MagicStack · elprans · Nov 29, 2020 · Nov 27, 2020
diff --git a/asyncpg/exceptions/_base.py b/asyncpg/exceptions/_base.py
@@ -210,6 +210,15 @@ def __init__(self, msg, *, detail=None, hint=None):
        InterfaceMessage.__init__(self, detail=detail, hint=hint)
        Exception.__init__(self, msg)

+    def with_msg(self, msg):
+        return type(self)(
+            msg,
+            detail=self.detail,
+            hint=self.hint,
+        ).with_traceback(
+            self.__traceback__
+        )
+

 class DataError(InterfaceError, ValueError):
    """An error caused by invalid query input."""

diff --git a/asyncpg/protocol/codecs/record.pyx b/asyncpg/protocol/codecs/record.pyx
@@ -51,9 +51,20 @@ cdef anonymous_record_decode(ConnectionSettings settings, FRBuffer *buf):
    return result


+cdef anonymous_record_encode(ConnectionSettings settings, WriteBuffer buf, obj):
+    raise exceptions.UnsupportedClientFeatureError(
+        'input of anonymous composite types is not supported',
+        hint=(
+            'Consider declaring an explicit composite type and '
+            'using it to cast the argument.'
+        ),
+        detail='PostgreSQL does not implement anonymous composite type input.'
+    )
+
+
 cdef init_record_codecs():
    register_core_codec(RECORDOID,
-                        <encode_func>NULL,
+                        <encode_func>anonymous_record_encode,
                        <decode_func>anonymous_record_decode,
                        PG_FORMAT_BINARY)


diff --git a/asyncpg/protocol/prepared_stmt.pyx b/asyncpg/protocol/prepared_stmt.pyx
@@ -156,9 +156,11 @@ cdef class PreparedStatementState:
                except (AssertionError, exceptions.InternalClientError):
                    # These are internal errors and should raise as-is.
                    raise
-                except exceptions.InterfaceError:
-                    # This is already a descriptive error.
-                    raise
+                except exceptions.InterfaceError as e:
+                    # This is already a descriptive error, but annotate
+                    # with argument name for clarity.
+                    raise e.with_msg(
+                        f'query argument ${idx + 1}: {e.args[0]}') from None
                except Exception as e:
                    # Everything else is assumed to be an encoding error
                    # due to invalid input.

diff --git a/tests/test_codecs.py b/tests/test_codecs.py
@@ -876,6 +876,13 @@ async def test_composites(self):

        self.assertEqual(res, (None, 1234, '5678', (42, '42')))

+        with self.assertRaisesRegex(
+            asyncpg.UnsupportedClientFeatureError,
+            'query argument \\$1: input of anonymous '
+            'composite types is not supported',
+        ):
+            await self.con.fetchval("SELECT (1, 'foo') = $1", (1, 'foo'))
+
        try:
            st = await self.con.prepare('''
                SELECT ROW(