From f2256f10a1d328fb924ca79cde76e77641398573 Mon Sep 17 00:00:00 2001
From: Vladimir Mihailenco <vladimir.webdev@gmail.com>
Date: Sun, 10 Sep 2023 10:26:57 +0300
Subject: [PATCH] fix: alloc when mounting (#891)

---
 internal/util.go      | 24 ++++++++++++++++++++++++
 model_table_struct.go |  3 ++-
 schema/field.go       |  5 +++--
 schema/reflect.go     | 24 ------------------------
 4 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/internal/util.go b/internal/util.go
index 641309725..66b92b3c5 100644
--- a/internal/util.go
+++ b/internal/util.go
@@ -55,3 +55,27 @@ func Unwrap(err error) error {
 	}
 	return u.Unwrap()
 }
+
+func FieldByIndexAlloc(v reflect.Value, index []int) reflect.Value {
+	if len(index) == 1 {
+		return v.Field(index[0])
+	}
+
+	for i, idx := range index {
+		if i > 0 {
+			v = indirectNil(v)
+		}
+		v = v.Field(idx)
+	}
+	return v
+}
+
+func indirectNil(v reflect.Value) reflect.Value {
+	if v.Kind() == reflect.Ptr {
+		if v.IsNil() {
+			v.Set(reflect.New(v.Type().Elem()))
+		}
+		v = v.Elem()
+	}
+	return v
+}
diff --git a/model_table_struct.go b/model_table_struct.go
index fadc9284c..65e076d23 100644
--- a/model_table_struct.go
+++ b/model_table_struct.go
@@ -8,6 +8,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/uptrace/bun/internal"
 	"github.com/uptrace/bun/schema"
 )
 
@@ -234,7 +235,7 @@ func (m *structTableModel) parentIndex() []int {
 }
 
 func (m *structTableModel) mount(host reflect.Value) {
-	m.strct = host.FieldByIndex(m.rel.Field.Index)
+	m.strct = internal.FieldByIndexAlloc(host, m.rel.Field.Index)
 	m.structInited = false
 }
 
diff --git a/schema/field.go b/schema/field.go
index 283a3b992..a3b086054 100644
--- a/schema/field.go
+++ b/schema/field.go
@@ -5,6 +5,7 @@ import (
 	"reflect"
 
 	"github.com/uptrace/bun/dialect"
+	"github.com/uptrace/bun/internal"
 	"github.com/uptrace/bun/internal/tagparser"
 )
 
@@ -50,7 +51,7 @@ func (f *Field) Clone() *Field {
 }
 
 func (f *Field) Value(strct reflect.Value) reflect.Value {
-	return fieldByIndexAlloc(strct, f.Index)
+	return internal.FieldByIndexAlloc(strct, f.Index)
 }
 
 func (f *Field) HasNilValue(v reflect.Value) bool {
@@ -117,7 +118,7 @@ func (f *Field) ScanValue(strct reflect.Value, src interface{}) error {
 		return nil
 	}
 
-	fv := fieldByIndexAlloc(strct, f.Index)
+	fv := internal.FieldByIndexAlloc(strct, f.Index)
 	return f.ScanWithCheck(fv, src)
 }
 
diff --git a/schema/reflect.go b/schema/reflect.go
index f13826a6c..89be8eeb6 100644
--- a/schema/reflect.go
+++ b/schema/reflect.go
@@ -46,27 +46,3 @@ func fieldByIndex(v reflect.Value, index []int) (_ reflect.Value, ok bool) {
 	}
 	return v, true
 }
-
-func fieldByIndexAlloc(v reflect.Value, index []int) reflect.Value {
-	if len(index) == 1 {
-		return v.Field(index[0])
-	}
-
-	for i, idx := range index {
-		if i > 0 {
-			v = indirectNil(v)
-		}
-		v = v.Field(idx)
-	}
-	return v
-}
-
-func indirectNil(v reflect.Value) reflect.Value {
-	if v.Kind() == reflect.Ptr {
-		if v.IsNil() {
-			v.Set(reflect.New(v.Type().Elem()))
-		}
-		v = v.Elem()
-	}
-	return v
-}