Fix minimal allowed range for integers

Since '0' is in the positive half, negative range is slightly wider:
abs(min_value) == (max_value + 1)

Author: vitaly-burovoy

asyncpg/protocol/codecs/int.pyx

@@ -20,7 +20,7 @@ cdef bool_decode(ConnectionSettings settings, FastReadBuffer buf):
 
 cdef int2_encode(ConnectionSettings settings, WriteBuffer buf, obj):
     cdef long val = cpython.PyLong_AsLong(obj)
-    if val < -32767 or val > 32767:
+    if val < -32768 or val > 32767:
         raise ValueError(
             'integer too large to be encoded as INT2: {!r}'.format(val))
 

tests/test_codecs.py

@@ -37,15 +37,15 @@ def _timezone(offset):
         True, False,
     )),
     ('smallint', 'int2', (
-        -2 ** 15 + 1, 2 ** 15 - 1,
+        -2 ** 15, 2 ** 15 - 1,
         -1, 0, 1,
     )),
     ('int', 'int4', (
-        -2 ** 31 + 1, 2 ** 31 - 1,
+        -2 ** 31, 2 ** 31 - 1,
         -1, 0, 1,
     )),
     ('bigint', 'int8', (
-        -2 ** 63 + 1, 2 ** 63 - 1,
+        -2 ** 63, 2 ** 63 - 1,
         -1, 0, 1,
     )),
     ('numeric', 'numeric', (
@@ -474,7 +474,7 @@ async def test_invalid_input(self):
             ]),
             ('smallint', ValueError, 'integer too large', [
                 32768,
-                -32768
+                -32769
             ]),
             ('float4', ValueError, 'float value too large', [
                 4.1 * 10 ** 40,