feat: add attribute to schema model

datamodel/high/base/schema.go

@@ -5,9 +5,10 @@ package base
 
 import (
 	"fmt"
-	"gopkg.in/yaml.v3"
 	"sync"
 
+	"gopkg.in/yaml.v3"
+
 	"github.com/pb33f/libopenapi/datamodel/high"
 	lowmodel "github.com/pb33f/libopenapi/datamodel/low"
 	"github.com/pb33f/libopenapi/datamodel/low/base"
@@ -68,6 +69,9 @@ type Schema struct {
 	// in 3.1 Items can be a Schema or a boolean
 	Items *DynamicValue[*SchemaProxy, bool] `json:"items,omitempty" yaml:"items,omitempty"`
 
+	// 3.1 only, part of the JSON Schema spec provides a way to identify a subschema
+	Anchor string `json:"$anchor,omitempty" yaml:"$anchor,omitempty"`
+
 	// Compatible with all versions
 	Not                  *SchemaProxy            `json:"not,omitempty" yaml:"not,omitempty"`
 	Properties           map[string]*SchemaProxy `json:"properties,omitempty" yaml:"properties,omitempty"`
@@ -282,6 +286,10 @@ func NewSchema(schema *base.Schema) *Schema {
 	}
 	s.Enum = enum
 
+	if !schema.Anchor.IsEmpty() {
+		s.Anchor = schema.Anchor.Value
+	}
+
 	// async work.
 	// any polymorphic properties need to be handled in their own threads
 	// any properties each need to be processed in their own thread.

datamodel/high/base/schema_test.go

@@ -266,7 +266,8 @@ minLength: 1
 maxItems: 20
 minItems: 10
 maxProperties: 30
-minProperties: 1`
+minProperties: 1
+$anchor: anchor`
 
 	var compNode yaml.Node
 	_ = yaml.Unmarshal([]byte(testSpec), &compNode)
@@ -310,6 +311,7 @@ minProperties: 1`
 	assert.True(t, compiled.WriteOnly)
 	assert.True(t, *compiled.Deprecated)
 	assert.True(t, *compiled.Nullable)
+	assert.Equal(t, "anchor", compiled.Anchor)
 
 	wentLow := compiled.GoLow()
 	assert.Equal(t, 129, wentLow.AdditionalProperties.ValueNode.Line)
@@ -317,8 +319,7 @@ minProperties: 1`
 
 	// now render it out!
 	schemaBytes, _ := compiled.Render()
-	assert.Len(t, schemaBytes, 3460)
-
+	assert.Len(t, schemaBytes, 3476)
 }
 
 func TestSchemaObjectWithAllOfSequenceOrder(t *testing.T) {

datamodel/low/base/constants.go

@@ -44,6 +44,7 @@ const (
 	ExclusiveMaximumLabel      = "exclusiveMaximum"
 	SchemaLabel                = "schema"
 	SchemaTypeLabel            = "$schema"
+	AnchorLabel                = "$anchor"
 )
 
 /*

datamodel/low/base/schema.go

@@ -90,6 +90,7 @@ type Schema struct {
 	PropertyNames         low.NodeReference[*SchemaProxy]
 	UnevaluatedItems      low.NodeReference[*SchemaProxy]
 	UnevaluatedProperties low.NodeReference[*SchemaProxy]
+	Anchor                low.NodeReference[string]
 
 	// Compatible with all versions
 	Title                low.NodeReference[string]
@@ -394,6 +395,9 @@ func (s *Schema) Hash() [32]byte {
 	if !s.UnevaluatedItems.IsEmpty() {
 		d = append(d, low.GenerateHashString(s.UnevaluatedItems.Value))
 	}
+	if !s.Anchor.IsEmpty() {
+		d = append(d, fmt.Sprint(s.Anchor.Value))
+	}
 
 	depSchemasKeys := make([]string, len(s.DependentSchemas.Value))
 	z = 0
@@ -514,6 +518,7 @@ func (s *Schema) GetExtensions() map[low.KeyReference[string]]low.ValueReference
 //   - PropertyNames
 //   - UnevaluatedItems
 //   - UnevaluatedProperties
+//   - Anchor
 func (s *Schema) Build(root *yaml.Node, idx *index.SpecIndex) error {
 	s.Reference = new(low.Reference)
 	if h, _, _ := utils.IsNodeRefValue(root); h {
@@ -615,6 +620,14 @@ func (s *Schema) Build(root *yaml.Node, idx *index.SpecIndex) error {
 		}
 	}
 
+	// handle anchor if set. (3.1)
+	_, anchorLabel, anchorNode := utils.FindKeyNodeFullTop(AnchorLabel, root.Content)
+	if anchorNode != nil {
+		s.Anchor = low.NodeReference[string]{
+			Value: anchorNode.Value, KeyNode: anchorLabel, ValueNode: anchorLabel,
+		}
+	}
+
 	// handle example if set. (3.0)
 	_, expLabel, expNode := utils.FindKeyNodeFull(ExampleLabel, root.Content)
 	if expNode != nil {

datamodel/low/base/schema_test.go

@@ -150,7 +150,8 @@ examples:
 contains:
   type: int
 maxContains: 10
-minContains: 1`
+minContains: 1
+$anchor: anchor`
 }
 
 func Test_Schema(t *testing.T) {
@@ -308,6 +309,7 @@ func Test_Schema(t *testing.T) {
 	assert.Equal(t, "string", sch.PropertyNames.Value.Schema().Type.Value.A)
 	assert.Equal(t, "boolean", sch.UnevaluatedItems.Value.Schema().Type.Value.A)
 	assert.Equal(t, "integer", sch.UnevaluatedProperties.Value.Schema().Type.Value.A)
+	assert.Equal(t, "anchor", sch.Anchor.Value)
 }
 
 func TestSchemaAllOfSequenceOrder(t *testing.T) {

datamodel/low/v3/constants.go

@@ -136,4 +136,5 @@ const (
 	UnevaluatedPropertiesLabel = "unevaluatedProperties"
 	DependentSchemasLabel      = "dependentSchemas"
 	PatternPropertiesLabel     = "patternProperties"
+	AnchorLabel                = "$anchor"
 )