Raise proper error on anonymous composite input (tuple arguments) (MagicStack#664)

Currently asyncpg would crash with an arcane "could not resolve query result and/or argument types in 6 attempts", which isn't helpful. Do the right thing by raising an `UnsupportedClientFeatureError` explicitly instead. Fixes MagicStack#476.

Author: elprans

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."""

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)
 

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.

tests/test_codecs.py

@@ -892,6 +892,13 @@ 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(