Support functions defined in non-file buffers

2 files changed, 27 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f0fd209..57af2af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ a plain symbol.
 Fixed an issue where we would show function source code for variables
 where we can't find the variable definition.
 
+Fixed a crash on functions defined in a buffer that isn't backed by a
+file. We now provide a button to navigate to that buffer.
+
 # v0.7
 
 Helpful buffers now start with a summary of what you're looking at,
diff --git a/helpful.el b/helpful.el
index 1dce7fe..504ca8e 100644
--- a/helpful.el
+++ b/helpful.el
@@ -411,6 +411,23 @@ or disable if already enabled."
    'path path
    'position pos))
 
+(define-button-type 'helpful-buffer-button
+  'action #'helpful--switch-to-buffer
+  'buffer nil
+  'follow-link t
+  'help-echo "Switch to this buffer")
+
+(defun helpful--switch-to-buffer (button)
+  "Navigate to the buffer this BUTTON represents."
+  (switch-to-buffer (button-get button 'buffer)))
+
+(defun helpful--buffer-button (buffer)
+  "Return a button that opens PATH and puts point at POS."
+  (helpful--button
+   (buffer-name buffer)
+   'helpful-buffer-button
+   'buffer buffer))
+
 (define-button-type 'helpful-customize-button
   'action #'helpful--customize
   'symbol nil
@@ -1289,10 +1306,13 @@ OBJ may be a symbol or a compiled function object."
             (cond
              (buf
               (let ((path (buffer-file-name buf)))
-                (format
-                 "defined in %s"
-                 (helpful--navigate-button
-                  (file-name-nondirectory path) path pos))))
+                (if path
+                    (format
+                     "defined in %s"
+                     (helpful--navigate-button
+                      (file-name-nondirectory path) path pos))
+                  (format "defined in buffer %s"
+                          (helpful--buffer-button buf)))))
              (primitive-p
               "defined in C source code")
              (t