Add jsonian-edit-string-hook

This should allow `jsonian` users to apply arbitrary changes (such as major mode changes)
to the edit string environment.

Fixes #58

Author: iwahbe

jsonian-tests.el

@@ -832,5 +832,31 @@ If START and END are provided, they are set as point and mark."
       (should (equal b (current-buffer)))
       (should (string= (buffer-string) json-string)))))
 
+(ert-deftest jsonian-edit-string-hook ()
+  "Test `jsonian-edit-string' moves to a new buffer and then returns correctly."
+  (with-temp-buffer
+    (let* ((json-string "{\"key\": \"some complex value\\nwith new lines\"}")
+          (b (current-buffer))
+          (edit-buffer nil)
+          (hook-fn (lambda ()
+                     (should (string= "some complex value\nwith new lines" (buffer-string)))
+                     (should (not (equal (current-buffer) b)))
+                     (setq edit-buffer (current-buffer))
+                     (text-mode))))
+      (add-hook 'jsonian-edit-string-hook hook-fn)
+      (jsonian-mode)
+      (insert json-string)
+      (goto-char 10) ;; Move the point into the "complex" string
+      (jsonian-edit-string)
+      (should (eq major-mode 'text-mode))
+      (should (equal (current-buffer) edit-buffer))
+      (delete-region (point-min) (point-max))
+      (insert "some new value")
+      (jsonian-edit-mode-return)
+      (should (equal b (current-buffer)))
+      (should (string= (buffer-string) "{\"key\": \"some new value\"}"))
+      (should (eq major-mode 'jsonian-mode))
+      (remove-hook 'jsonian-edit-string-hook hook-fn))))
+
 (provide 'jsonian-tests)
 ;;; jsonian-tests.el ends here

jsonian.el

@@ -1084,6 +1084,11 @@ POS must be a valid node location."
 (defvar-local jsonian-edit-return-var nil
   "Information necessary to jump back from `jsonian--edit-mode'.")
 
+(defvar jsonian-edit-string-hook nil
+  "A normal hook run when `jsonian-edit-string' is called.
+
+It is run in the context of the edit buffer.")
+
 (defun jsonian-edit-string ()
   "Edit the string at point in another buffer."
   (interactive)
@@ -1100,6 +1105,7 @@ POS must be a valid node location."
         (insert text)
         (jsonian--unintern-special-chars (current-buffer))
         (goto-char (point-min))
+        (run-hooks 'jsonian-edit-string-hook)
         (setq-local jsonian-edit-return-var (make-jsonian--edit-return
                                              :match match
                                              :back-buffer cbuffer