Fix regex to deal with mixing of quotes at start of string

pydocstringformatter/_formatting/base.py

@@ -73,7 +73,7 @@ def treat_token(self, tokeninfo: tokenize.TokenInfo) -> tokenize.TokenInfo:
 class StringAndQuotesFormatter(Formatter):
     """Base class for string formatter that needs access to the quotes."""
 
-    quotes_regex = re.compile(r"""['"]{1,3}""")
+    quotes_regex = re.compile(r"""^('{3}|'|"{3}|")""")
     """Pattern to match against opening quotes."""
 
     @abc.abstractmethod

tests/data/format/quotes_type/mix_with_double_at_start.py

@@ -0,0 +1,11 @@
+def a(self):
+    "'a.m.' or 'p.m.'"
+
+def b(self):
+    """'a.m.' or 'p.m.'"""
+
+def c(self):
+    "'''a.m.''' or 'p.m.'"
+
+def d(self):
+    """'''a.m.''' or 'p.m.'"""

tests/data/format/quotes_type/mix_with_double_at_start.py.out

@@ -0,0 +1,11 @@
+def a(self):
+    """'A.m.' or 'p.m.'."""
+
+def b(self):
+    """'a.m.' or 'p.m.'."""
+
+def c(self):
+    """'''a.m.''' or 'p.m.'."""
+
+def d(self):
+    """'''a.m.''' or 'p.m.'."""

tests/data/format/quotes_type/mix_with_single_at_start.py

@@ -0,0 +1,11 @@
+def a(self):
+    '"a.m." or "p.m."'
+
+def b(self):
+    '''"a.m." or "p.m."'''
+
+def c(self):
+    '"""a.m.""" or "p.m."'
+
+def d(self):
+    '''"""a.m.""" or "p.m."'''

tests/data/format/quotes_type/mix_with_single_at_start.py.out

@@ -0,0 +1,11 @@
+def a(self):
+    """"A.m." or "p.m."."""
+
+def b(self):
+    """"a.m." or "p.m."."""
+
+def c(self):
+    """"""a.m.""" or "p.m."."""
+
+def d(self):
+    """"""a.m.""" or "p.m."."""