Hi Shea, did you look at direnv[1] yet? I have a feeling that it would mix with emacs pretty well and implement all that you need in a more generic way (which is a pro and con).
Essentially what I do in my projects is use the following .envrc: ```bash use nix ``` The `use nix` directive calls nix-shell under the hood so then the usual default.nix and shell.nix are loaded. In emacs the plugin would need to call `direnv export json` on enter/leave of a context. This gives you a diff of environment variables to apply. There is a bit more complexity when implementing the security framework but that's about it. I'm just curious if you thought of that approach, keep up the good work! Cheers, z [1]: http://direnv.net/ On Mon, 5 Sep 2016 at 17:11 Shea Levy <[email protected]> wrote: > Sure! In my .emacs, I have: > > > (defun nix-buffer-find-file-hook () > > (when (not (file-remote-p (buffer-file-name))) > > (nix-buffer))) > > (add-hook 'find-file-hook 'nix-buffer-find-file-hook) > > I have coq 8.5pl1 installed in my configuration.nix, but I have a coq > project that requires 8.4pl6, so I have in that project's root directory > dir-locals.nix: > > > let pkgs = import <nixpkgs> {}; in > > pkgs.nixBufferBuilders.withPackages [ pkgs.coq ] > > (note that this relies on a recent nixpkgs commit[1]). Then whenever I > open a .v file in the project, ProofGeneral uses coq 8.4 rather than > 8.5. > > If I wanted, my dir-locals.nix could take a 'root' argument, which would > point to the file I opened. > > ~Shea > > [1]: > https://github.com/NixOS/nixpkgs/commit/05c132486d8cfae600bbfe8c9ac5d799b298afed > > Bas van Dijk <[email protected]> writes: > > > Hi Shea, > > > > As a Nix and Emacs user this looks very interesting. I didn't know about > > Buffer-Local Variables before. > > > > Can you share some applications of nix-buffer / how you are using it? > > > > Thanks! > > > > Bas > > > > On 5 September 2016 at 08:06, Shea Levy <[email protected]> wrote: > > > >> Hi all, > >> > >> I've just pushed the initial version of nix-buffer[1], and opened a PR > >> for adding it to melpa[2]. The description of the 'nix-buffer-enter' > >> command this library defines: > >> > >> > Set up the buffer according to the directory-local nix expression. > >> > > >> > Looks for dir-locals.nix upward from the current directory. If found, > >> > builds the derivation defined there with the 'root' arg set to the > >> > current buffer file name or directory and evaluates the resulting > >> > elisp if safe to do so. > >> > > >> > Because in practice dir-locals.nix will always want to do things that > >> > are unsafe in dir-locals.el (e.g. append to 'exec-path'), we don't > >> > reuse that mechanism and instead just load the file as elisp. Because > >> > this allows arbitrary code execution, the first time we're asked to > >> > load a particular store path we query the user to verify if it's safe > >> > to load beforehand. > >> > > >> > The Lisp code generated by dir-locals.nix should limit itself to > >> > modifying buffer-local variables, but there is no actual enforcement > >> > of this. 'setq-local' is your friend. > >> > >> It may be useful to advise the 'normal-mode' function to call > >> 'nix-buffer-enter' beforehand for local files, so that all visited files > >> have their environments set up before modes are loaded. > >> > >> Note that this is my first elisp package, so feedback definitely > >> welcome! > >> > >> In addition to the elisp work mentioned in the TODO[3], it would be > >> useful to add some functions to nixpkgs to build elisp files, > >> especially: > >> > >> * A function taking a derivation and building an elisp file that sets up > >> the buffer environment analogous to the build environment specified by > >> that derivation > >> * A function taking a list of packages and building an elisp file that > >> sets up the buffer environment with all of those packages available > >> (in PATH, in the emacs load path, etc.). > >> > >> Happy hacking! > >> > >> ~Shea > >> > >> [1]: https://github.com/shlevy/nix-buffer/tree/v1.0 > >> [2]: https://github.com/melpa/melpa/pull/4204 > >> [3]: https://github.com/shlevy/nix-buffer/blob/v1.0/TODO.md > >> > >> _______________________________________________ > >> nix-dev mailing list > >> [email protected] > >> http://lists.science.uu.nl/mailman/listinfo/nix-dev > >> > >> > _______________________________________________ > nix-dev mailing list > [email protected] > http://lists.science.uu.nl/mailman/listinfo/nix-dev >
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