obj.py: InitErrors: allow selected exceptions to be passed through

mmgen/obj.py

@@ -133,7 +133,9 @@ class InitErrors:
 		if m2:
 			errmsg = repr(m2) + '\n' + errmsg
 
-		if hasattr(cls,'exc'):
+		if hasattr(cls,'passthru_excs') and type(e) in cls.passthru_excs:
+			raise
+		elif hasattr(cls,'exc'):
 			raise cls.exc(errmsg)
 		else:
 			raise ObjectInitError(errmsg)
@@ -684,6 +686,7 @@ class TwMMGenID(str,Hilite,InitErrors,MMGenObject):
 # non-displaying container for TwMMGenID,TwComment
 class TwLabel(str,InitErrors,MMGenObject):
 	exc = BadTwLabel
+	passthru_excs = (BadTwComment,)
 	def __new__(cls,proto,text):
 		if type(text) == cls:
 			return text

mmgen/tw.py

@@ -33,8 +33,7 @@ def CUR_RIGHT(n): return '\033[{}C'.format(n)
 
 def get_tw_label(proto,s):
 	"""
-	We must fail only on malformed comment, not on empty label.
-	Otherwise, listaddresses showempty=1 will fail.
+	raise an exception on a malformed comment, return None on an empty or invalid label
 	"""
 	try:
 		return TwLabel(proto,s)

test/objtest.py

@@ -72,6 +72,10 @@ def run_test(test,arg,input_data,arg1,exc_name):
 			ret_chk = arg['ret']
 			del arg['ret']
 			del arg_copy['ret']
+		if 'exc_name' in arg:
+			exc_name = arg['exc_name']
+			del arg['exc_name']
+			del arg_copy['exc_name']
 		if 'ret_idx' in arg:
 			ret_idx = arg['ret_idx']
 			del arg['ret_idx']

test/objtest_py_d/ot_btc_mainnet.py

@@ -181,7 +181,7 @@ tests = {
 			{'text':tw_pfx+' x',     'proto':proto},
 			{'text':tw_pfx+'я x',    'proto':proto},
 			{'text':utf8_ctrl[:40],  'proto':proto},
-			{'text':'F00BAA12:S:1 '+ utf8_ctrl[:40], 'proto':proto, },
+			{'text':'F00BAA12:S:1 ' + utf8_ctrl[:40], 'proto':proto, 'exc_name': 'BadTwComment'},
 		),
 		'good':  (
 			{'text':'F00BAA12:99 a comment',            'proto':proto, 'ret':'F00BAA12:L:99 a comment'},