Improve numeric pprinting

Author: Zac-HD

hypothesis-python/RELEASE.rst

@@ -0,0 +1,12 @@
+RELEASE_TYPE: patch
+
+This patch improves our pretty-printer for unusual numbers.
+
+- Signalling NaNs are now represented by using the :mod:`struct` module
+  to show the exact value by converting from a hexadecimal integer
+
+- CPython `limits integer-to-string conversions
+  <https://docs.python.org/3/library/stdtypes.html#integer-string-conversion-length-limitation>`__
+  to mitigate DDOS attacks.  We now use hexadecimal for very large
+  integers, and include underscore separators for integers with ten
+  or more digits.

hypothesis-python/src/hypothesis/vendor/pretty.py

@@ -143,8 +143,6 @@ def __init__(self, output=None, *, context=None):
         self.group_queue = GroupQueue(root_group)
         self.indentation = 0
 
-        self.snans = 0
-
         self.stack = []
         self.singleton_pprinters = {}
         self.type_pprinters = {}
@@ -358,12 +356,6 @@ def _enumerate(self, seq):
 
     def flush(self):
         """Flush data that is left in the buffer."""
-        if self.snans:
-            # Reset self.snans *before* calling breakable(), which might flush()
-            snans = self.snans
-            self.snans = 0
-            self.breakable("  ")
-            self.text(f"# Saw {snans} signaling NaN" + "s" * (snans > 1))
         for data in self.buffer:
             self.output_width += data.output(self.output, self.output_width)
         self.buffer.clear()
@@ -747,19 +739,31 @@ def _exception_pprint(obj, p, cycle):
             p.pretty(arg)
 
 
+def _repr_integer(obj, p, cycle):
+    if abs(obj) < 1_000_000_000:
+        p.text(repr(obj))
+    elif abs(obj) < 10**640:
+        # add underscores for integers over ten decimal digits
+        p.text(f"{obj:#_d}")
+    else:
+        # for very very large integers, use hex because power-of-two bases are cheaper
+        # https://docs.python.org/3/library/stdtypes.html#integer-string-conversion-length-limitation
+        p.text(f"{obj:#_x}")
+
+
 def _repr_float_counting_nans(obj, p, cycle):
-    if isnan(obj) and hasattr(p, "snans"):
+    if isnan(obj):
         if struct.pack("!d", abs(obj)) != struct.pack("!d", float("nan")):
-            p.snans += 1
-        if copysign(1.0, obj) == -1.0:
-            p.text("-nan")
-            return
+            show = hex(*struct.unpack("Q", struct.pack("d", obj)))
+            return p.text(f"struct.unpack('d', struct.pack('Q', {show}))[0]")
+        elif copysign(1.0, obj) == -1.0:
+            return p.text("-nan")
     p.text(repr(obj))
 
 
 #: printers for builtin types
 _type_pprinters = {
-    int: _repr_pprint,
+    int: _repr_integer,
     float: _repr_float_counting_nans,
     str: _repr_pprint,
     tuple: _seq_pprinter_factory("(", ")", tuple),

hypothesis-python/tests/cover/test_pretty.py

@@ -48,6 +48,7 @@
 """
 
 import re
+import struct
 import warnings
 from collections import Counter, OrderedDict, defaultdict, deque
 from enum import Enum, Flag
@@ -58,6 +59,7 @@
 from hypothesis import given, strategies as st
 from hypothesis.control import current_build_context
 from hypothesis.internal.compat import PYPY
+from hypothesis.internal.conjecture.floats import float_to_lex
 from hypothesis.internal.floats import SIGNALING_NAN
 from hypothesis.vendor import pretty
 
@@ -603,13 +605,15 @@ def test_breakable_at_group_boundary():
     [
         (float("nan"), "nan"),
         (-float("nan"), "-nan"),
-        (SIGNALING_NAN, "nan  # Saw 1 signaling NaN"),
-        (-SIGNALING_NAN, "-nan  # Saw 1 signaling NaN"),
-        ((SIGNALING_NAN, SIGNALING_NAN), "(nan, nan)  # Saw 2 signaling NaNs"),
+        (SIGNALING_NAN, "struct.unpack('d', struct.pack('Q', 0x7ff8000000000001))[0]"),
+        (-SIGNALING_NAN, "struct.unpack('d', struct.pack('Q', 0xfff8000000000001))[0]"),
     ],
 )
 def test_nan_reprs(obj, rep):
     assert pretty.pretty(obj) == rep
+    assert float_to_lex(obj) == float_to_lex(
+        eval(rep, {"struct": struct, "nan": float("nan")})
+    )
 
 
 def _repr_call(*args, **kwargs):
@@ -739,3 +743,18 @@ def test_pprint_map_with_cycle(data):
     p = pretty.RepresentationPrinter(context=current_build_context())
     p.pretty(x)
     assert p.getvalue() == "ValidSyntaxRepr(...)"
+
+
+def test_pprint_large_integers():
+    p = pretty.RepresentationPrinter()
+    p.pretty(1234567890)
+    assert p.getvalue() == "1_234_567_890"
+
+
+def test_pprint_extremely_large_integers():
+    x = 10**5000  # repr fails with ddos error
+    p = pretty.RepresentationPrinter()
+    p.pretty(x)
+    got = p.getvalue()
+    assert got == f"{x:#_x}"  # hexadecimal with underscores
+    assert eval(got) == x