Make *compilation* per-project

[sellout]

Right now any compilation/test/etc. happens in the single *compilation* buffer, so switching between projects isn't as independent as I would like (if the first project has a long compilation, I can't go work on something else and compile it while I wait for the first project to finish).

Expected behavior

• C-c p c to compile the current project
• C-c p p to switch projects
• C-c p c to compile the second project, both now compiling concurrently, ideally in buffers named something like *compilation*<project1> and *compilation*<project2>

Actual behavior

The second C-c p c says "A compilation process is running` kill it?"

Steps to reproduce the problem

The expected behavior steps should do it, I think. You need two projects that have a compilation time of over a few seconds. Using yes as the compilation command should get it to just run indefinitely.

Environment & Version information

Projectile version information

Projectile 20191216.2105

Emacs version

GNU Emacs 26.3 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.13)

Operating system

NixOS 20.03

[bbatsov]

Nice idea! I think that'd be pretty easy to implement.

[sellout]

I started poking at this, but ran into some problems.

;; Run the compilation for each project in a buffer that contains the project name.
;;
;; This works, but I use direnv, and for some reason all the *compilation*
;; buffers seem to share a common direnv environment. I.e., whenever I switch
;; between *compilation* buffers, I have to `M-x direnv-update-environment`
;; before I can compile in it.
(setq compilation-buffer-name-function
      (lambda (compilation-mode)
	(concat "*" (downcase compilation-mode) "*<" (projectile-project-name) ">")))

;; When compiling, only ask to save buffers for the project getting compiled.
;;
;; This doesn't work at all. The problem is that this gets called like
;;
;;     (with-current-buffer <unsaved-file-buffer>
;;       (funcall compilation-save-buffers-predicate))
;;
;; which means that this always returns `t`, since `(projectile-project-root)`
;; is relative to `(current-buffer)`. To complain about Emacs a bit I wish
;; `(current-buffer)` referred to the *compilation* buffer, and the
;; unsaved-file-buffer was passed as a parameter ... this is a thunk for no good
;; reason, AFAICT.
;;
;; Since the *compilation* buffers are now named based on the project, I don't
;; see how I can find the correct projectile-project-root. E.g.,
;;
;;     (let ((root (with-current-buffer "*compilation*" (projectile-project-root)))) ...)
;;
;; could approximate it if I wasn't trying to distinguish the buffers.
(setq compilation-save-buffers-predicate
      (lambda ()
	(let ((root (projectile-project-root)))
	  (or (not root)
	      (projectile-project-buffer-p (current-buffer) root)))))

[sellout]

I think the direnv thing is probably independent (wbolster/emacs-direnv#16). Just probably hadn't noticed before because I wasn't switching between projects as often.

[sellout]

For the second problem, figured out that I can do

(with-current-buffer (window-buffer) (projectile-project-root))

so that problem is solved.