Use the default Emacs pretty-printer0.9

This is generally more robust, faster, with more attractive results.

Also gracefully handle the user quitting during
pretty-printing (common for large lists like load-history).

2 files changed, 12 insertions, 6 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2b76a24..0190e25 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,6 +19,9 @@ being linkified.
 Fixed an issue where the definition of interactively defined functions
 wasn't shown.
 
+Pretty-printing is now much more robust, gracefully handling very
+large lists.
+
 # v0.8
 
 Added setting `helpful-switch-buffer-function` to allow users to
diff --git a/helpful.el b/helpful.el
index ba10567..a2617cd 100644
--- a/helpful.el
+++ b/helpful.el
@@ -152,12 +152,15 @@ To disable cleanup entirely, set this variable to nil. See also
 
 (defun helpful--pretty-print (value)
   "Pretty-print VALUE.
-Break lists over large lines, and ensure strings are surrounded
-with double-quotes."
-  (with-temp-buffer
-    (delay-mode-hooks (lisp-mode))
-    (cl-prettyprint value)
-    (s-trim (buffer-string))))
+
+If VALUE is self-referential, or just very big, the user may
+press \\[keyboard-quit] to gracefully stop the printing."
+  ;; Inspired by `ielm-eval-input'.
+  (condition-case nil
+      (s-trim-right (pp-to-string value))
+    (quit
+     (propertize "(User quit during pretty-printing.)"
+                 'face 'font-lock-comment-face))))
 
 (defun helpful--button (text type &rest properties)
   ;; `make-text-button' mutates our string to add properties. Copy