fix: component extension merge

PR #269 introduces a bug with the upgrade of kin-openapi. Component
extensions are not correctly identified and considered as part of
merging specs. However, a nil pointer exception can occur when no
extensions are specified as part of a spec.

This PR correctly handles this nil pointer and add tests to validate
behaviour.

merge.go

@@ -58,6 +58,9 @@ func mergeTags(dst, src *openapi3.T, replace bool) {
 }
 
 func initDestinationComponents(dst, src *openapi3.T) {
+	if src.Components.Extensions != nil && dst.Components.Extensions == nil {
+		dst.Components.Extensions = make(map[string]interface{})
+	}
 	if src.Components.Schemas != nil && dst.Components.Schemas == nil {
 		dst.Components.Schemas = make(map[string]*openapi3.SchemaRef)
 	}

merge_test.go

@@ -30,6 +30,10 @@ func TestMergeComponents(t *testing.T) {
 		dst := mustLoadFile(c, "merge_test_dst.yaml")
 		vervet.Merge(dst, src, false)
 
+		c.Assert(dst.Components.Extensions["x-snyk-extension-0"], openapiCmp, dstOrig.Components.Extensions["x-snyk-extension-0"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-1"], openapiCmp, dstOrig.Components.Extensions["x-snyk-extension-1"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-2"], openapiCmp, src.Components.Extensions["x-snyk-extension-2"])
+
 		c.Assert(dst.Components.Schemas["Foo"], openapiCmp, dstOrig.Components.Schemas["Foo"])
 		c.Assert(dst.Components.Schemas["Bar"], openapiCmp, src.Components.Schemas["Bar"])
 		c.Assert(dst.Components.Schemas["Baz"], openapiCmp, dstOrig.Components.Schemas["Baz"])
@@ -66,6 +70,10 @@ func TestMergeComponents(t *testing.T) {
 		dst := mustLoadFile(c, "merge_test_dst.yaml")
 		vervet.Merge(dst, src, true)
 
+		c.Assert(dst.Components.Extensions["x-snyk-extension-0"], openapiCmp, dstOrig.Components.Extensions["x-snyk-extension-0"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-1"], openapiCmp, src.Components.Extensions["x-snyk-extension-1"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-2"], openapiCmp, src.Components.Extensions["x-snyk-extension-2"])
+
 		c.Assert(dst.Components.Schemas["Foo"], openapiCmp, src.Components.Schemas["Foo"])
 		c.Assert(dst.Components.Schemas["Bar"], openapiCmp, src.Components.Schemas["Bar"])
 		c.Assert(dst.Components.Schemas["Baz"], openapiCmp, dstOrig.Components.Schemas["Baz"])
@@ -102,6 +110,10 @@ func TestMergeComponents(t *testing.T) {
 		dst := mustLoadFile(c, "merge_test_dst_missing_components.yaml")
 		vervet.Merge(dst, src, true)
 
+		c.Assert(dst.Components.Extensions["x-snyk-extension-0"], openapiCmp, dstOrig.Components.Extensions["x-snyk-extension-0"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-1"], openapiCmp, src.Components.Extensions["x-snyk-extension-1"])
+		c.Assert(dst.Components.Extensions["x-snyk-extension-2"], openapiCmp, src.Components.Extensions["x-snyk-extension-2"])
+
 		c.Assert(dst.Components.Schemas["Foo"], openapiCmp, src.Components.Schemas["Foo"])
 		c.Assert(dst.Components.Schemas["Bar"], openapiCmp, src.Components.Schemas["Bar"])
 		c.Assert(dst.Components.Schemas["Baz"], openapiCmp, dstOrig.Components.Schemas["Baz"])

testdata/merge_test_dst.yaml

@@ -1,4 +1,6 @@
 components:
+  x-snyk-extension-0: "extension-0"
+  x-snyk-extension-1: "extension-1"
   schemas:
     Foo:
       type: object
@@ -73,6 +75,3 @@ components:
      value: foo-natured
     Baz:
      value: bazil
-  x-extension:
-    key0: value0
-    key1: value1

testdata/merge_test_src.yaml

@@ -1,4 +1,6 @@
 components:
+  x-snyk-extension-1: "extension-11"
+  x-snyk-extension-2: "extension-2"
   schemas:
     Foo:
       type: object
@@ -69,6 +71,3 @@ components:
      value: foo
     Bar:
      value: bar
-  x-extension:
-    key1: value11
-    key2: value2

versionware/example/releases/embed.go

@@ -4,12 +4,11 @@ import "embed"
 
 // Embed compiled OpenAPI specs in Go projects.
 
-// Versions contains OpenAPI specs for each distinct release version.
-//
 //go:embed 2021-11-01~experimental/spec.json
 //go:embed 2021-11-01~experimental/spec.yaml
 //go:embed 2021-11-08~experimental/spec.json
 //go:embed 2021-11-08~experimental/spec.yaml
 //go:embed 2021-11-20~experimental/spec.json
 //go:embed 2021-11-20~experimental/spec.yaml
+// Versions contains OpenAPI specs for each distinct release version.
 var Versions embed.FS