fix: commonPrefixes behavior in ListObjectVersions (#10286)

```
$ aws s3api --profile minio --endpoint-url http://localhost:9003 \
    list-object-versions --bucket testbucket \
    --delimiter / --prefix Veeam/Archive/

{
    "CommonPrefixes": [
        {
            "Prefix": "Veeam/Archive/003/"
        }
    ]
}
```

Also add coverage tests similar to ListObjects to
catch errors in future, skip these tests in FS mode

cmd/object-api-listobjects_test.go

@@ -405,7 +405,7 @@ func testListObjects(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
 			Prefixes: []string{"newzen/"},
 		},
 		// ListObjectsResult-29.
-		// Marker is set to "Asia/India/Karnataka/Bangalore/Koramangala/pics" in the testCase and delimeter set, (testCase 61).
+		// Marker is set to "Asia/India/Karnataka/Bangalore/Koramangala/pics" in the testCase and delimiter set, (testCase 61).
 		{
 			IsTruncated: false,
 			Objects: []ObjectInfo{
@@ -462,7 +462,7 @@ func testListObjects(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
 		bucketName string
 		prefix     string
 		marker     string
-		delimeter  string
+		delimiter  string
 		maxKeys    int32
 		// Expected output of ListObjects.
 		result ListObjectsInfo
@@ -552,7 +552,7 @@ func testListObjects(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
 		{"test-bucket-list-object", "Asia/India/", "", "", 10, resultCases[23], nil, true},
 		{"test-bucket-list-object", "Asia", "", "", 10, resultCases[24], nil, true},
 		// Tests with prefix and delimiter (55-57).
-		// With delimeter the code should not recurse into the sub-directories of prefix Dir.
+		// With delimiter the code should not recurse into the sub-directories of prefix Dir.
 		{"test-bucket-list-object", "Asia", "", SlashSeparator, 10, resultCases[25], nil, true},
 		{"test-bucket-list-object", "new", "", SlashSeparator, 10, resultCases[26], nil, true},
 		{"test-bucket-list-object", "Asia/India/", "", SlashSeparator, 10, resultCases[27], nil, true},
@@ -579,7 +579,7 @@ func testListObjects(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
 		testCase := testCase
 		t.Run(fmt.Sprintf("%s-Test%d", instanceType, i+1), func(t *testing.T) {
 			result, err := obj.ListObjects(context.Background(), testCase.bucketName,
-				testCase.prefix, testCase.marker, testCase.delimeter, int(testCase.maxKeys))
+				testCase.prefix, testCase.marker, testCase.delimiter, int(testCase.maxKeys))
 			if err != nil && testCase.shouldPass {
 				t.Errorf("Test %d: %s:  Expected to pass, but failed with: <ERROR> %s", i+1, instanceType, err.Error())
 			}
@@ -640,7 +640,632 @@ func testListObjects(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
 			// Take ListObject treeWalk go-routine to completion, if available in the treewalk pool.
 			if result.IsTruncated {
 				_, err = obj.ListObjects(context.Background(), testCase.bucketName,
-					testCase.prefix, result.NextMarker, testCase.delimeter, 1000)
+					testCase.prefix, result.NextMarker, testCase.delimiter, 1000)
+				if err != nil {
+					t.Fatal(err)
+				}
+			}
+		})
+	}
+}
+
+// Wrapper for calling ListObjectVersions tests for both Erasure multiple disks and single node setup.
+func TestListObjectVersions(t *testing.T) {
+	ExecObjectLayerTest(t, testListObjectVersions)
+}
+
+// Unit test for ListObjectVersions
+func testListObjectVersions(obj ObjectLayer, instanceType string, t1 TestErrHandler) {
+	t, _ := t1.(*testing.T)
+	testBuckets := []string{
+		// This bucket is used for testing ListObject operations.
+		"test-bucket-list-object",
+		// This bucket will be tested with empty directories
+		"test-bucket-empty-dir",
+		// Will not store any objects in this bucket,
+		// Its to test ListObjects on an empty bucket.
+		"empty-bucket",
+		// Listing the case where the marker > last object.
+		"test-bucket-single-object",
+	}
+	for _, bucket := range testBuckets {
+		err := obj.MakeBucketWithLocation(context.Background(), bucket, BucketOptions{})
+		if err != nil {
+			t.Fatalf("%s : %s", instanceType, err.Error())
+		}
+	}
+
+	var err error
+	testObjects := []struct {
+		parentBucket string
+		name         string
+		content      string
+		meta         map[string]string
+	}{
+		{testBuckets[0], "Asia-maps.png", "asis-maps", map[string]string{"content-type": "image/png"}},
+		{testBuckets[0], "Asia/India/India-summer-photos-1", "contentstring", nil},
+		{testBuckets[0], "Asia/India/Karnataka/Bangalore/Koramangala/pics", "contentstring", nil},
+		{testBuckets[0], "newPrefix0", "newPrefix0", nil},
+		{testBuckets[0], "newPrefix1", "newPrefix1", nil},
+		{testBuckets[0], "newzen/zen/recurse/again/again/again/pics", "recurse", nil},
+		{testBuckets[0], "obj0", "obj0", nil},
+		{testBuckets[0], "obj1", "obj1", nil},
+		{testBuckets[0], "obj2", "obj2", nil},
+		{testBuckets[1], "obj1", "obj1", nil},
+		{testBuckets[1], "obj2", "obj2", nil},
+		{testBuckets[1], "temporary/0/", "", nil},
+		{testBuckets[3], "A/B", "contentstring", nil},
+	}
+	for _, object := range testObjects {
+		md5Bytes := md5.Sum([]byte(object.content))
+		_, err = obj.PutObject(context.Background(), object.parentBucket, object.name, mustGetPutObjReader(t, bytes.NewBufferString(object.content),
+			int64(len(object.content)), hex.EncodeToString(md5Bytes[:]), ""), ObjectOptions{UserDefined: object.meta})
+		if err != nil {
+			t.Fatalf("%s : %s", instanceType, err.Error())
+		}
+
+	}
+
+	// Formualting the result data set to be expected from ListObjects call inside the tests,
+	// This will be used in testCases and used for asserting the correctness of ListObjects output in the tests.
+
+	resultCases := []ListObjectsInfo{
+		// ListObjectsResult-0.
+		// Testing for listing all objects in the bucket, (testCase 20,21,22).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-1.
+		// Used for asserting the truncated case, (testCase 23).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+			},
+		},
+		// ListObjectsResult-2.
+		// (TestCase 24).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+				{Name: "newPrefix0"},
+			},
+		},
+		// ListObjectsResult-3.
+		// (TestCase 25).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+			},
+		},
+		// ListObjectsResult-4.
+		// Again used for truncated case.
+		// (TestCase 26).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+			},
+		},
+		// ListObjectsResult-5.
+		// Used for Asserting prefixes.
+		// Used for test case with prefix "new", (testCase 27-29).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+			},
+		},
+		// ListObjectsResult-6.
+		// Used for Asserting prefixes.
+		// Used for test case with prefix = "obj", (testCase 30).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-7.
+		// Used for Asserting prefixes and truncation.
+		// Used for test case with prefix = "new" and maxKeys = 1, (testCase 31).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+			},
+		},
+		// ListObjectsResult-8.
+		// Used for Asserting prefixes.
+		// Used for test case with prefix = "obj" and maxKeys = 2, (testCase 32).
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "obj0"},
+				{Name: "obj1"},
+			},
+		},
+		// ListObjectsResult-9.
+		// Used for asserting the case with marker, but without prefix.
+		//marker is set to "newPrefix0" in the testCase, (testCase 33).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-10.
+		//marker is set to "newPrefix1" in the testCase, (testCase 34).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-11.
+		//marker is set to "obj0" in the testCase, (testCase 35).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-12.
+		// Marker is set to "obj1" in the testCase, (testCase 36).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-13.
+		// Marker is set to "man" in the testCase, (testCase37).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-14.
+		// Marker is set to "Abc" in the testCase, (testCase 39).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-15.
+		// Marker is set to "Asia/India/India-summer-photos-1" in the testCase, (testCase 40).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-16.
+		// Marker is set to "Asia/India/Karnataka/Bangalore/Koramangala/pics" in the testCase, (testCase 41).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-17.
+		// Used for asserting the case with marker, without prefix but with truncation.
+		// Marker =  "newPrefix0" & maxKeys = 3 in the testCase, (testCase42).
+		// Output truncated to 3 values.
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+				{Name: "obj0"},
+			},
+		},
+		// ListObjectsResult-18.
+		// Marker = "newPrefix1" & maxkeys = 1 in the testCase, (testCase43).
+		// Output truncated to 1 value.
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+			},
+		},
+		// ListObjectsResult-19.
+		// Marker = "obj0" & maxKeys = 1 in the testCase, (testCase44).
+		// Output truncated to 1 value.
+		{
+			IsTruncated: true,
+			Objects: []ObjectInfo{
+				{Name: "obj1"},
+			},
+		},
+		// ListObjectsResult-20.
+		// Marker = "obj0" & prefix = "obj" in the testCase, (testCase 45).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-21.
+		// Marker = "obj1" & prefix = "obj" in the testCase, (testCase 46).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj2"},
+			},
+		},
+		// ListObjectsResult-22.
+		// Marker = "newPrefix0" & prefix = "new" in the testCase,, (testCase 47).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix1"},
+				{Name: "newzen/zen/recurse/again/again/again/pics"},
+			},
+		},
+		// ListObjectsResult-23.
+		// Prefix is set to "Asia/India/" in the testCase, and delimiter is not set (testCase 55).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+			},
+		},
+
+		// ListObjectsResult-24.
+		// Prefix is set to "Asia" in the testCase, and delimiter is not set (testCase 56).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+				{Name: "Asia/India/India-summer-photos-1"},
+				{Name: "Asia/India/Karnataka/Bangalore/Koramangala/pics"},
+			},
+		},
+
+		// ListObjectsResult-25.
+		// Prefix is set to "Asia" in the testCase, and delimiter is set (testCase 57).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia-maps.png"},
+			},
+			Prefixes: []string{"Asia/"},
+		},
+		// ListObjectsResult-26.
+		// prefix = "new" and delimiter is set in the testCase.(testCase 58).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+			},
+			Prefixes: []string{"newzen/"},
+		},
+		// ListObjectsResult-27.
+		// Prefix is set to "Asia/India/" in the testCase, and delimiter is set to forward slash '/' (testCase 59).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "Asia/India/India-summer-photos-1"},
+			},
+			Prefixes: []string{"Asia/India/Karnataka/"},
+		},
+		// ListObjectsResult-28.
+		// Marker is set to "Asia/India/India-summer-photos-1" and delimiter set in the testCase, (testCase 60).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+			Prefixes: []string{"newzen/"},
+		},
+		// ListObjectsResult-29.
+		// Marker is set to "Asia/India/Karnataka/Bangalore/Koramangala/pics" in the testCase and delimiter set, (testCase 61).
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "newPrefix0"},
+				{Name: "newPrefix1"},
+				{Name: "obj0"},
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+			Prefixes: []string{"newzen/"},
+		},
+		// ListObjectsResult-30.
+		// Prefix and Delimiter is set to '/', (testCase 62).
+		{
+			IsTruncated: false,
+			Objects:     []ObjectInfo{},
+		},
+		// ListObjectsResult-31 Empty directory, recursive listing
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj1"},
+				{Name: "obj2"},
+				{Name: "temporary/0/"},
+			},
+		},
+		// ListObjectsResult-32 Empty directory, non recursive listing
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "obj1"},
+				{Name: "obj2"},
+			},
+			Prefixes: []string{"temporary/"},
+		},
+		// ListObjectsResult-33 Listing empty directory only
+		{
+			IsTruncated: false,
+			Objects: []ObjectInfo{
+				{Name: "temporary/0/"},
+			},
+		},
+		// ListObjectsResult-34:
+		//    * Listing with marker > last object should return empty
+		//    * Listing an object with a trailing slash and '/' delimiter
+		{
+			IsTruncated: false,
+			Objects:     []ObjectInfo{},
+		},
+	}
+
+	testCases := []struct {
+		// Inputs to ListObjects.
+		bucketName string
+		prefix     string
+		marker     string
+		delimiter  string
+		maxKeys    int32
+		// Expected output of ListObjects.
+		result ListObjectsInfo
+		err    error
+		// Flag indicating whether the test is expected to pass or not.
+		shouldPass bool
+	}{
+		// Test cases with invalid bucket names ( Test number 1-4).
+		{".test", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: ".test"}, false},
+		{"Test", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "Test"}, false},
+		{"---", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "---"}, false},
+		{"ad", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "ad"}, false},
+		// Using an existing file for bucket name, but its not a directory (5).
+		{"simple-file.txt", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "simple-file.txt"}, false},
+		// Valid bucket names, but they donot exist (6-8).
+		{"volatile-bucket-1", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "volatile-bucket-1"}, false},
+		{"volatile-bucket-2", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "volatile-bucket-2"}, false},
+		{"volatile-bucket-3", "", "", "", 0, ListObjectsInfo{}, BucketNotFound{Bucket: "volatile-bucket-3"}, false},
+		// Testing for failure cases with both perfix and marker (9).
+		// The prefix and marker combination to be valid it should satisfy strings.HasPrefix(marker, prefix).
+		{"test-bucket-list-object", "asia", "europe-object", "", 0, ListObjectsInfo{}, fmt.Errorf("Invalid combination of marker '%s' and prefix '%s'", "europe-object", "asia"), false},
+		// Setting a non-existing directory to be prefix (10-11).
+		{"empty-bucket", "europe/france/", "", "", 1, ListObjectsInfo{}, nil, true},
+		{"empty-bucket", "africa/tunisia/", "", "", 1, ListObjectsInfo{}, nil, true},
+		// Testing on empty bucket, that is, bucket without any objects in it (12).
+		{"empty-bucket", "", "", "", 0, ListObjectsInfo{}, nil, true},
+		// Setting maxKeys to negative value (13-14).
+		{"empty-bucket", "", "", "", -1, ListObjectsInfo{}, nil, true},
+		{"empty-bucket", "", "", "", 1, ListObjectsInfo{}, nil, true},
+		// Setting maxKeys to a very large value (15).
+		{"empty-bucket", "", "", "", 111100000, ListObjectsInfo{}, nil, true},
+		// Testing for all 10 objects in the bucket (16).
+		{"test-bucket-list-object", "", "", "", 10, resultCases[0], nil, true},
+		//Testing for negative value of maxKey, this should set maxKeys to listObjectsLimit (17).
+		{"test-bucket-list-object", "", "", "", -1, resultCases[0], nil, true},
+		// Testing for very large value of maxKey, this should set maxKeys to listObjectsLimit (18).
+		{"test-bucket-list-object", "", "", "", 1234567890, resultCases[0], nil, true},
+		// Testing for trancated value (19-22).
+		{"test-bucket-list-object", "", "", "", 5, resultCases[1], nil, true},
+		{"test-bucket-list-object", "", "", "", 4, resultCases[2], nil, true},
+		{"test-bucket-list-object", "", "", "", 3, resultCases[3], nil, true},
+		{"test-bucket-list-object", "", "", "", 1, resultCases[4], nil, true},
+		// Testing with prefix (23-26).
+		{"test-bucket-list-object", "new", "", "", 3, resultCases[5], nil, true},
+		{"test-bucket-list-object", "new", "", "", 4, resultCases[5], nil, true},
+		{"test-bucket-list-object", "new", "", "", 5, resultCases[5], nil, true},
+		{"test-bucket-list-object", "obj", "", "", 3, resultCases[6], nil, true},
+		// Testing with prefix and truncation (27-28).
+		{"test-bucket-list-object", "new", "", "", 1, resultCases[7], nil, true},
+		{"test-bucket-list-object", "obj", "", "", 2, resultCases[8], nil, true},
+		// Testing with marker, but without prefix and truncation (29-33).
+		{"test-bucket-list-object", "", "newPrefix0", "", 6, resultCases[9], nil, true},
+		{"test-bucket-list-object", "", "newPrefix1", "", 5, resultCases[10], nil, true},
+		{"test-bucket-list-object", "", "obj0", "", 4, resultCases[11], nil, true},
+		{"test-bucket-list-object", "", "obj1", "", 2, resultCases[12], nil, true},
+		{"test-bucket-list-object", "", "man", "", 11, resultCases[13], nil, true},
+		// Marker being set to a value which is greater than and all object names when sorted (34).
+		// Expected to send an empty response in this case.
+		{"test-bucket-list-object", "", "zen", "", 10, ListObjectsInfo{}, nil, true},
+		// Marker being set to a value which is lesser than and all object names when sorted (35).
+		// Expected to send all the objects in the bucket in this case.
+		{"test-bucket-list-object", "", "Abc", "", 10, resultCases[14], nil, true},
+		// Marker is to a hierarhical value (36-37).
+		{"test-bucket-list-object", "", "Asia/India/India-summer-photos-1", "", 10, resultCases[15], nil, true},
+		{"test-bucket-list-object", "", "Asia/India/Karnataka/Bangalore/Koramangala/pics", "", 10, resultCases[16], nil, true},
+		// Testing with marker and truncation, but no prefix (38-40).
+		{"test-bucket-list-object", "", "newPrefix0", "", 3, resultCases[17], nil, true},
+		{"test-bucket-list-object", "", "newPrefix1", "", 1, resultCases[18], nil, true},
+		{"test-bucket-list-object", "", "obj0", "", 1, resultCases[19], nil, true},
+		// Testing with both marker and prefix, but without truncation (41-43).
+		// The valid combination of marker and prefix should satisfy strings.HasPrefix(marker, prefix).
+		{"test-bucket-list-object", "obj", "obj0", "", 2, resultCases[20], nil, true},
+		{"test-bucket-list-object", "obj", "obj1", "", 1, resultCases[21], nil, true},
+		{"test-bucket-list-object", "new", "newPrefix0", "", 2, resultCases[22], nil, true},
+		// Testing with maxKeys set to 0 (44-50).
+		// The parameters have to valid.
+		{"test-bucket-list-object", "", "obj1", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "", "obj0", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "new", "", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "obj", "", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "obj", "obj0", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "obj", "obj1", "", 0, ListObjectsInfo{}, nil, true},
+		{"test-bucket-list-object", "new", "newPrefix0", "", 0, ListObjectsInfo{}, nil, true},
+		// Tests on hierarchical key names as prefix.
+		// Without delimteter the code should recurse into the prefix Dir.
+		// Tests with prefix, but without delimiter (51-52).
+		{"test-bucket-list-object", "Asia/India/", "", "", 10, resultCases[23], nil, true},
+		{"test-bucket-list-object", "Asia", "", "", 10, resultCases[24], nil, true},
+		// Tests with prefix and delimiter (53-55).
+		// With delimiter the code should not recurse into the sub-directories of prefix Dir.
+		{"test-bucket-list-object", "Asia", "", SlashSeparator, 10, resultCases[25], nil, true},
+		{"test-bucket-list-object", "new", "", SlashSeparator, 10, resultCases[26], nil, true},
+		{"test-bucket-list-object", "Asia/India/", "", SlashSeparator, 10, resultCases[27], nil, true},
+		// Test with marker set as hierarhical value and with delimiter. (56-57)
+		{"test-bucket-list-object", "", "Asia/India/India-summer-photos-1", SlashSeparator, 10, resultCases[28], nil, true},
+		{"test-bucket-list-object", "", "Asia/India/Karnataka/Bangalore/Koramangala/pics", SlashSeparator, 10, resultCases[29], nil, true},
+		// Test with prefix and delimiter set to '/'. (58)
+		{"test-bucket-list-object", SlashSeparator, "", SlashSeparator, 10, resultCases[30], nil, true},
+		// Test with invalid prefix (59)
+		{"test-bucket-list-object", "\\", "", SlashSeparator, 10, ListObjectsInfo{}, nil, true},
+		// Test listing an empty directory in recursive mode (60)
+		{"test-bucket-empty-dir", "", "", "", 10, resultCases[31], nil, true},
+		// Test listing an empty directory in a non recursive mode (61)
+		{"test-bucket-empty-dir", "", "", SlashSeparator, 10, resultCases[32], nil, true},
+		// Test listing a directory which contains an empty directory (62)
+		{"test-bucket-empty-dir", "", "temporary/", "", 10, resultCases[33], nil, true},
+		// Test listing with marker > last object such that response should be empty (63)
+		{"test-bucket-single-object", "", "A/C", "", 1000, resultCases[34], nil, true},
+		// Test listing an object with a trailing slash and a slash delimiter (64)
+		{"test-bucket-list-object", "Asia-maps.png/", "", "/", 1000, resultCases[34], nil, true},
+	}
+
+	for i, testCase := range testCases {
+		testCase := testCase
+		t.Run(fmt.Sprintf("%s-Test%d", instanceType, i+1), func(t *testing.T) {
+			result, err := obj.ListObjectVersions(context.Background(), testCase.bucketName,
+				testCase.prefix, testCase.marker, "", testCase.delimiter, int(testCase.maxKeys))
+			if _, ok := err.(NotImplemented); ok {
+				// Not implemented should be skipped
+				t.Skip()
+			}
+			if err != nil && testCase.shouldPass {
+				t.Errorf("%s:  Expected to pass, but failed with: <ERROR> %s", instanceType, err.Error())
+			}
+			if err == nil && !testCase.shouldPass {
+				t.Errorf("%s: Expected to fail with <ERROR> \"%s\", but passed instead", instanceType, testCase.err.Error())
+			}
+			// Failed as expected, but does it fail for the expected reason.
+			if err != nil && !testCase.shouldPass {
+				if !strings.Contains(err.Error(), testCase.err.Error()) {
+					t.Errorf("%s: Expected to fail with error \"%s\", but instead failed with error \"%s\" instead", instanceType, testCase.err.Error(), err.Error())
+				}
+			}
+			// Since there are cases for which ListObjects fails, this is
+			// necessary. Test passes as expected, but the output values
+			// are verified for correctness here.
+			if err == nil && testCase.shouldPass {
+				// The length of the expected ListObjectsResult.Objects
+				// should match in both expected result from test cases
+				// and in the output. On failure calling t.Fatalf,
+				// otherwise it may lead to index out of range error in
+				// assertion following this.
+				if len(testCase.result.Objects) != len(result.Objects) {
+					t.Fatalf("%s: Expected number of object in the result to be '%d', but found '%d' objects instead", instanceType, len(testCase.result.Objects), len(result.Objects))
+				}
+				for j := 0; j < len(testCase.result.Objects); j++ {
+					if testCase.result.Objects[j].Name != result.Objects[j].Name {
+						t.Errorf("%s: Expected object name to be \"%s\", but found \"%s\" instead", instanceType, testCase.result.Objects[j].Name, result.Objects[j].Name)
+					}
+					// FIXME: we should always check for ETag
+					if result.Objects[j].ETag == "" && !strings.HasSuffix(result.Objects[j].Name, SlashSeparator) {
+						t.Errorf("%s: Expected ETag to be not empty, but found empty instead (%v)", instanceType, result.Objects[j].Name)
+					}
+
+				}
+
+				if len(testCase.result.Prefixes) != len(result.Prefixes) {
+					fmt.Println(testCase, testCase.result.Prefixes, result.Prefixes)
+					t.Fatalf("%s: Expected number of prefixes in the result to be '%d', but found '%d' prefixes instead", instanceType, len(testCase.result.Prefixes), len(result.Prefixes))
+				}
+				for j := 0; j < len(testCase.result.Prefixes); j++ {
+					if testCase.result.Prefixes[j] != result.Prefixes[j] {
+						t.Errorf("%s: Expected prefix name to be \"%s\", but found \"%s\" instead", instanceType, testCase.result.Prefixes[j], result.Prefixes[j])
+					}
+				}
+
+				if testCase.result.IsTruncated != result.IsTruncated {
+					t.Errorf("%s: Expected IsTruncated flag to be %v, but instead found it to be %v", instanceType, testCase.result.IsTruncated, result.IsTruncated)
+				}
+
+				if testCase.result.IsTruncated && result.NextMarker == "" {
+					t.Errorf("%s: Expected NextContinuationToken to contain a string since listing is truncated, but instead found it to be empty", instanceType)
+				}
+
+				if !testCase.result.IsTruncated && result.NextMarker != "" {
+					t.Errorf("%s: Expected NextContinuationToken to be empty since listing is not truncated, but instead found `%v`", instanceType, result.NextMarker)
+				}
+
+			}
+			// Take ListObject treeWalk go-routine to completion, if available in the treewalk pool.
+			if result.IsTruncated {
+				_, err = obj.ListObjectVersions(context.Background(), testCase.bucketName,
+					testCase.prefix, result.NextMarker, "", testCase.delimiter, 1000)
 				if err != nil {
 					t.Fatal(err)
 				}

cmd/xl-storage.go

@@ -873,6 +873,14 @@ func (s *xlStorage) WalkVersions(volume, dirPath, marker string, recursive bool,
 		return nil, err
 	}
 
+	// Fast exit track to check if we are listing an object with
+	// a trailing slash, this will avoid to list the object content.
+	if HasSuffix(dirPath, SlashSeparator) {
+		if st, err := os.Stat(pathJoin(volumeDir, dirPath, xlStorageFormatFile)); err == nil && st.Mode().IsRegular() {
+			return nil, errFileNotFound
+		}
+	}
+
 	// buffer channel matches the S3 ListObjects implementation
 	ch = make(chan FileInfoVersions, maxObjectList)
 	go func() {
@@ -894,6 +902,8 @@ func (s *xlStorage) WalkVersions(volume, dirPath, marker string, recursive bool,
 			var fiv FileInfoVersions
 			if HasSuffix(walkResult.entry, SlashSeparator) {
 				fiv = FileInfoVersions{
+					Volume: volume,
+					Name:   walkResult.entry,
 					Versions: []FileInfo{
 						{
 							Volume: volume,