[#46] Add apheleia-goto-error

README.md

@@ -169,6 +169,11 @@ run.
 Apheleia does not currently support TRAMP, and is therefore
 automatically disabled for remote files.
 
+If an error occurs while formatting, a message is displayed in the
+echo area. You can jump to the error by invoking `M-x
+apheleia-goto-error`, or manually switch to the log buffer mentioned
+in the message.
+
 You can configure error reporting using the following user options:
 
 * `apheleia-hide-log-buffers`: By default, errors from formatters are
@@ -178,7 +183,8 @@ You can configure error reporting using the following user options:
   must type a space to see them).
 * `apheleia-log-only-errors`: By default, only failed formatter runs
   are logged. If you customize this user option to nil then all runs
-  are logged, along with whether or not they succeeded.
+  are logged, along with whether or not they succeeded. This could be
+  helpful in debugging.
 
 The following user options are also available:
 

apheleia.el

@@ -284,6 +284,10 @@ contains the patch."
 Keeping track of this helps avoid running more than one process
 at once.")
 
+(defvar apheleia--last-error-marker nil
+  "Marker for the last error message for any formatter.
+This points into a log buffer.")
+
 (cl-defun apheleia--make-process
     (&key command stdin callback ensure exit-status formatter)
   "Wrapper for `make-process' that behaves a bit more nicely.
@@ -352,6 +356,12 @@ correspond to a formatter."
                                (unless (bobp)
                                  (insert
                                   "\n\n\C-l\n"))
+                               (unless exit-ok
+                                 (unless apheleia--last-error-marker
+                                   (setq apheleia--last-error-marker
+                                         (make-marker))
+                                   (move-marker
+                                    apheleia--last-error-marker (point))))
                                (insert
                                 (current-time-string)
                                 " :: "
@@ -417,6 +427,14 @@ correspond to a formatter."
           (process-send-eof apheleia--current-process))
       (error (message "Failed to run %s: %s" name (error-message-string e))))))
 
+(defun apheleia-goto-error ()
+  "Go to the most recently reported formatter error message."
+  (interactive)
+  (unless apheleia--last-error-marker
+    (user-error "No error has happened yet"))
+  (pop-to-buffer (marker-buffer apheleia--last-error-marker))
+  (goto-char apheleia--last-error-marker))
+
 (defun apheleia--write-region-silently
     (start end filename &optional
            append visit lockname mustbenew write-region)