Re: Can't email multipart/alternative anymore

[Aaron Ecay <aaronecay@gmail.com>]

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Hi Peter,

2015ko urriak 23an, Peter Davis-ek idatzi zuen:
> 
> Nick Dokos <ndokos@gmail.com> writes:
> 
>> Maybe set debug-on-error and try again - send the backtrace if
>> you get one. Or maybe try with -q, load a minimal .emacs with
>> org and org-mime and try that.
> 
> Here's the output from toggling debug-on-error:

Based on the backtrace, I think that if you do M-x load-library RET
ox-org RET your error should disappear.

If that’s the cause, the attached (draft) patch should give a better
error message in cases like this.

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From 4c1b170e181982fb453b87921b39ace474482040 Mon Sep 17 00:00:00 2001
From: Aaron Ecay <aaronecay@gmail.com>
Date: Fri, 23 Oct 2015 13:48:31 +0100
Subject: [PATCH] Improve invalid export backend error messages.

* lisp/ox.el (org-export-get-backend): Add `strict' argument.
(org-export-derived-backend-p, org-export-get-all-transcoders):
(org-export-get-all-filters, org-export-data-with-backend):
(org-export-as, org-export-insert-default-template):
(org-export-with-backend): Use it.
(org-export-barf-if-invalid-backend): Remove function.
---
 lisp/ox.el | 90 +++++++++++++++++++++++++++++---------------------------------
 1 file changed, 42 insertions(+), 48 deletions(-)

diff --git a/lisp/ox.el b/lisp/ox.el
index 80cbc37..d68cc3c 100644
--- a/lisp/ox.el
+++ b/lisp/ox.el
@@ -947,13 +947,18 @@ mode."
 				  (:copier nil))
   name parent transcoders options filters blocks menu)
 
-(defun org-export-get-backend (name)
+(defun org-export-get-backend (name &optional strict)
   "Return export back-end named after NAME.
-NAME is a symbol.  Return nil if no such back-end is found."
+
+NAME is a symbol.  Return nil if no such back-end is found, or
+signal an error if STRICT is non-nil."
   (catch 'found
     (dolist (b org-export-registered-backends)
       (when (eq (org-export-backend-name b) name)
-	(throw 'found b)))))
+	(throw 'found b)))
+    (when strict
+      (error "Could not locate export backend %s; try loading the library `ox-%s'"
+	     name name))))
 
 (defun org-export-register-backend (backend)
   "Register BACKEND as a known export back-end.
@@ -976,25 +981,19 @@ BACKEND is a structure with `org-export-backend' type."
     (if old (setcar (memq old org-export-registered-backends) backend)
       (push backend org-export-registered-backends))))
 
-(defun org-export-barf-if-invalid-backend (backend)
-  "Signal an error if BACKEND isn't defined."
-  (unless (org-export-backend-p backend)
-    (error "Unknown \"%s\" back-end: Aborting export" backend)))
-
 (defun org-export-derived-backend-p (backend &rest backends)
   "Non-nil if BACKEND is derived from one of BACKENDS.
 BACKEND is an export back-end, as returned by, e.g.,
 `org-export-create-backend', or a symbol referring to
 a registered back-end.  BACKENDS is constituted of symbols."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (when backend
-    (catch 'exit
-      (while (org-export-backend-parent backend)
-	(when (memq (org-export-backend-name backend) backends)
-	  (throw 'exit t))
-	(setq backend
-	      (org-export-get-backend (org-export-backend-parent backend))))
-      (memq (org-export-backend-name backend) backends))))
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
+  (catch 'exit
+    (while (org-export-backend-parent backend)
+      (when (memq (org-export-backend-name backend) backends)
+	(throw 'exit t))
+      (setq backend
+	    (org-export-get-backend (org-export-backend-parent backend))))
+    (memq (org-export-backend-name backend) backends)))
 
 (defun org-export-get-all-transcoders (backend)
   "Return full translation table for BACKEND.
@@ -1007,15 +1006,14 @@ transcoders.
 Unlike to `org-export-backend-transcoders', this function
 also returns transcoders inherited from parent back-ends,
 if any."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (when backend
-    (let ((transcoders (org-export-backend-transcoders backend))
-	  parent)
-      (while (setq parent (org-export-backend-parent backend))
-	(setq backend (org-export-get-backend parent))
-	(setq transcoders
-	      (append transcoders (org-export-backend-transcoders backend))))
-      transcoders)))
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
+  (let ((transcoders (org-export-backend-transcoders backend))
+	parent)
+    (while (setq parent (org-export-backend-parent backend))
+      (setq backend (org-export-get-backend parent))
+      (setq transcoders
+	    (append transcoders (org-export-backend-transcoders backend))))
+    transcoders))
 
 (defun org-export-get-all-options (backend)
   "Return export options for BACKEND.
@@ -1026,14 +1024,13 @@ for the shape of the return value.
 
 Unlike to `org-export-backend-options', this function also
 returns options inherited from parent back-ends, if any."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (when backend
-    (let ((options (org-export-backend-options backend))
-	  parent)
-      (while (setq parent (org-export-backend-parent backend))
-	(setq backend (org-export-get-backend parent))
-	(setq options (append options (org-export-backend-options backend))))
-      options)))
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
+  (let ((options (org-export-backend-options backend))
+	parent)
+    (while (setq parent (org-export-backend-parent backend))
+      (setq backend (org-export-get-backend parent))
+      (setq options (append options (org-export-backend-options backend))))
+    options))
 
 (defun org-export-get-all-filters (backend)
   "Return complete list of filters for BACKEND.
@@ -1044,14 +1041,13 @@ keys are symbols and values lists of functions.
 
 Unlike to `org-export-backend-filters', this function also
 returns filters inherited from parent back-ends, if any."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (when backend
-    (let ((filters (org-export-backend-filters backend))
-	  parent)
-      (while (setq parent (org-export-backend-parent backend))
-	(setq backend (org-export-get-backend parent))
-	(setq filters (append filters (org-export-backend-filters backend))))
-      filters)))
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
+  (let ((filters (org-export-backend-filters backend))
+	parent)
+    (while (setq parent (org-export-backend-parent backend))
+      (setq backend (org-export-get-backend parent))
+      (setq filters (append filters (org-export-backend-filters backend))))
+    filters))
 
 (defun org-export-define-backend (backend transcoders &rest body)
   "Define a new back-end BACKEND.
@@ -1983,7 +1979,7 @@ channel.
 
 Unlike to `org-export-with-backend', this function will
 recursively convert DATA using BACKEND translation table."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
   (org-export-data
    data
    ;; Set-up a new communication channel with translations defined in
@@ -2930,8 +2926,7 @@ with external parameters overriding Org default settings, but
 still inferior to file-local settings.
 
 Return code as a string."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (org-export-barf-if-invalid-backend backend)
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
   (save-excursion
     (save-restriction
       ;; Narrow buffer to an appropriate region or subtree for
@@ -3130,7 +3125,7 @@ locally for the subtree through node properties."
 			 ((org-export-backend-p backend)
 			  (org-export-backend-options backend))
 			 (t (org-export-backend-options
-			     (org-export-get-backend backend)))))
+			     (org-export-get-backend backend t)))))
       (let ((keyword (nth 1 entry))
             (option (nth 2 entry)))
         (cond
@@ -3620,8 +3615,7 @@ a registered back-end.  DATA is an Org element, object, secondary
 string or string.  CONTENTS, when non-nil, is the transcoded
 contents of DATA element, as a string.  INFO, when non-nil, is
 the communication channel used for export, as a plist."
-  (when (symbolp backend) (setq backend (org-export-get-backend backend)))
-  (org-export-barf-if-invalid-backend backend)
+  (when (symbolp backend) (setq backend (org-export-get-backend backend t)))
   (let ((type (org-element-type data)))
     (if (memq type '(nil org-data)) (error "No foreign transcoder available")
       (let* ((all-transcoders (org-export-get-all-transcoders backend))
-- 
2.6.1


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-- 
Aaron Ecay