Addressed issue #418

An edge case with a reference definition has now been handled. Also added a schema nil check, to prevent a NPE seenin the wild.

Author: daveshanley

document_test.go

@@ -1454,3 +1454,20 @@ components:
 	_, errs := doc.BuildV3Model()
 	assert.Len(t, errs, 0)
 }
+
+func TestDocument_Issue418(t *testing.T) {
+
+	spec, _ := os.ReadFile("test_specs/nested_files/openapi-issue-418.yaml")
+
+	doc, err := NewDocumentWithConfiguration(spec, &datamodel.DocumentConfiguration{
+		AllowFileReferences: true,
+		BasePath:            "test_specs/nested_files",
+		SpecFilePath:        "test_specs/nested_files/openapi-issue-418.yaml",
+	})
+	if err != nil {
+		panic(err)
+	}
+	m, errs := doc.BuildV3Model()
+	assert.Len(t, errs, 0)
+	assert.Len(t, m.Model.Index.GetResolver().GetResolvingErrors(), 0)
+}

index/search_index.go

@@ -143,7 +143,12 @@ func (index *SpecIndex) SearchIndexForReferenceByReferenceWithContext(ctx contex
 		abp := index.GetSpecAbsolutePath()
 
 		if b == sfn && roloLookup == abp {
-			return nil, index, ctx
+			// if the reference is the same as the spec file name, we should look through the index for the component
+			var r *Reference
+			if len(uri) == 2 {
+				r = index.FindComponentInRoot(fmt.Sprintf("#/%s", uri[1]))
+			}
+			return r, index, ctx
 		}
 		rFile, err := index.rolodex.Open(roloLookup)
 		if err != nil {
@@ -169,7 +174,7 @@ func (index *SpecIndex) SearchIndexForReferenceByReferenceWithContext(ctx contex
 				}
 			}
 
-			if strings.HasSuffix(refParsed, n) {
+			if strings.HasSuffix(n, refParsed) {
 				node, _ := rFile.GetContentAsYAMLNode()
 				if node != nil {
 					r := &Reference{

test_specs/nested_files/components/foo.yaml

@@ -0,0 +1,12 @@
+# https://github.com/pb33f/libopenapi/issues/418
+get:
+  parameters:
+    - name: id
+      in: path
+      description: user id
+      required: true
+      schema:
+        type: string
+  responses:
+    '200':
+      $ref: '../openapi-issue-418.yaml#/components/responses/successResponse'

test_specs/nested_files/openapi-issue-418.yaml

@@ -0,0 +1,14 @@
+openapi: '3.0.3'
+paths:
+  '/foo':
+    $ref: './components/foo.yaml'
+components:
+  responses:
+    successResponse:
+      description: "success"
+      content:
+        application/json:
+          schema:
+            properties:
+              message:
+                type: string

what-changed/model/schema.go

@@ -50,6 +50,9 @@ type SchemaChanges struct {
 }
 
 func (s *SchemaChanges) GetPropertyChanges() []*Change {
+	if s == nil {
+		return nil
+	}
 	changes := s.Changes
 	if s.SchemaPropertyChanges != nil {
 		for n := range s.SchemaPropertyChanges {