[s3] Fix a bug in CopyObject and improve Metadata handling

.bazelrc

@@ -1,3 +1,3 @@
 common --enable_bzlmod
 common --experimental_output_paths=strip
-
+common --test_output=errors

services/s3/handler.go

@@ -4,6 +4,7 @@ import (
 	"encoding/xml"
 	"io"
 	"log/slog"
+	"mime"
 	"net/http"
 	"os"
 	"reflect"
@@ -145,11 +146,24 @@ func NewHandler(logger *slog.Logger, s3 *S3) func(w http.ResponseWriter, r *http
 	}
 }
 
+func isASCII(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] >= 128 {
+			return false
+		}
+	}
+	return true
+}
+
 func extractMetadata(header http.Header) map[string]string {
 	metadata := make(map[string]string)
 	for k := range header {
 		if strings.HasPrefix(strings.ToLower(k), "x-amz-meta-") {
-			metadata[k] = header.Get(k)
+			v := header.Get(k)
+			if !isASCII(v) {
+				v = mime.BEncoding.Encode("utf-8", v)
+			}
+			metadata[k] = v
 		}
 	}
 	return metadata

services/s3/itest/BUILD.bazel

@@ -2,7 +2,11 @@ load("@rules_go//go:def.bzl", "go_test")
 
 go_test(
     name = "itest_test",
-    srcs = ["s3_test.go"],
+    srcs = [
+        "copy_object_test.go",
+        "get_object_test.go",
+        "s3_test.go",
+    ],
     deps = [
         "//server",
         "//services/s3",

services/s3/itest/copy_object_test.go

@@ -0,0 +1,35 @@
+package itest
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+)
+
+func TestCopyObject(t *testing.T) {
+	ctx := context.Background()
+	client, srv := makeClientServerPair()
+	defer srv.Shutdown(ctx)
+
+	key := "test-key"
+	_, err := client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: &bucket,
+		Key:    &key,
+		Body:   strings.NewReader("hello"),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.CopyObject(ctx, &s3.CopyObjectInput{
+		Bucket:     &bucket,
+		Key:        &key,
+		CopySource: aws.String("/" + bucket + "/" + key),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}

services/s3/itest/get_object_test.go

@@ -0,0 +1,50 @@
+package itest
+
+import (
+	"context"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/aws/aws-sdk-go-v2/service/s3"
+)
+
+func TestGetObject_Metadata(t *testing.T) {
+	// See https://docs.aws.amazon.com/AmazonS3/latest/userguide/UsingMetadata.html
+	ctx := context.Background()
+	client, srv := makeClientServerPair()
+	defer srv.Shutdown(ctx)
+
+	key := "test-key"
+	_, err := client.PutObject(ctx, &s3.PutObjectInput{
+		Bucket: &bucket,
+		Key:    &key,
+		Body:   strings.NewReader("hello"),
+		Metadata: map[string]string{
+			"ascii":     "AMAZONS3",
+			"non-ascii": "ÄMÄZÕÑ S3",
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	resp, err := client.GetObject(ctx, &s3.GetObjectInput{
+		Bucket: &bucket,
+		Key:    &key,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := resp.Metadata
+	want := map[string]string{
+		"ascii": "AMAZONS3",
+		// Encoding doesn't match exactly but maybe compatible enough?
+		"non-ascii": "=?utf-8?b?w4RNw4Raw5XDkSBTMw==?=",
+		// "non-ascii": "=?UTF-8?B?w4PChE3Dg8KEWsODwpXDg8KRIFMz?=",
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("Wanted %v, got %v", want, got)
+	}
+}

services/s3/itest/s3_test.go

@@ -8,6 +8,7 @@ import (
 	"log/slog"
 	"net"
 	"net/http"
+	"os"
 	"reflect"
 	"strconv"
 	"strings"
@@ -24,17 +25,22 @@ import (
 var bucket = "test-bucket"
 
 func makeClientServerPair() (*s3.Client, *http.Server) {
+	logger := slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{
+		Level: slog.LevelWarn,
+	}))
+
 	listener, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		panic(err)
 	}
 	impl, err := s3Impl.New(s3Impl.Options{
-		Addr: listener.Addr().String(),
+		Addr:   listener.Addr().String(),
+		Logger: logger,
 	})
 	if err != nil {
 		panic(err)
 	}
-	srv := server.NewWithHandlerChain(s3Impl.NewHandler(slog.Default(), impl))
+	srv := server.NewWithHandlerChain(s3Impl.NewHandler(logger, impl))
 	go srv.Serve(listener)
 
 	client := s3.New(s3.Options{

services/s3/s3.go

@@ -516,11 +516,15 @@ func (s *S3) CopyObject(input CopyObjectInput) (*CopyObjectOutput, *awserrors.Er
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	// "bucket/path/to/key"
+	// "bucket/path/to/key", maybe with leading slash.
 	copySource, err := url.PathUnescape(input.CopySource)
 	if err != nil {
 		return nil, awserrors.XXX_TODO(err.Error())
 	}
+	if copySource[0] == '/' {
+		copySource = copySource[1:]
+	}
+
 	parts := strings.SplitN(copySource, "/", 2)
 	sourceBucket := parts[0]
 	sourceKey := parts[1]