fix: propagate kwargs through compilation nodes

Fixes #1138

When we visit a struct or union, we are handed an IdentifierProvider. Before, we just used it at this first layer, but forgot to pass it down to lower compilation steps. Now, we pass it along. This was a problem when we encountered nested dtypes, eg struct<struct<>>

duckdb_engine/datatypes.py

@@ -233,7 +233,7 @@ def visit_struct(
     identifier_preparer: PGIdentifierPreparer,
     **kw: Any,
 ) -> str:
-    return "STRUCT" + struct_or_union(instance, compiler, identifier_preparer)
+    return "STRUCT" + struct_or_union(instance, compiler, identifier_preparer, **kw)
 
 
 @compiles(Union, "duckdb")  # type: ignore[misc]
@@ -243,21 +243,25 @@ def visit_union(
     identifier_preparer: PGIdentifierPreparer,
     **kw: Any,
 ) -> str:
-    return "UNION" + struct_or_union(instance, compiler, identifier_preparer)
+    return "UNION" + struct_or_union(instance, compiler, identifier_preparer, **kw)
 
 
 def struct_or_union(
     instance: typing.Union[Union, Struct],
     compiler: PGTypeCompiler,
     identifier_preparer: PGIdentifierPreparer,
+    **kw: Any,
 ) -> str:
     fields = instance.fields
     if fields is None:
         raise exc.CompileError(f"DuckDB {repr(instance)} type requires fields")
     return "({})".format(
         ", ".join(
             "{} {}".format(
-                identifier_preparer.quote_identifier(key), process_type(value, compiler)
+                identifier_preparer.quote_identifier(key),
+                process_type(
+                    value, compiler, identifier_preparer=identifier_preparer, **kw
+                ),
             )
             for key, value in fields.items()
         )
@@ -267,13 +271,14 @@ def struct_or_union(
 def process_type(
     value: typing.Union[TypeEngine, Type[TypeEngine]],
     compiler: PGTypeCompiler,
+    **kw: Any,
 ) -> str:
-    return compiler.process(type_api.to_instance(value))
+    return compiler.process(type_api.to_instance(value), **kw)
 
 
 @compiles(Map, "duckdb")  # type: ignore[misc]
 def visit_map(instance: Map, compiler: PGTypeCompiler, **kw: Any) -> str:
     return "MAP({}, {})".format(
-        process_type(instance.key_type, compiler),
-        process_type(instance.value_type, compiler),
+        process_type(instance.key_type, compiler, **kw),
+        process_type(instance.value_type, compiler, **kw),
     )

duckdb_engine/tests/test_datatypes.py

@@ -211,6 +211,29 @@ class Entry(base):
     assert result.map == map_data
 
 
+def test_double_nested_types(engine: Engine, session: Session) -> None:
+    """Test for https://github.com/Mause/duckdb_engine/issues/1138"""
+    importorskip("duckdb", "0.5.0")  # nested types require at least duckdb 0.5.0
+    base = declarative_base()
+
+    class Entry(base):
+        __tablename__ = "test_struct"
+
+        id = Column(Integer, primary_key=True, default=0)
+        outer = Column(Struct({"inner": Struct({"val": Integer})}))
+
+    base.metadata.create_all(bind=engine)
+
+    outer = {"inner": {"val": 42}}
+
+    session.add(Entry(outer=outer))  # type: ignore[call-arg]
+    session.commit()
+
+    result = session.query(Entry).one()
+
+    assert result.outer == outer
+
+
 def test_interval(engine: Engine, snapshot: SnapshotTest) -> None:
     test_table = Table("test_table", MetaData(), Column("duration", Interval))