From 82da6e2aa7869db1c22f1bc3b04b3d54e254991c Mon Sep 17 00:00:00 2001
From: Omer E <33223663+tcdsv@users.noreply.github.com>
Date: Wed, 15 Nov 2023 22:02:35 +0200
Subject: [PATCH] flatten Default field (#432)

fixes https://github.com/Tufin/oasdiff/issues/431
---
 flatten/merge_allof.go      |  30 ++++++++-
 flatten/merge_allof_test.go | 121 ++++++++++++++++++++++++++++++++++++
 2 files changed, 149 insertions(+), 2 deletions(-)

diff --git a/flatten/merge_allof.go b/flatten/merge_allof.go
index 928e9814..00790efa 100644
--- a/flatten/merge_allof.go
+++ b/flatten/merge_allof.go
@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"reflect"
 	"regexp"
 	"strings"
 
@@ -13,7 +14,7 @@ import (
 const (
 	FormatErrorMessage  = "unable to resolve Format conflict using default resolver: all Format values must be identical"
 	TypeErrorMessage    = "unable to resolve Type conflict: all Type values must be identical"
-	FormatResolverError = ""
+	DefaultErrorMessage = "unable to resolve Default conflict: all Default values must be identical"
 
 	FormatInt32  = "int32"
 	FormatInt64  = "int64"
@@ -50,6 +51,7 @@ type SchemaCollection struct {
 	Nullable             []bool
 	ReadOnly             []bool
 	WriteOnly            []bool
+	Default              []interface{}
 }
 
 type state struct {
@@ -137,6 +139,7 @@ func mergeInternal(state *state, base *openapi3.SchemaRef) (*openapi3.SchemaRef,
 	result.Value.Max = base.Value.Max
 	result.Value.MultipleOf = base.Value.MultipleOf
 	result.Value.MinLength = base.Value.MinLength
+	result.Value.Default = base.Value.Default
 	if base.Value.MaxLength != nil {
 		result.Value.MaxLength = openapi3.Uint64Ptr(*base.Value.MaxLength)
 	}
@@ -301,7 +304,10 @@ func flattenSchemas(state *state, result *openapi3.SchemaRef, schemas []*openapi
 	result.Value.Required = resolveRequired(collection.Required)
 	result.Value = resolveMultipleOf(result.Value, &collection)
 	result.Value.UniqueItems = resolveUniqueItems(collection.UniqueItems)
-
+	result.Value.Default, err = resolveDefault(&collection)
+	if err != nil {
+		return err
+	}
 	result.Value.Enum, err = resolveEnum(collection.Enum)
 	if err != nil {
 		return err
@@ -873,6 +879,7 @@ func collect(schemas []*openapi3.SchemaRef) SchemaCollection {
 		collection.Nullable = append(collection.Nullable, s.Value.Nullable)
 		collection.ReadOnly = append(collection.ReadOnly, s.Value.ReadOnly)
 		collection.WriteOnly = append(collection.WriteOnly, s.Value.WriteOnly)
+		collection.Default = append(collection.Default, s.Value.Default)
 	}
 	return collection
 }
@@ -1008,3 +1015,22 @@ func findIntersection(arrays ...[]string) []string {
 
 	return intersection
 }
+
+func resolveDefault(collection *SchemaCollection) (interface{}, error) {
+	values := make([]interface{}, 0)
+	for _, v := range collection.Default {
+		if v != nil {
+			values = append(values, v)
+		}
+	}
+	if len(values) == 0 {
+		return nil, nil
+	}
+	first := values[0]
+	for _, v := range values {
+		if !reflect.DeepEqual(first, v) {
+			return nil, errors.New(DefaultErrorMessage)
+		}
+	}
+	return first, nil
+}
diff --git a/flatten/merge_allof_test.go b/flatten/merge_allof_test.go
index 7ad5fb3b..99106da5 100644
--- a/flatten/merge_allof_test.go
+++ b/flatten/merge_allof_test.go
@@ -10,6 +10,127 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+// identical Default fields are merged successfully
+func TestMerge_Default(t *testing.T) {
+	merged, err := flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				Default: 10,
+			},
+		})
+
+	require.NoError(t, err)
+	require.Equal(t, 10, merged.Default)
+
+	merged, err = flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				AllOf: openapi3.SchemaRefs{
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type: "object",
+						},
+					},
+				},
+			},
+		})
+
+	require.NoError(t, err)
+	require.Nil(t, merged.AllOf)
+	require.Equal(t, nil, merged.Default)
+
+	merged, err = flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				AllOf: openapi3.SchemaRefs{
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: 10,
+						},
+					},
+				},
+			},
+		})
+
+	require.NoError(t, err)
+	require.Nil(t, merged.AllOf)
+	require.Equal(t, 10, merged.Default)
+
+	merged, err = flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				AllOf: openapi3.SchemaRefs{
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: 10,
+						},
+					},
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: 10,
+						},
+					},
+				},
+			},
+		})
+
+	require.NoError(t, err)
+	require.Nil(t, merged.AllOf)
+	require.Equal(t, 10, merged.Default)
+
+	merged, err = flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				AllOf: openapi3.SchemaRefs{
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: "abc",
+						},
+					},
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: "abc",
+						},
+					},
+				},
+			},
+		})
+
+	require.NoError(t, err)
+	require.Nil(t, merged.AllOf)
+	require.Equal(t, "abc", merged.Default)
+}
+
+// Conflicting Default values cannot be resolved
+func TestMerge_DefaultFailure(t *testing.T) {
+	_, err := flatten.Merge(
+		openapi3.SchemaRef{
+			Value: &openapi3.Schema{
+				AllOf: openapi3.SchemaRefs{
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: 10,
+						},
+					},
+					&openapi3.SchemaRef{
+						Value: &openapi3.Schema{
+							Type:    "object",
+							Default: "abc",
+						},
+					},
+				},
+			},
+		})
+
+	require.EqualError(t, err, flatten.DefaultErrorMessage)
+}
+
 // verify that if all ReadOnly fields are set to false, then the ReadOnly field in the merged schema is false.
 func TestMerge_ReadOnlyIsSetToFalse(t *testing.T) {
 	merged, err := flatten.Merge(