>>>>> script?
>>>>
>>>> Well when I wrote the script, packages where not existing and from
>>>> outside emacs it is actually the only way to run a package isolated.
>>>>
>>>>> (It might be interesting to provide something like this for
>>>>> package.el, to test packages in a generic way.)
>>>>
>>>> Yes, this would be interesting, it would be something like this:
>>>>
>>>> Emacs -Q
>>>> M-x <A command that run a package alone, isolated from other
>>>> packages nuisances>
>>>
>>> I was actually thinking of a command like
>>>
>>> M-x package-isolate RET foo,bar,baz RET
>>>
>>> and a new instance of Emacs using -Q is spun up, with all the packages
>>> you have listed loaded, and nothing else... Sounds like a fun little
>>> weekend project ;^)
>>
>> Here is my first attempt at providing this kind of a command.  Any
>> comments?
>
> Why not reusing package.el functions?
> Why do you want to start in an isolated elpa directory?
> Isn't something like this suffice? (just missing to fallback to CRM when
> helm is not available)

I don't know much about Helm, but does it not support CRM?

>     (defun package-isolate (packages)
>       "Start an uncustomised Emacs and only load a set of PACKAGES."
>       (interactive
>        (list (let ((helm-comp-read-use-marked t))
>                (completing-read "Packages: " (mapcar #'car (package--alist))))))

This doesn't allow selecting specific package versions, in case multiple
are installed (which might easily happen if you use package-vc).  I
stole the code in my patch from package-delete, and I guess it would be
possible to generalise it into a utility function.

>       (let* ((name (concat "package-isolate-" (mapconcat #'identity
>                                                          packages ",")))

This doesn't work, because the above returns a string, not a list of strings.

>              (deps (cl-loop for p in packages
>                             for sym = (intern p)
>                             append (package--dependencies sym))))
>         (apply #'start-process (concat "*" name "*") nil
>                (list (file-truename (expand-file-name invocation-name invocation-directory))
>                      "--quick" "--debug-init"
>                      (format "--eval=%S"
>                              `(progn
>                                (require 'warnings)
>                                (add-to-list 'warning-suppress-log-types 'initialization)
>                                (require 'package)
>                                (setq package-load-list
>                                 ',(append (mapcar (lambda (p) (list (intern p) t)) packages)
>                                           (mapcar (lambda (p) (list p t)) deps)))
>                                (package-initialize)))))))

This is actually a good idea, assuming there are no issues with lexical
scoping that might arise from --eval.  I didn't think of using
package-load-list here, but it seems that this only works if we don't
add --init-directory, because otherwise the elpa/ directory is not
populated.  It seems to me, that for a proper isolated environment, we
should add a --init-directory option.  This is easy to fix though, we
just need to specify `package-user-dir' at startup.  Here is my updated
patch, merging our approaches: