lib: Audit all notmuch_database call for Xapian exception handling.

Our current approach is for top-level entry poitns in the library
to have try/catch blocks that catch any Xapian exception and print
a message. Add a few missing blocks and fix up the documentation.

lib/database.cc

@@ -341,6 +341,7 @@ notmuch_database_find_message (notmuch_database_t *notmuch,
     notmuch_private_status_t status;
     unsigned int doc_id;
 
+    try {
 	status = _notmuch_database_find_unique_doc_id (notmuch, "id",
 						       message_id, &doc_id);
 
@@ -348,6 +349,12 @@ notmuch_database_find_message (notmuch_database_t *notmuch,
 	    return NULL;
 
 	return _notmuch_message_create (notmuch, notmuch, doc_id, NULL);
+    } catch (const Xapian::Error &error) {
+	fprintf (stderr, "A Xapian exception occurred finding message: %s.\n",
+		 error.get_msg().c_str());
+	notmuch->exception_reported = TRUE;
+	return NULL;
+    }
 }
 
 /* Advance 'str' past any whitespace or RFC 822 comments. A comment is
@@ -1152,7 +1159,14 @@ notmuch_database_get_directory (notmuch_database_t *notmuch,
 {
     notmuch_status_t status;
 
+    try {
 	return _notmuch_directory_create (notmuch, path, &status);
+    } catch (const Xapian::Error &error) {
+	fprintf (stderr, "A Xapian exception occurred getting directory: %s.\n",
+		 error.get_msg().c_str());
+	notmuch->exception_reported = TRUE;
+	return NULL;
+    }
 }
 
 static const char *
@@ -1591,7 +1605,7 @@ notmuch_database_add_message (notmuch_database_t *notmuch,
 	_notmuch_message_sync (message);
     } catch (const Xapian::Error &error) {
 	fprintf (stderr, "A Xapian exception occurred adding message: %s.\n",
-		 error.get_description().c_str());
+		 error.get_msg().c_str());
 	notmuch->exception_reported = TRUE;
 	ret = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
 	goto DONE;
@@ -1616,7 +1630,7 @@ notmuch_database_remove_message (notmuch_database_t *notmuch,
 				 const char *filename)
 {
     Xapian::WritableDatabase *db;
-    void *local = talloc_new (notmuch);
+    void *local;
     const char *prefix = _find_prefix ("file-direntry");
     char *direntry, *term;
     Xapian::PostingIterator i, end;
@@ -1627,8 +1641,12 @@ notmuch_database_remove_message (notmuch_database_t *notmuch,
     if (status)
 	return status;
 
+    local = talloc_new (notmuch);
+
     db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
 
+    try {
+
 	status = _notmuch_database_filename_to_direntry (local, notmuch,
 							 filename, &direntry);
 	if (status)
@@ -1659,6 +1677,12 @@ notmuch_database_remove_message (notmuch_database_t *notmuch,
 		status = NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID;
 	    }
 	}
+    } catch (const Xapian::Error &error) {
+	fprintf (stderr, "Error: A Xapian exception occurred removing message: %s\n",
+		 error.get_msg().c_str());
+	notmuch->exception_reported = TRUE;
+	status = NOTMUCH_STATUS_XAPIAN_EXCEPTION;
+    }
 
     talloc_free (local);
 
@@ -1703,7 +1727,15 @@ notmuch_tags_t *
 notmuch_database_get_all_tags (notmuch_database_t *db)
 {
     Xapian::TermIterator i, end;
+
+    try {
 	i = db->xapian_db->allterms_begin();
 	end = db->xapian_db->allterms_end();
 	return _notmuch_convert_tags(db, i, end);
+    } catch (const Xapian::Error &error) {
+	fprintf (stderr, "A Xapian exception occurred getting tags: %s.\n",
+		 error.get_msg().c_str());
+	db->exception_reported = TRUE;
+	return NULL;
+    }
 }

lib/notmuch.h

@@ -219,6 +219,8 @@ notmuch_database_upgrade (notmuch_database_t *database,
  * Here, 'path' should be a path relative to the path of 'database'
  * (see notmuch_database_get_path), or else should be an absolute path
  * with initial components that match the path of 'database'.
+ *
+ * Can return NULL if a Xapian exception occurs.
  */
 notmuch_directory_t *
 notmuch_database_get_directory (notmuch_database_t *database,
@@ -246,6 +248,9 @@ notmuch_database_get_directory (notmuch_database_t *database,
  *
  * NOTMUCH_STATUS_SUCCESS: Message successfully added to database.
  *
+ * NOTMUCH_STATUS_XAPIAN_EXCEPTION: A Xapian exception occurred,
+ *	message not added.
+ *
  * NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID: Message has the same message
  *	ID as another message already in the database. The new
  *	filename was successfully added to the message in the database
@@ -280,6 +285,9 @@ notmuch_database_add_message (notmuch_database_t *database,
  * NOTMUCH_STATUS_SUCCESS: The last filename was removed and the
  *	message was removed from the database.
  *
+ * NOTMUCH_STATUS_XAPIAN_EXCEPTION: A Xapian exception occurred,
+ *	message not removed.
+ *
  * NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID: This filename was removed but
  *	the message persists in the database with at least one other
  *	filename.
@@ -297,8 +305,11 @@ notmuch_database_remove_message (notmuch_database_t *database,
  * a new notmuch_message_t object is returned. The caller should call
  * notmuch_message_destroy when done with the message.
  *
- * If no message is found with the given message_id or if an
+ * This function returns NULL in the following situations:
- * out-of-memory situation occurs, this function returns NULL.
+ *
+ *	* No message is found with the given message_id
+ *	* An out-of-memory situation occurs
+ *	* A Xapian exception occurs
  */
 notmuch_message_t *
 notmuch_database_find_message (notmuch_database_t *database,