feat: add ChecksumType to CompleteMultipartUpload response struct

Signed-off-by: Shooks <justanormalme@gmail.com>

buildscripts/rebrand-guard/compat-baseline.json

@@ -1811,6 +1811,7 @@
     "cmd:cmd:field:CompleteMultipartUploadResponse.ChecksumCRC64NVME",
     "cmd:cmd:field:CompleteMultipartUploadResponse.ChecksumSHA1",
     "cmd:cmd:field:CompleteMultipartUploadResponse.ChecksumSHA256",
+    "cmd:cmd:field:CompleteMultipartUploadResponse.ChecksumType",
     "cmd:cmd:field:CompleteMultipartUploadResponse.ETag",
     "cmd:cmd:field:CompleteMultipartUploadResponse.Key",
     "cmd:cmd:field:CompleteMultipartUploadResponse.Location",

cmd/api-response.go

@@ -416,6 +416,7 @@ type CompleteMultipartUploadResponse struct {
 	Key      string
 	ETag     string
 
+	ChecksumType      string `xml:"ChecksumType,omitempty"`
 	ChecksumCRC32     string `xml:"ChecksumCRC32,omitempty"`
 	ChecksumCRC32C    string `xml:"ChecksumCRC32C,omitempty"`
 	ChecksumSHA1      string `xml:"ChecksumSHA1,omitempty"`
@@ -797,6 +798,7 @@ func generateCompleteMultipartUploadResponse(bucket, key, location string, oi Ob
 		Key:      key,
 		// AWS S3 quotes the ETag in XML, make sure we are compatible here.
 		ETag:              "\"" + oi.ETag + "\"",
+		ChecksumType:      cs[xhttp.AmzChecksumType],
 		ChecksumSHA1:      cs[hash.ChecksumSHA1.String()],
 		ChecksumSHA256:    cs[hash.ChecksumSHA256.String()],
 		ChecksumCRC32:     cs[hash.ChecksumCRC32.String()],

cmd/object-handlers_test.go

@@ -43,6 +43,7 @@ import (
 	"github.com/dustin/go-humanize"
 	"github.com/minio/minio/internal/auth"
 	"github.com/minio/minio/internal/crypto"
+	minhash "github.com/minio/minio/internal/hash"
 	"github.com/minio/minio/internal/hash/sha256"
 	xhttp "github.com/minio/minio/internal/http"
 	ioutilx "github.com/minio/minio/internal/ioutil"
@@ -3386,6 +3387,62 @@ func testAPICompleteMultipartHandler(obj ObjectLayer, instanceType, bucketName s
 	ExecObjectLayerAPINilTest(t, nilBucket, nilObject, instanceType, apiRouter, nilReq)
 }
 
+// TestGenerateCompleteMultipartUploadResponseChecksumType verifies that
+// ChecksumType is populated as FULL_OBJECT/COMPOSITE when the object carries
+// a checksum, and omitted from the XML entirely when it doesn't.
+func TestGenerateCompleteMultipartUploadResponseChecksumType(t *testing.T) {
+	bucket, key := "test-bucket", "test-object"
+
+	testCases := []struct {
+		name             string
+		checksum         *minhash.Checksum
+		wantChecksumType string
+	}{
+		{
+			name:             "no checksum",
+			checksum:         nil,
+			wantChecksumType: "",
+		},
+		{
+			name:             "full object checksum",
+			checksum:         minhash.NewChecksumFromData(minhash.ChecksumCRC32, []byte("full-object-data")),
+			wantChecksumType: xhttp.AmzChecksumTypeFullObject,
+		},
+		{
+			name: "composite multipart checksum",
+			checksum: func() *minhash.Checksum {
+				c := minhash.NewChecksumFromData(minhash.ChecksumCRC32C|minhash.ChecksumMultipart, []byte("combined-part-checksums"))
+				c.WantParts = 2
+				return c
+			}(),
+			wantChecksumType: xhttp.AmzChecksumTypeComposite,
+		},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			oi := ObjectInfo{ETag: "d41d8cd98f00b204e9800998ecf8427e"}
+			if tt.checksum != nil {
+				oi.Checksum = tt.checksum.AppendTo(nil, nil)
+			}
+
+			resp := generateCompleteMultipartUploadResponse(bucket, key, getGetObjectURL("", bucket, key), oi, nil)
+			if resp.ChecksumType != tt.wantChecksumType {
+				t.Fatalf("ChecksumType: got %q, want %q", resp.ChecksumType, tt.wantChecksumType)
+			}
+
+			encoded, err := xml.Marshal(resp)
+			if err != nil {
+				t.Fatalf("failed to marshal response: %v", err)
+			}
+			gotTag := strings.Contains(string(encoded), "<ChecksumType>")
+			if wantTag := tt.wantChecksumType != ""; gotTag != wantTag {
+				t.Fatalf("ChecksumType tag presence: got %v, want %v (xml: %s)", gotTag, wantTag, encoded)
+			}
+		})
+	}
+}
+
 // The UploadID from the response body is parsed and its existence is asserted with an attempt to ListParts using it.
 func TestAPIAbortMultipartHandler(t *testing.T) {
 	defer DetectTestLeak(t)()