From 717266ac15ef0a8754b89790c8be6fe35a2758b5 Mon Sep 17 00:00:00 2001
From: Willem Jan Noort <WillemJan.Noort@essent.nl>
Date: Tue, 10 Mar 2026 17:50:53 +0100
Subject: [PATCH] fix: add nullability to struct type String()

---
 arrow/avro/reader_test.go           |  5 ++---
 arrow/avro/schema_test.go           | 10 ++++-----
 arrow/datatype_nested.go            |  3 +++
 arrow/util/protobuf_reflect_test.go | 32 ++++++++++++++---------------
 4 files changed, 25 insertions(+), 25 deletions(-)

diff --git a/arrow/avro/reader_test.go b/arrow/avro/reader_test.go
index 9e4f36eb6..0eb513b34 100644
--- a/arrow/avro/reader_test.go
+++ b/arrow/avro/reader_test.go
@@ -101,9 +101,8 @@ func TestReader(t *testing.T) {
 							),
 						},
 						arrow.Field{
-							Name:     "mapfield",
-							Type:     arrow.MapOf(arrow.BinaryTypes.String, arrow.PrimitiveTypes.Int64),
-							Nullable: true,
+							Name: "mapfield",
+							Type: arrow.MapOf(arrow.BinaryTypes.String, arrow.PrimitiveTypes.Int64),
 						},
 						arrow.Field{
 							Name: "arrayField",
diff --git a/arrow/avro/schema_test.go b/arrow/avro/schema_test.go
index d813da00e..921e5e815 100644
--- a/arrow/avro/schema_test.go
+++ b/arrow/avro/schema_test.go
@@ -83,9 +83,8 @@ func TestSchemaStringEqual(t *testing.T) {
 					Name: "person",
 					Type: arrow.StructOf(
 						arrow.Field{
-							Name:     "lastname",
-							Type:     arrow.BinaryTypes.String,
-							Nullable: true,
+							Name: "lastname",
+							Type: arrow.BinaryTypes.String,
 						},
 						arrow.Field{
 							Name: "address",
@@ -101,9 +100,8 @@ func TestSchemaStringEqual(t *testing.T) {
 							),
 						},
 						arrow.Field{
-							Name:     "mapfield",
-							Type:     arrow.MapOf(arrow.BinaryTypes.String, arrow.PrimitiveTypes.Int64),
-							Nullable: true,
+							Name: "mapfield",
+							Type: arrow.MapOf(arrow.BinaryTypes.String, arrow.PrimitiveTypes.Int64),
 						},
 						arrow.Field{
 							Name: "arrayField",
diff --git a/arrow/datatype_nested.go b/arrow/datatype_nested.go
index 6664c505b..fd855d67f 100644
--- a/arrow/datatype_nested.go
+++ b/arrow/datatype_nested.go
@@ -444,6 +444,9 @@ func (t *StructType) String() string {
 			o.WriteString(", ")
 		}
 		o.WriteString(fmt.Sprintf("%s: %v", f.Name, f.Type))
+		if f.Nullable {
+			o.WriteString(" nullable")
+		}
 	}
 	o.WriteString(">")
 	return o.String()
diff --git a/arrow/util/protobuf_reflect_test.go b/arrow/util/protobuf_reflect_test.go
index 38297bb2d..35ef15692 100644
--- a/arrow/util/protobuf_reflect_test.go
+++ b/arrow/util/protobuf_reflect_test.go
@@ -119,14 +119,14 @@ func AllTheTypesFixture() Fixture {
     - bytes: type=binary, nullable
     - double: type=float64, nullable
     - enum: type=dictionary<values=utf8, indices=int32, ordered=false>, nullable
-    - message: type=struct<field1: utf8>, nullable
+    - message: type=struct<field1: utf8 nullable>, nullable
     - oneofstring: type=utf8, nullable
-    - oneofmessage: type=struct<field1: utf8>, nullable
-    - any: type=struct<field1: utf8>, nullable
+    - oneofmessage: type=struct<field1: utf8 nullable>, nullable
+    - any: type=struct<field1: utf8 nullable>, nullable
     - simple_map: type=map<int32, utf8, items_nullable>, nullable
-    - complex_map: type=map<utf8, struct<field1: utf8>, items_nullable>, nullable
+    - complex_map: type=map<utf8, struct<field1: utf8 nullable>, items_nullable>, nullable
     - simple_list: type=list<item: utf8, nullable>, nullable
-    - complex_list: type=list<item: struct<field1: utf8>, nullable>, nullable`
+    - complex_list: type=list<item: struct<field1: utf8 nullable>, nullable>, nullable`
 
 	return Fixture{
 		msg:     &msg,
@@ -255,13 +255,13 @@ func TestGetSchema(t *testing.T) {
     - bytes: type=binary, nullable
     - double: type=float64, nullable
     - enum: type=dictionary<values=utf8, indices=int32, ordered=false>, nullable
-    - message: type=struct<field1: utf8>, nullable
-    - oneof: type=dense_union<oneofstring: type=utf8, nullable=0, oneofmessage: type=struct<field1: utf8>, nullable=1>, nullable
-    - any: type=struct<field1: utf8>, nullable
+    - message: type=struct<field1: utf8 nullable>, nullable
+    - oneof: type=dense_union<oneofstring: type=utf8, nullable=0, oneofmessage: type=struct<field1: utf8 nullable>, nullable=1>, nullable
+    - any: type=struct<field1: utf8 nullable>, nullable
     - simple_map: type=map<int32, utf8, items_nullable>, nullable
-    - complex_map: type=map<utf8, struct<field1: utf8>, items_nullable>, nullable
+    - complex_map: type=map<utf8, struct<field1: utf8 nullable>, items_nullable>, nullable
     - simple_list: type=list<item: utf8, nullable>, nullable
-    - complex_list: type=list<item: struct<field1: utf8>, nullable>, nullable`
+    - complex_list: type=list<item: struct<field1: utf8 nullable>, nullable>, nullable`
 	CheckSchema(t, pmr, want)
 
 	excludeComplex := func(pfr *ProtobufFieldReflection) bool {
@@ -386,8 +386,8 @@ func TestExcludedNested(t *testing.T) {
 	}
 	schema := `schema:
   fields: 2
-    - simple_a: type=list<item: struct<field1: utf8>, nullable>, nullable
-    - simple_b: type=list<item: struct<field1: utf8>, nullable>, nullable`
+    - simple_a: type=list<item: struct<field1: utf8 nullable>, nullable>, nullable
+    - simple_b: type=list<item: struct<field1: utf8 nullable>, nullable>, nullable`
 
 	simpleNested := util_message.SimpleNested{
 		SimpleA: []*util_message.ExampleMessage{&msg},
@@ -415,8 +415,8 @@ func TestExcludedNested(t *testing.T) {
 	f := AllTheTypesNoAnyFixture()
 	schema = `schema:
   fields: 2
-    - all_the_types_no_any_a: type=list<item: struct<str: utf8, int32: int32, int64: int64, sint32: int32, sin64: int64, uint32: uint32, uint64: uint64, fixed32: uint32, fixed64: uint64, sfixed32: int32, bool: bool, bytes: binary, double: float64, enum: dictionary<values=utf8, indices=int32, ordered=false>, message: struct<field1: utf8>, oneofstring: utf8, oneofmessage: struct<field1: utf8>, simple_map: map<int32, utf8, items_nullable>, complex_map: map<utf8, struct<field1: utf8>, items_nullable>, simple_list: list<item: utf8, nullable>, complex_list: list<item: struct<field1: utf8>, nullable>>, nullable>, nullable
-    - all_the_types_no_any_b: type=list<item: struct<str: utf8, int32: int32, int64: int64, sint32: int32, sin64: int64, uint32: uint32, uint64: uint64, fixed32: uint32, fixed64: uint64, sfixed32: int32, bool: bool, bytes: binary, double: float64, enum: dictionary<values=utf8, indices=int32, ordered=false>, message: struct<field1: utf8>, oneofstring: utf8, oneofmessage: struct<field1: utf8>, simple_map: map<int32, utf8, items_nullable>, complex_map: map<utf8, struct<field1: utf8>, items_nullable>, simple_list: list<item: utf8, nullable>, complex_list: list<item: struct<field1: utf8>, nullable>>, nullable>, nullable`
+    - all_the_types_no_any_a: type=list<item: struct<str: utf8 nullable, int32: int32 nullable, int64: int64 nullable, sint32: int32 nullable, sin64: int64 nullable, uint32: uint32 nullable, uint64: uint64 nullable, fixed32: uint32 nullable, fixed64: uint64 nullable, sfixed32: int32 nullable, bool: bool nullable, bytes: binary nullable, double: float64 nullable, enum: dictionary<values=utf8, indices=int32, ordered=false> nullable, message: struct<field1: utf8 nullable> nullable, oneofstring: utf8 nullable, oneofmessage: struct<field1: utf8 nullable> nullable, simple_map: map<int32, utf8, items_nullable> nullable, complex_map: map<utf8, struct<field1: utf8 nullable>, items_nullable> nullable, simple_list: list<item: utf8, nullable> nullable, complex_list: list<item: struct<field1: utf8 nullable>, nullable> nullable>, nullable>, nullable
+    - all_the_types_no_any_b: type=list<item: struct<str: utf8 nullable, int32: int32 nullable, int64: int64 nullable, sint32: int32 nullable, sin64: int64 nullable, uint32: uint32 nullable, uint64: uint64 nullable, fixed32: uint32 nullable, fixed64: uint64 nullable, sfixed32: int32 nullable, bool: bool nullable, bytes: binary nullable, double: float64 nullable, enum: dictionary<values=utf8, indices=int32, ordered=false> nullable, message: struct<field1: utf8 nullable> nullable, oneofstring: utf8 nullable, oneofmessage: struct<field1: utf8 nullable> nullable, simple_map: map<int32, utf8, items_nullable> nullable, complex_map: map<utf8, struct<field1: utf8 nullable>, items_nullable> nullable, simple_list: list<item: utf8, nullable> nullable, complex_list: list<item: struct<field1: utf8 nullable>, nullable> nullable>, nullable>, nullable`
 
 	complexNested := util_message.ComplexNested{
 		AllTheTypesNoAnyA: []*util_message.AllTheTypesNoAny{f.msg.(*util_message.AllTheTypesNoAny)},
@@ -445,8 +445,8 @@ func TestExcludedNested(t *testing.T) {
 
 	schema = `schema:
   fields: 2
-    - complex_nested: type=struct<all_the_types_no_any_a: list<item: struct<str: utf8, int32: int32, int64: int64, sint32: int32, sin64: int64, uint32: uint32, uint64: uint64, fixed32: uint32, fixed64: uint64, sfixed32: int32, bool: bool, bytes: binary, double: float64, enum: dictionary<values=utf8, indices=int32, ordered=false>, message: struct<field1: utf8>, oneofstring: utf8, oneofmessage: struct<field1: utf8>, simple_map: map<int32, utf8, items_nullable>, complex_map: map<utf8, struct<field1: utf8>, items_nullable>, simple_list: list<item: utf8, nullable>, complex_list: list<item: struct<field1: utf8>, nullable>>, nullable>, all_the_types_no_any_b: list<item: struct<str: utf8, int32: int32, int64: int64, sint32: int32, sin64: int64, uint32: uint32, uint64: uint64, fixed32: uint32, fixed64: uint64, sfixed32: int32, bool: bool, bytes: binary, double: float64, enum: dictionary<values=utf8, indices=int32, ordered=false>, message: struct<field1: utf8>, oneofstring: utf8, oneofmessage: struct<field1: utf8>, simple_map: map<int32, utf8, items_nullable>, complex_map: map<utf8, struct<field1: utf8>, items_nullable>, simple_list: list<item: utf8, nullable>, complex_list: list<item: struct<field1: utf8>, nullable>>, nullable>>, nullable
-    - simple_nested: type=struct<simple_a: list<item: struct<field1: utf8>, nullable>, simple_b: list<item: struct<field1: utf8>, nullable>>, nullable`
+    - complex_nested: type=struct<all_the_types_no_any_a: list<item: struct<str: utf8 nullable, int32: int32 nullable, int64: int64 nullable, sint32: int32 nullable, sin64: int64 nullable, uint32: uint32 nullable, uint64: uint64 nullable, fixed32: uint32 nullable, fixed64: uint64 nullable, sfixed32: int32 nullable, bool: bool nullable, bytes: binary nullable, double: float64 nullable, enum: dictionary<values=utf8, indices=int32, ordered=false> nullable, message: struct<field1: utf8 nullable> nullable, oneofstring: utf8 nullable, oneofmessage: struct<field1: utf8 nullable> nullable, simple_map: map<int32, utf8, items_nullable> nullable, complex_map: map<utf8, struct<field1: utf8 nullable>, items_nullable> nullable, simple_list: list<item: utf8, nullable> nullable, complex_list: list<item: struct<field1: utf8 nullable>, nullable> nullable>, nullable> nullable, all_the_types_no_any_b: list<item: struct<str: utf8 nullable, int32: int32 nullable, int64: int64 nullable, sint32: int32 nullable, sin64: int64 nullable, uint32: uint32 nullable, uint64: uint64 nullable, fixed32: uint32 nullable, fixed64: uint64 nullable, sfixed32: int32 nullable, bool: bool nullable, bytes: binary nullable, double: float64 nullable, enum: dictionary<values=utf8, indices=int32, ordered=false> nullable, message: struct<field1: utf8 nullable> nullable, oneofstring: utf8 nullable, oneofmessage: struct<field1: utf8 nullable> nullable, simple_map: map<int32, utf8, items_nullable> nullable, complex_map: map<utf8, struct<field1: utf8 nullable>, items_nullable> nullable, simple_list: list<item: utf8, nullable> nullable, complex_list: list<item: struct<field1: utf8 nullable>, nullable> nullable>, nullable> nullable>, nullable
+    - simple_nested: type=struct<simple_a: list<item: struct<field1: utf8 nullable>, nullable> nullable, simple_b: list<item: struct<field1: utf8 nullable>, nullable> nullable>, nullable`
 
 	deepNested := util_message.DeepNested{
 		ComplexNested: &complexNested,