From e8fa5c812caadbeb827272c1e30b1938f78589d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20Benn=C3=A9e?= <alex.bennee@linaro.org>
Date: Mon, 20 Feb 2017 17:11:52 +0000
Subject: [PATCH] async: allow passing of initfile to child process (FR#39)

Sometimes passing all your state setup in the async elisp call can be
painful, especially if the library is being used by another one (in my
case ob-async for org-mode). Luckily we have a method for dealing with
boilerplate setup called an initfile. This allows an initfile to be
specified for all async calls. It does not re-use the existing
initfile as the interactive one is likely too cluttered for a child
process.
---
 async.el | 43 ++++++++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 15 deletions(-)

diff --git a/async.el b/async.el
index 30476e2..7ce6058 100644
--- a/async.el
+++ b/async.el
@@ -44,6 +44,13 @@
 (defvar async-callback-value-set nil)
 (defvar async-current-process nil)
 (defvar async--procvar nil)
+(defvar async-child-init nil
+  "Initialisation file for async child Emacs.
+
+If defined this allows for an init file to setup the child Emacs. It
+should not be your normal init.el as that would likely load more
+things that you require. It should limit itself to ensuring paths have
+been setup so any async code can load libraries you expect.")
 
 (defun async-inject-variables
   (include-regexp &optional predicate exclude-regexp)
@@ -231,6 +238,20 @@ working directory."
         (set (make-local-variable 'async-callback-for-process) t))
       proc)))
 
+(defun async--emacs-program-args (&optional sexp)
+  "Return a list of arguments for invoking the child Emacs."
+  ;; Using `locate-library' ensure we use the right file
+  ;; when the .elc have been deleted.
+  (let ((args (list "-Q" "-l" (locate-library "async"))))
+    (when async-child-init
+      (setq args (append args (list "-l" async-child-init))))
+    (append args (list "-batch" "-f" "async-batch-invoke"
+                       (if sexp
+                           (with-temp-buffer
+                             (async--insert-sexp (list 'quote sexp))
+                             (buffer-string))
+                           "<none>")))))
+
 ;;;###autoload
 (defun async-start (start-func &optional finish-func)
   "Execute START-FUNC (often a lambda) in a subordinate Emacs process.
@@ -283,21 +304,13 @@ returns nil.  It can still be useful, however, as an argument to
 	;; Subordinate Emacs will send text encoded in UTF-8.
 	(coding-system-for-read 'utf-8-unix))
     (setq async--procvar
-          (async-start-process
-           "emacs" (file-truename
-                    (expand-file-name invocation-name
-                                      invocation-directory))
-           finish-func
-           "-Q" "-l"
-           ;; Using `locate-library' ensure we use the right file
-           ;; when the .elc have been deleted.
-           (locate-library "async")
-           "-batch" "-f" "async-batch-invoke"
-           (if async-send-over-pipe
-               "<none>"
-               (with-temp-buffer
-                 (async--insert-sexp (list 'quote sexp))
-                 (buffer-string)))))
+          (apply 'async-start-process
+                 "emacs" (file-truename
+                          (expand-file-name invocation-name
+                                            invocation-directory))
+                 finish-func
+                 (async--emacs-program-args (if (not async-send-over-pipe) sexp))))
+
     (if async-send-over-pipe
         (async--transmit-sexp async--procvar (list 'quote sexp)))
     async--procvar))