helpful

commit 866d5daecb168c0b62c91ccf5dec833d5cdcac5c
parent ddd1f2c6794972e16393614716532fc1753edd31
Author: Wilfred Hughes <me@wilfred.me.uk>
Date:   Thu, 11 Jul 2019 00:56:22 +0100

Show the original value for defcustom variables

Fixes #199

Diffstat:
M
CHANGELOG.md
 | 
2
++
M
helpful.el
 | 
26
++++++++++++++++++++++++++
M
test/helpful-unit-test.el
 | 
14
++++++++++++++

3 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,7 @@
 # v0.18 (unreleased)
 
+Show the original value for custom variables whose value has changed.
+
 # v0.17
 
 Fixed a minor docstring formatting issue when keymap references were
diff --git a/helpful.el b/helpful.el
@@ -2021,6 +2021,25 @@ may contain duplicates."
    (t
     (helpful--pretty-print value))))
 
+(defun helpful--original-value (sym)
+  "Return the original value for SYM, if any.
+
+If SYM has an original value, return it in a list. Return nil
+otherwise."
+  (let* ((orig-val-expr (get sym 'standard-value)))
+    (when (consp orig-val-expr)
+      (ignore-errors
+        (list
+         (eval (car orig-val-expr)))))))
+
+(defun helpful--original-value-differs-p (sym)
+  "Return t if SYM has an original value, and its current
+value is different."
+  (let ((orig-val-list (helpful--original-value sym)))
+    (and (consp orig-val-list)
+         (not (eq (car orig-val-list)
+                  (symbol-value sym))))))
+
 (defun helpful-update ()
   "Update the current *Helpful* buffer to the latest
 state of the current symbol."
@@ -2105,6 +2124,13 @@ state of the current symbol."
            (t "Value")))
          (helpful--format-value sym val)
          "\n\n")
+        (when (helpful--original-value-differs-p sym)
+          (insert
+           (helpful--heading "Original Value")
+           (helpful--format-value
+            sym
+            (car (helpful--original-value sym)))
+           "\n\n"))
         (when multiple-views-p
           (insert (helpful--make-toggle-literal-button) " "))
 
diff --git a/test/helpful-unit-test.el b/test/helpful-unit-test.el
@@ -950,3 +950,17 @@ find the source code."
   ;; loaded.
   ;;
   (helpful-function #'tetris))
+
+(defcustom helpful-test-custom-var 123
+  "I am an example custom variable."
+  :type 'number
+  :group 'helpful)
+
+;; Ensure the current value differs from the original value.
+(setq helpful-test-custom-var 456)
+
+(ert-deftest helpful--original-value ()
+  "Show the original value for defcustom variables."
+  (helpful-variable 'helpful-test-custom-var)
+  (should
+   (s-contains-p "Original Value\n123" (buffer-string))))