feat(storage): add set_metadata sample (#1858)

* feat(storage): add set_metadata sample

* subtest in a test

* Update storage/objects/set_metadata.go

Co-authored-by: Chris Cotter <cjcotter@google.com>

Co-authored-by: Frank Natividad <frankyn@users.noreply.github.com>
Co-authored-by: Chris Cotter <cjcotter@google.com>

storage/objects/objects_test.go

@@ -171,6 +171,21 @@ func TestObjects(t *testing.T) {
 		t.Errorf("contents = %q; want %q", got, want)
 	}
 
+	t.Run("setMetadata", func(t *testing.T) {
+		bkt := client.Bucket(bucket)
+		obj := bkt.Object(object1)
+		err = setMetadata(ioutil.Discard, bucket, object1)
+		if err != nil {
+			t.Errorf("setMetadata: %v", err)
+		}
+		attrs, err := obj.Attrs(ctx)
+		if err != nil {
+			t.Errorf("object.Attrs: %v", err)
+		}
+		if got, want := attrs.Metadata["keyToAddOrUpdate"], "value"; got != want {
+			t.Errorf("object content = %q; want %q", got, want)
+		}
+	})
 	_, err = getMetadata(ioutil.Discard, bucket, object1)
 	if err != nil {
 		t.Errorf("getMetadata: %v", err)

storage/objects/set_metadata.go

@@ -0,0 +1,54 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package objects
+
+// [START storage_set_metadata]
+import (
+	"context"
+	"fmt"
+	"io"
+	"time"
+
+	"cloud.google.com/go/storage"
+)
+
+// setMetadata sets an object's metadata.
+func setMetadata(w io.Writer, bucket, object string) error {
+	// bucket := "bucket-name"
+	// object := "object-name"
+	ctx := context.Background()
+	client, err := storage.NewClient(ctx)
+	if err != nil {
+		return fmt.Errorf("storage.NewClient: %v", err)
+	}
+	defer client.Close()
+
+	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
+	defer cancel()
+
+	o := client.Bucket(bucket).Object(object)
+	objectAttrsToUpdate := storage.ObjectAttrsToUpdate{
+		Metadata: map[string]string{
+			"keyToAddOrUpdate": "value",
+		},
+	}
+	if _, err := o.Update(ctx, objectAttrsToUpdate); err != nil {
+		return fmt.Errorf("ObjectHandle(%q).Update: %v", object, err)
+	}
+	fmt.Fprintf(w, "Updated custom metadata for object %v in bucket %v.\n", object, bucket)
+	return nil
+}
+
+// [END storage_set_metadata]