Optimise float parsing from Unicode strings with non-ASCII spaces (GH-4084)

* Reject invalid underscore placements in float parser.
* Add a proper nan/inf float parser to prevent underscore-mixes like "in_f" from passing through.

tests/run/builtin_float.py

@@ -5,7 +5,7 @@ import cython
 import sys
 
 def fix_underscores(s):
-    if sys.version_info < (3, 6):
+    if sys.version_info < (3, 6) or getattr(sys, 'pypy_version_info', (9, 9)) < (3, 7, 4):
         # Py2 float() does not support PEP-515 underscore literals
         if isinstance(s, bytes):
             if not cython.compiled and b'_' in s:
@@ -60,6 +60,18 @@ def from_bytes(s: bytes):
     1.2413112312318938e+47
     >>> from_bytes(b"123E100")
     1.23e+102
+    >>> from_bytes(b"12__._3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12__._3...
+    >>> from_bytes(b"_12.3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ..._12.3...
+    >>> from_bytes(b"12.3_")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12.3_...
+    >>> from_bytes(b"na_n")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...na_n...
     >>> from_bytes(None)  # doctest: +ELLIPSIS
     Traceback (most recent call last):
     TypeError...
@@ -95,6 +107,18 @@ def from_bytearray(s: bytearray):
     1.2413112312318938e+47
     >>> from_bytearray(bytearray(b"123E100"))
     1.23e+102
+    >>> from_bytearray(bytearray(b"12__._3"))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12__._3...
+    >>> from_bytearray(bytearray(b"_12.3"))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ..._12.3...
+    >>> from_bytearray(bytearray(b"12.3_"))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12.3_...
+    >>> from_bytearray(bytearray(b"in_f"))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...in_f...
     >>> from_bytearray(None)  # doctest: +ELLIPSIS
     Traceback (most recent call last):
     TypeError...
@@ -118,6 +142,18 @@ def from_str(s: 'str'):
     1.2413112312318938e+47
     >>> from_str("123E100")
     1.23e+102
+    >>> from_str("12__._3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12__._3...
+    >>> from_str("_12.3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ..._12.3...
+    >>> from_str("12.3_")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12.3_...
+    >>> from_str("n_an")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...n_an...
     >>> from_str(None)  # doctest: +ELLIPSIS
     Traceback (most recent call last):
     TypeError...
@@ -155,6 +191,32 @@ def from_unicode(s: 'unicode'):
     1.23e+102
     >>> from_unicode(u"123.23\\N{PUNCTUATION SPACE}")
     123.23
+    >>> from_unicode(u"\\N{PUNCTUATION SPACE} 123.23 \\N{PUNCTUATION SPACE}")
+    123.23
+    >>> from_unicode(fix_underscores(u"\\N{PUNCTUATION SPACE} 12_3.2_3 \\N{PUNCTUATION SPACE}"))
+    123.23
+    >>> from_unicode(u"\\N{PUNCTUATION SPACE} " * 25 + u"123.54 " + u"\\N{PUNCTUATION SPACE} " * 22)  # >= 40 chars
+    123.54
+    >>> from_unicode(fix_underscores(u"\\N{PUNCTUATION SPACE} " * 25 + u"1_23.5_4 " + u"\\N{PUNCTUATION SPACE} " * 22))
+    123.54
+    >>> from_unicode(u"\\N{PUNCTUATION SPACE} " + u"123.54 " * 2 + u"\\N{PUNCTUATION SPACE}")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...123.54 123.54...
+    >>> from_unicode(u"\\N{PUNCTUATION SPACE} " * 25 + u"123.54 " * 2 + u"\\N{PUNCTUATION SPACE} " * 22)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...123.54 123.54...
+    >>> from_unicode(u"_12__._3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ..._12__._3...
+    >>> from_unicode(u"_12.3")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ..._12.3...
+    >>> from_unicode(u"12.3_")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...12.3_...
+    >>> from_unicode(u"i_nf")  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ValueError: ...i_nf...
     >>> from_unicode(None)  # doctest: +ELLIPSIS
     Traceback (most recent call last):
     TypeError...