test(remote_storage/s3): assert WriteFile success in mime tests

filer.remote.sync was uploading every object without a Content-Type, so
S3-compatible backends (e.g. Backblaze B2) stored binary/octet-stream
and browsers refused to render HTML, CSS, etc.

Pass entry.Attributes.Mime through to UploadInput.ContentType, leaving
the header unset when no Mime is recorded so the remote keeps its own
default behavior.

weed/remote_storage/s3/s3_storage_client.go

@@ -299,6 +299,9 @@ func (s *s3RemoteStorageClient) WriteFile(loc *remote_pb.RemoteStorageLocation,
 		Body:    reader,
 		Tagging: awsTags,
 	}
+	if entry.Attributes != nil && entry.Attributes.Mime != "" {
+		uploadInput.ContentType = aws.String(entry.Attributes.Mime)
+	}
 	if s.conf.S3StorageClass != "" {
 		uploadInput.StorageClass = aws.String(s.conf.S3StorageClass)
 	}

weed/remote_storage/s3/s3_storage_client_test.go

@@ -1,10 +1,15 @@
 package s3
 
 import (
+	"bytes"
+	"io"
+	"net/http"
+	"strings"
 	"testing"
 
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	awss3 "github.com/aws/aws-sdk-go/service/s3"
+	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
 	"github.com/seaweedfs/seaweedfs/weed/pb/remote_pb"
 	"github.com/seaweedfs/seaweedfs/weed/remote_storage"
 	"github.com/stretchr/testify/require"
@@ -65,3 +70,89 @@ func TestS3ErrRemoteObjectNotFoundIsAccessible(t *testing.T) {
 	require.Error(t, remote_storage.ErrRemoteObjectNotFound)
 	require.Equal(t, "remote object not found", remote_storage.ErrRemoteObjectNotFound.Error())
 }
+
+// captureRoundTripper records the PUT request that the s3manager uploader
+// sends, and short-circuits all calls with a 200 so the SDK is satisfied.
+type captureRoundTripper struct {
+	uploadReq *http.Request
+}
+
+func (c *captureRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	if req.Method == http.MethodPut {
+		c.uploadReq = req.Clone(req.Context())
+	}
+	if req.Body != nil {
+		_, _ = io.Copy(io.Discard, req.Body)
+		_ = req.Body.Close()
+	}
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       io.NopCloser(strings.NewReader("")),
+		Header: http.Header{
+			"ETag": []string{"\"etag\""},
+		},
+		Request: req,
+	}, nil
+}
+
+func (c *captureRoundTripper) uploadContentType() string {
+	if c.uploadReq == nil {
+		return ""
+	}
+	return c.uploadReq.Header.Get("Content-Type")
+}
+
+func newCapturingS3Client(t *testing.T) (*s3RemoteStorageClient, *captureRoundTripper) {
+	t.Helper()
+	rt := &captureRoundTripper{}
+	conf := &remote_pb.RemoteConf{
+		Name:             "test",
+		S3Region:         "us-east-1",
+		S3Endpoint:       "https://example.invalid",
+		S3ForcePathStyle: true,
+		S3AccessKey:      "test-key",
+		S3SecretKey:      "test-secret",
+	}
+	httpClient := &http.Client{Transport: rt}
+	rs, err := MakeWithHTTPClient(conf, httpClient)
+	require.NoError(t, err)
+	return rs.(*s3RemoteStorageClient), rt
+}
+
+func TestS3WriteFilePassesMimeAsContentType(t *testing.T) {
+	client, rt := newCapturingS3Client(t)
+	loc := &remote_pb.RemoteStorageLocation{
+		Name:   "test",
+		Bucket: "bucket",
+		Path:   "/dir/test.html",
+	}
+	entry := &filer_pb.Entry{
+		Attributes: &filer_pb.FuseAttributes{Mime: "text/html"},
+	}
+
+	_, err := client.WriteFile(loc, entry, bytes.NewReader([]byte("<html></html>")))
+	require.NoError(t, err)
+
+	require.NotNil(t, rt.uploadReq, "uploader should have issued a PUT")
+	require.Equal(t, "text/html", rt.uploadContentType(), "Content-Type should match entry.Attributes.Mime")
+}
+
+func TestS3WriteFileOmitsContentTypeWhenMimeMissing(t *testing.T) {
+	client, rt := newCapturingS3Client(t)
+	loc := &remote_pb.RemoteStorageLocation{
+		Name:   "test",
+		Bucket: "bucket",
+		Path:   "/dir/test.bin",
+	}
+	entry := &filer_pb.Entry{
+		Attributes: &filer_pb.FuseAttributes{},
+	}
+
+	_, err := client.WriteFile(loc, entry, bytes.NewReader([]byte("data")))
+	require.NoError(t, err)
+
+	require.NotNil(t, rt.uploadReq, "uploader should have issued a PUT")
+	// When entry.Attributes.Mime is empty we don't force a Content-Type so the
+	// remote can apply its own default rather than getting a misleading one.
+	require.Equal(t, "", rt.uploadContentType())
+}