fix: correctly strip/restore initial punctuation (#3336)

* refactor(punctuation): remove orphan code for handling lone punctuation

The case of lone punctuation is already handled at the top of restore(). The
removed if statement would never be called and would in fact raise an
AttributeError because the _punc_index named tuple doesn't have the attribute
`mark`.

* refactor(punctuation): remove unused argument

* fix(punctuation): correctly handle initial punctuation

Stripping and restoring initial punctuation didn't work correctly because the
string-splitting caused an additional empty string to be inserted in the text
list (because `".A".split(".")` => `["", "A"]`). Now, an initial empty string is
skipped and relevant test cases are added.

Fixes #3333

TTS/tts/utils/text/punctuation.py

@@ -15,7 +15,6 @@ class PuncPosition(Enum):
     BEGIN = 0
     END = 1
     MIDDLE = 2
-    ALONE = 3
 
 
 class Punctuation:
@@ -92,7 +91,7 @@ class Punctuation:
             return [text], []
         # the text is only punctuations
         if len(matches) == 1 and matches[0].group() == text:
-            return [], [_PUNC_IDX(text, PuncPosition.ALONE)]
+            return [], [_PUNC_IDX(text, PuncPosition.BEGIN)]
         # build a punctuation map to be used later to restore punctuations
         puncs = []
         for match in matches:
@@ -107,11 +106,14 @@ class Punctuation:
         for idx, punc in enumerate(puncs):
             split = text.split(punc.punc)
             prefix, suffix = split[0], punc.punc.join(split[1:])
+            text = suffix
+            if prefix == "":
+                # We don't want to insert an empty string in case of initial punctuation
+                continue
             splitted_text.append(prefix)
             # if the text does not end with a punctuation, add it to the last item
             if idx == len(puncs) - 1 and len(suffix) > 0:
                 splitted_text.append(suffix)
-            text = suffix
         return splitted_text, puncs
 
     @classmethod
@@ -127,10 +129,10 @@ class Punctuation:
             ['This is', 'example'], ['.', '!'] -> "This is. example!"
 
         """
-        return cls._restore(text, puncs, 0)
+        return cls._restore(text, puncs)
 
     @classmethod
-    def _restore(cls, text, puncs, num):  # pylint: disable=too-many-return-statements
+    def _restore(cls, text, puncs):  # pylint: disable=too-many-return-statements
         """Auxiliary method for Punctuation.restore()"""
         if not puncs:
             return text
@@ -142,21 +144,18 @@ class Punctuation:
         current = puncs[0]
 
         if current.position == PuncPosition.BEGIN:
-            return cls._restore([current.punc + text[0]] + text[1:], puncs[1:], num)
+            return cls._restore([current.punc + text[0]] + text[1:], puncs[1:])
 
         if current.position == PuncPosition.END:
-            return [text[0] + current.punc] + cls._restore(text[1:], puncs[1:], num + 1)
-
-        if current.position == PuncPosition.ALONE:
-            return [current.mark] + cls._restore(text, puncs[1:], num + 1)
+            return [text[0] + current.punc] + cls._restore(text[1:], puncs[1:])
 
         # POSITION == MIDDLE
         if len(text) == 1:  # pragma: nocover
             # a corner case where the final part of an intermediate
             # mark (I) has not been phonemized
-            return cls._restore([text[0] + current.punc], puncs[1:], num)
+            return cls._restore([text[0] + current.punc], puncs[1:])
 
-        return cls._restore([text[0] + current.punc + text[1]] + text[2:], puncs[1:], num)
+        return cls._restore([text[0] + current.punc + text[1]] + text[2:], puncs[1:])
 
 
 # if __name__ == "__main__":

tests/text_tests/test_punctuation.py

@@ -11,6 +11,11 @@ class PunctuationTest(unittest.TestCase):
             ("This, is my text ... to be striped !! from text", "This is my text to be striped from text"),
             ("This, is my text ... to be striped  from text?", "This is my text to be striped  from text"),
             ("This, is my text to be striped from text", "This is my text to be striped from text"),
+            (".", ""),
+            (" . ", ""),
+            ("!!! Attention !!!", "Attention"),
+            ("!!! Attention !!! This is just a ... test.", "Attention This is just a test"),
+            ("!!! Attention! This is just a ... test.", "Attention This is just a test"),
         ]
 
     def test_get_set_puncs(self):