helpful

commit afb2ccc0d71f233918b1ccd027af5023637654f4
parent c70db01c19dfc88a7781eb841bcace148617814f
Author: Wilfred Hughes <me@wilfred.me.uk>
Date:   Sun, 14 Feb 2021 19:26:57 -0800

Merge pull request #257 from iwahbe/fix-circular-structure-pprint

Fix helpful--pretty-print on circular structures
Diffstat:
M
CHANGELOG.md
 | 
2
++
M
helpful.el
 | 
10
+++++++---

2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -3,6 +3,8 @@
 Fixed a hang when looking at functions that had advice but hadn't yet
 been loaded by the autoloader (#179, #191).
 
+Fixed issue with displaying circular data structures.
+
 # v0.18
 
 Show the original value for custom variables whose value has changed.
diff --git a/helpful.el b/helpful.el
@@ -181,11 +181,15 @@ can make Helpful very slow.")
 (defun helpful--pretty-print (value)
   "Pretty-print VALUE.
 
-If VALUE is self-referential, or just very big, the user may
-press \\[keyboard-quit] to gracefully stop the printing."
+If VALUE is very big, the user may press \\[keyboard-quit] to
+gracefully stop the printing. If VALUE is self-referential, the
+error will be caught and displayed."
   ;; Inspired by `ielm-eval-input'.
-  (condition-case nil
+  (condition-case err
       (s-trim-right (pp-to-string value))
+    (error
+     (propertize (format "(Display error: %s)" (cadr err))
+                 'face 'font-lock-comment-face))
     (quit
      (propertize "(User quit during pretty-printing.)"
                  'face 'font-lock-comment-face))))