Adding a simple dataref extension, similar to the java sdk

Signed-off-by: Matthias Wessendorf <[email protected]>
Signed-off-by: Doug Davis <[email protected]>

Author: matzew

Diff for: v2/extensions/dataref_extension.go

@@ -0,0 +1,41 @@
+/*
+ Copyright 2024 The CloudEvents Authors
+ SPDX-License-Identifier: Apache-2.0
+*/
+
+package extensions
+
+import (
+	"github.com/cloudevents/sdk-go/v2/event"
+	"net/url"
+)
+
+const DataRefExtensionKey = "dataref"
+
+// DataRefExtension represents the CloudEvents Dataref (claim check pattern)
+// extension for cloudevents contexts,
+// See https://github.com/cloudevents/spec/blob/main/cloudevents/extensions/dataref.md
+// for more info
+type DataRefExtension struct {
+	DataRef string `json:"dataref"`
+}
+
+// AddDataRefExtension adds the dataref attribute to the cloudevents context
+func AddDataRefExtension(e *event.Event, dataRef string) error {
+	if _, err := url.Parse(dataRef); err != nil {
+		return err
+	}
+	e.SetExtension(DataRefExtensionKey, dataRef)
+	return nil
+}
+
+// GetDataRefExtension returns any dataref attribute present in the
+// cloudevent event/context and a bool to indicate if it was found.
+// If not found, the DataRefExtension.DataRef value will be ""
+func GetDataRefExtension(e event.Event) (DataRefExtension, bool) {
+	if dataRefValue, ok := e.Extensions()[DataRefExtensionKey]; ok {
+		dataRefStr, _ := dataRefValue.(string)
+		return DataRefExtension{DataRef: dataRefStr}, true
+	}
+	return DataRefExtension{}, false
+}

Diff for: v2/extensions/dataref_extension_test.go

@@ -0,0 +1,69 @@
+/*
+ Copyright 2024 The CloudEvents Authors
+ SPDX-License-Identifier: Apache-2.0
+*/
+
+package extensions
+
+import (
+	"testing"
+
+	"github.com/cloudevents/sdk-go/v2/event"
+)
+
+func TestAddDataRefExtension(t *testing.T) {
+	// MUST HAVE AT LEAST ONE FAILING TEST as that'll also test to make sure
+	// that the failed add() call won't actually set anything
+
+	tests := []struct {
+		dataref string
+		pass    bool
+	}{
+		{"https://example.com/data", true},
+		{"://invalid-url", false},
+	}
+
+	for _, test := range tests {
+		e := event.New()
+		err := AddDataRefExtension(&e, test.dataref)
+
+		// Make sure adding it passed/fails appropriately
+		if test.pass && err != nil {
+			t.Fatalf("Failed to add DataRefExtension with valid URL(%s): %s",
+				test.dataref, err)
+		}
+		if !test.pass && err == nil {
+			t.Fatalf("Expected not to find DataRefExtension (%s), but did",
+				test.dataref)
+		}
+
+		// Now make sure it's actually there in the 'pass' cases, but
+		// missing in the failed cases.
+		dr, ok := GetDataRefExtension(e)
+		if test.pass {
+			if !ok || dr.DataRef == "" {
+				t.Fatalf("Dataref (%s) is missing after being set",
+					test.dataref)
+			}
+			if dr.DataRef != test.dataref {
+				t.Fatalf("Retrieved dataref(%v) doesn't match set value(%s)",
+					dr, test.dataref)
+			}
+		} else {
+			if ok || dr.DataRef != "" {
+				t.Fatalf("Expected not to find DataRefExtension, but did(%s)",
+					test.dataref)
+			}
+		}
+	}
+}
+
+func TestGetDataRefExtensionNotFound(t *testing.T) {
+	e := event.New()
+
+	// Make sure there's no dataref by default
+	dr, ok := GetDataRefExtension(e)
+	if ok || dr.DataRef != "" {
+		t.Fatal("Expected not to find DataRefExtension, but did")
+	}
+}