Re: Compile Mode and "host" Emacs

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 29 Oct 2013 20:09:04 +0100
> From: Sebastian Wiesner <lunaryorn@gmail.com>
> Cc: schwab@suse.de, nbtrap@nbtrap.com, emacs-devel@gnu.org
> 
> 2013/10/29 Eli Zaretskii <eliz@gnu.org>:
> >> Date: Tue, 29 Oct 2013 16:52:42 +0100
> >> From: Sebastian Wiesner <lunaryorn@gmail.com>
> >> Cc: Nathan Trapuzzano <nbtrap@nbtrap.com>, emacs-devel@gnu.org
> >>
> >> I would have preferred to have my question answered and my problem
> >> solved rather than seeing my question arrogantly dismissed as "not
> >> useful", and being lectured upon what my problem actually is.
> >
> > Perhaps if you explained in more details what is your problem, the
> > issue would become more clear, and you could get more focused replies.
> > As things stand, you only described in very general terms what you
> > want to do, and on that level, Andreas is right: the OOB tool to
> > communicate with Emacs is emacsclient.  Providing more details might
> > clarify whether emacsclient fits the bill or not, and why, and if it
> > doesn't, what might fit the bill.
> 
> "emacsclient" runs code in a running Emacs.  I don't want a use the
> running session, but rather a fresh session, but using the same Emacs.

Ah, but you could use emacsclient to provide the absolute file name of
the running Emacs, like this:

  emacsclient --eval "(concat invocation-directory invocation-name)"

and then use the result to invoke a fresh instance of the same binary.

> An Emacs Lisp developer runs her ERT tests in a fresh Emacs session.
> She has a Makefile with a "test" target, and a bunch of different
> Emacs versions installed (e.g. Emacs 23.4, Emacs 24.2, Emacs 24.3,
> three different Emacs trunk builds), to test her package against all
> supported Emacs versions.   When developing her package, she has
> different Emacs versions running in parallel to try how different
> Emacs versions behave.   She wants "M-x compile RET make test" to use
> the Emacs version she is currently in, and she does not want to
> remember to explicitly specify the target version in each Emacs
> session with "make EMACS=emacs23.4 test".

No need to remember, there could be a specialized command to
automatically add the EMACS=whatever part.

> She also byte-compiles her libraries in a fresh Emacs session to make
> sure that they cause no warnings (e.g. assignment to free variables,
> unused lexical variables, undefined functions, whatever).  For this
> purpose, she has a "compile" target in her Makefile, and she also
> wants to compile against the very she is currently in.

Same-same.

> A Emacs Lisp has written a little script to update all her installed
> packages from the command line.  As she uses a lot of packages and
> updates only once in a while, updates take long, and she wants to
> continue working meanwhile.  Thus, she calls her update script via
> "M-x compile", watches the compile buffer for progress, and calls
> "package-initialize" once the update is done, to make her Emacs use
> the new packages.  Obviously, she wants to install packages for the
> Emacs she is currently using, and not the one, which is in "$PATH".
> She has a few systems, where these are actually different:  A Fedora
> system at work, where she has no root privileges.  She installed Emacs
> trunk from source, and added it to the Gnome 3 menu.  Also an OS X
> system at home, where she installed Emacs 24.3 as App Bundle, by just
> dragging it into the "/Applications" folder.  In both cases, the
> "emacs" in $PATH is different from the Emacs she uses and starts from
> the GUI.  She does not want this Emacs to be used in her script,
> because it would break in both cases, because the system "emacs" is
> outdated.
> 
> I hope these use cases make my intend a little more clear.

They are all the same use case, and I can see at least 2 solutions,
outlined above.  One that uses custom commands which wrap "M-x compile",
the other that uses emacsclient to glean the file name of the running
binary.