Prohibit non-iterable containers to be passed as array input

Make the array input type check for correct ABCs instead of producing a
cryptic error when a non-iterable container is passed.

Author: elprans

asyncpg/__init__.py

@@ -15,4 +15,4 @@
 __all__ = ('connect', 'create_pool', 'Record', 'Connection') + \
           exceptions.__all__  # NOQA
 
-__version__ = '0.15.0'
+__version__ = '0.16.0.dev0'

asyncpg/protocol/codecs/array.pyx

@@ -5,7 +5,7 @@
 # the Apache 2.0 License: http://www.apache.org/licenses/LICENSE-2.0
 
 
-from collections.abc import Container as ContainerABC
+from collections.abc import Iterable as IterableABC, Sized as SizedABC
 
 
 DEF ARRAY_MAXDIM = 6  # defined in postgresql/src/includes/c.h
@@ -30,13 +30,18 @@ cdef inline bint _is_trivial_container(object obj):
             PyByteArray_Check(obj) or PyMemoryView_Check(obj)
 
 
-cdef inline _is_container(object obj):
-    return not _is_trivial_container(obj) and isinstance(obj, ContainerABC)
+cdef inline _is_array_iterable(object obj):
+    return (
+        isinstance(obj, IterableABC) and
+        isinstance(obj, SizedABC) and
+        not _is_trivial_container(obj)
+    )
 
 
-cdef inline _is_sub_array(object obj):
-    return not _is_trivial_container(obj) and isinstance(obj, ContainerABC) \
-            and not cpython.PyTuple_Check(obj)
+cdef inline _is_sub_array_iterable(object obj):
+    # Sub-arrays have a specialized check, because we treat
+    # nested tuples as records.
+    return _is_array_iterable(obj) and not cpython.PyTuple_Check(obj)
 
 
 cdef _get_array_shape(object obj, int32_t *dims, int32_t *ndims):
@@ -56,7 +61,7 @@ cdef _get_array_shape(object obj, int32_t *dims, int32_t *ndims):
     dims[ndims[0] - 1] = <int32_t>mylen
 
     for elem in obj:
-        if _is_sub_array(elem):
+        if _is_sub_array_iterable(elem):
             if elemlen == -2:
                 elemlen = len(elem)
                 if elemlen > _MAXINT32:
@@ -101,9 +106,9 @@ cdef inline array_encode(ConnectionSettings settings, WriteBuffer buf,
         int32_t ndims = 1
         int32_t i
 
-    if not _is_container(obj):
+    if not _is_array_iterable(obj):
         raise TypeError(
-            'a non-trivial iterable expected (got type {!r})'.format(
+            'a sized iterable container expected (got type {!r})'.format(
                 type(obj).__name__))
 
     _get_array_shape(obj, dims, &ndims)
@@ -247,9 +252,9 @@ cdef inline textarray_encode(ConnectionSettings settings, WriteBuffer buf,
         int32_t ndims = 1
         int32_t i
 
-    if not _is_container(obj):
+    if not _is_array_iterable(obj):
         raise TypeError(
-            'a non-trivial iterable expected (got type {!r})'.format(
+            'a sized iterable container expected (got type {!r})'.format(
                 type(obj).__name__))
 
     _get_array_shape(obj, dims, &ndims)

tests/test_codecs.py

@@ -661,6 +661,27 @@ async def test_arrays(self):
 
                 self.assertEqual(result, case, err_msg)
 
+        # A sized iterable is fine as array input.
+        class Iterable:
+            def __iter__(self):
+                return iter([1, 2, 3])
+
+            def __len__(self):
+                return 3
+
+        result = await self.con.fetchval("SELECT $1::int[]", Iterable())
+        self.assertEqual(result, [1, 2, 3])
+
+        # A pure container is _not_ OK for array input.
+        class SomeContainer:
+            def __contains__(self, item):
+                return False
+
+        with self.assertRaisesRegex(TypeError,
+                                    'sized iterable container expected'):
+            result = await self.con.fetchval("SELECT $1::int[]",
+                                             SomeContainer())
+
         with self.assertRaisesRegex(ValueError, 'dimensions'):
             await self.con.fetchval(
                 "SELECT $1::int[]",
@@ -687,7 +708,7 @@ async def test_arrays(self):
                 [[1], ['t'], [2]])
 
         with self.assertRaisesRegex(TypeError,
-                                    'non-trivial iterable expected'):
+                                    'sized iterable container expected'):
             await self.con.fetchval(
                 "SELECT $1::int[]",
                 1)