Fix set_type_codec() to accept standard SQL type names (#619)

Currently, `Connection.set_type_codec()` only accepts type names as they
appear in `pg_catalog.pg_type` and would refuse to handle a standard SQL
spelling of a type like `character varying`.  This is an oversight, as
the internal type names aren't really supposed to be treated as public
Postgres API.  Additionally, for historical reasons, Postgres has a
single-byte `"char"` type, which is distinct from both `varchar` and
SQL `char`, which may lead to massive confusion if a user sets up a
custom codec on it expecting to handle the `char(n)` type instead.

Issue: #617

Author: elprans

asyncpg/connection.py

@@ -428,6 +428,32 @@ async def _introspect_types(self, typeoids, timeout):
         return await self.__execute(
             self._intro_query, (list(typeoids),), 0, timeout)
 
+    async def _introspect_type(self, typename, schema):
+        if (
+            schema == 'pg_catalog'
+            and typename.lower() in protocol.BUILTIN_TYPE_NAME_MAP
+        ):
+            typeoid = protocol.BUILTIN_TYPE_NAME_MAP[typename.lower()]
+            rows = await self._execute(
+                introspection.TYPE_BY_OID,
+                [typeoid],
+                limit=0,
+                timeout=None,
+            )
+            if rows:
+                typeinfo = rows[0]
+            else:
+                typeinfo = None
+        else:
+            typeinfo = await self.fetchrow(
+                introspection.TYPE_BY_NAME, typename, schema)
+
+        if not typeinfo:
+            raise ValueError(
+                'unknown type: {}.{}'.format(schema, typename))
+
+        return typeinfo
+
     def cursor(
         self,
         query,
@@ -1110,12 +1136,7 @@ async def set_type_codec(self, typename, *,
             ``format``.
         """
         self._check_open()
-
-        typeinfo = await self.fetchrow(
-            introspection.TYPE_BY_NAME, typename, schema)
-        if not typeinfo:
-            raise ValueError('unknown type: {}.{}'.format(schema, typename))
-
+        typeinfo = await self._introspect_type(typename, schema)
         if not introspection.is_scalar_type(typeinfo):
             raise ValueError(
                 'cannot use custom codec on non-scalar type {}.{}'.format(
@@ -1142,15 +1163,9 @@ async def reset_type_codec(self, typename, *, schema='public'):
         .. versionadded:: 0.12.0
         """
 
-        typeinfo = await self.fetchrow(
-            introspection.TYPE_BY_NAME, typename, schema)
-        if not typeinfo:
-            raise ValueError('unknown type: {}.{}'.format(schema, typename))
-
-        oid = typeinfo['oid']
-
+        typeinfo = await self._introspect_type(typename, schema)
         self._protocol.get_settings().remove_python_codec(
-            oid, typename, schema)
+            typeinfo['oid'], typename, schema)
 
         # Statement cache is no longer valid due to codec changes.
         self._drop_local_statement_cache()
@@ -1191,13 +1206,7 @@ async def set_builtin_type_codec(self, typename, *,
             core data type.  Added the *format* keyword argument.
         """
         self._check_open()
-
-        typeinfo = await self.fetchrow(
-            introspection.TYPE_BY_NAME, typename, schema)
-        if not typeinfo:
-            raise exceptions.InterfaceError(
-                'unknown type: {}.{}'.format(schema, typename))
-
+        typeinfo = await self._introspect_type(typename, schema)
         if not introspection.is_scalar_type(typeinfo):
             raise exceptions.InterfaceError(
                 'cannot alias non-scalar type {}.{}'.format(

asyncpg/introspection.py

@@ -147,6 +147,18 @@
 '''
 
 
+TYPE_BY_OID = '''\
+SELECT
+    t.oid,
+    t.typelem     AS elemtype,
+    t.typtype     AS kind
+FROM
+    pg_catalog.pg_type AS t
+WHERE
+    t.oid = $1
+'''
+
+
 # 'b' for a base type, 'd' for a domain, 'e' for enum.
 SCALAR_TYPE_KINDS = (b'b', b'd', b'e')
 

asyncpg/protocol/__init__.py

@@ -4,5 +4,6 @@
 # This module is part of asyncpg and is released under
 # the Apache 2.0 License: http://www.apache.org/licenses/LICENSE-2.0
 
+# flake8: NOQA
 
-from .protocol import Protocol, Record, NO_TIMEOUT  # NOQA
+from .protocol import Protocol, Record, NO_TIMEOUT, BUILTIN_TYPE_NAME_MAP

asyncpg/protocol/pgtypes.pxi

@@ -216,5 +216,23 @@ BUILTIN_TYPE_NAME_MAP['double precision'] = \
 BUILTIN_TYPE_NAME_MAP['timestamp with timezone'] = \
     BUILTIN_TYPE_NAME_MAP['timestamptz']
 
+BUILTIN_TYPE_NAME_MAP['timestamp without timezone'] = \
+    BUILTIN_TYPE_NAME_MAP['timestamp']
+
 BUILTIN_TYPE_NAME_MAP['time with timezone'] = \
     BUILTIN_TYPE_NAME_MAP['timetz']
+
+BUILTIN_TYPE_NAME_MAP['time without timezone'] = \
+    BUILTIN_TYPE_NAME_MAP['time']
+
+BUILTIN_TYPE_NAME_MAP['char'] = \
+    BUILTIN_TYPE_NAME_MAP['bpchar']
+
+BUILTIN_TYPE_NAME_MAP['character'] = \
+    BUILTIN_TYPE_NAME_MAP['bpchar']
+
+BUILTIN_TYPE_NAME_MAP['character varying'] = \
+    BUILTIN_TYPE_NAME_MAP['varchar']
+
+BUILTIN_TYPE_NAME_MAP['bit varying'] = \
+    BUILTIN_TYPE_NAME_MAP['varbit']

tests/test_codecs.py

@@ -1255,6 +1255,39 @@ async def test_custom_codec_on_domain(self):
         finally:
             await self.con.execute('DROP DOMAIN custom_codec_t')
 
+    async def test_custom_codec_on_stdsql_types(self):
+        types = [
+            'smallint',
+            'int',
+            'integer',
+            'bigint',
+            'decimal',
+            'real',
+            'double precision',
+            'timestamp with timezone',
+            'time with timezone',
+            'timestamp without timezone',
+            'time without timezone',
+            'char',
+            'character',
+            'character varying',
+            'bit varying',
+            'CHARACTER VARYING'
+        ]
+
+        for t in types:
+            with self.subTest(type=t):
+                try:
+                    await self.con.set_type_codec(
+                        t,
+                        schema='pg_catalog',
+                        encoder=str,
+                        decoder=str,
+                        format='text'
+                    )
+                finally:
+                    await self.con.reset_type_codec(t, schema='pg_catalog')
+
     async def test_custom_codec_on_enum(self):
         """Test encoding/decoding using a custom codec on an enum."""
         await self.con.execute('''