return context error if the context was canceled mid-way

fixes minio#1850

api-list.go

@@ -114,6 +114,7 @@ func (c *Client) listObjectsV2(ctx context.Context, bucketName string, opts List
 			// If contents are available loop through and send over channel.
 			for _, object := range result.Contents {
 				object.ETag = trimEtag(object.ETag)
+				object.Err = ctx.Err()
 				select {
 				// Send object content.
 				case objectStatCh <- object:
@@ -128,7 +129,7 @@ func (c *Client) listObjectsV2(ctx context.Context, bucketName string, opts List
 			for _, obj := range result.CommonPrefixes {
 				select {
 				// Send object prefixes.
-				case objectStatCh <- ObjectInfo{Key: obj.Prefix}:
+				case objectStatCh <- ObjectInfo{Key: obj.Prefix, Err: ctx.Err()}:
 				// If receives done from the caller, return here.
 				case <-ctx.Done():
 					return
@@ -268,6 +269,16 @@ func (c *Client) listObjectsV2Query(ctx context.Context, bucketName, objectPrefi
 	return listBucketResult, nil
 }
 
+// contextCanceled returns whether a context is canceled.
+func contextCanceled(ctx context.Context) bool {
+	select {
+	case <-ctx.Done():
+		return true
+	default:
+		return false
+	}
+}
+
 func (c *Client) listObjects(ctx context.Context, bucketName string, opts ListObjectsOptions) <-chan ObjectInfo {
 	// Allocate new list objects channel.
 	objectStatCh := make(chan ObjectInfo, 1)
@@ -321,6 +332,8 @@ func (c *Client) listObjects(ctx context.Context, bucketName string, opts ListOb
 			for _, object := range result.Contents {
 				// Save the marker.
 				marker = object.Key
+				object.ETag = trimEtag(object.ETag)
+				object.Err = ctx.Err()
 				select {
 				// Send object content.
 				case objectStatCh <- object:
@@ -335,7 +348,7 @@ func (c *Client) listObjects(ctx context.Context, bucketName string, opts ListOb
 			for _, obj := range result.CommonPrefixes {
 				select {
 				// Send object prefixes.
-				case objectStatCh <- ObjectInfo{Key: obj.Prefix}:
+				case objectStatCh <- ObjectInfo{Key: obj.Prefix, Err: ctx.Err()}:
 				// If receives done from the caller, return here.
 				case <-ctx.Done():
 					return
@@ -424,6 +437,7 @@ func (c *Client) listObjectVersions(ctx context.Context, bucketName string, opts
 					IsDeleteMarker: version.isDeleteMarker,
 					UserTags:       version.UserTags,
 					UserMetadata:   version.UserMetadata,
+					Err:            ctx.Err(),
 				}
 				select {
 				// Send object version info.
@@ -439,7 +453,7 @@ func (c *Client) listObjectVersions(ctx context.Context, bucketName string, opts
 			for _, obj := range result.CommonPrefixes {
 				select {
 				// Send object prefixes.
-				case resultCh <- ObjectInfo{Key: obj.Prefix}:
+				case resultCh <- ObjectInfo{Key: obj.Prefix, Err: ctx.Err()}:
 				// If receives done from the caller, return here.
 				case <-ctx.Done():
 					return
@@ -783,6 +797,7 @@ func (c *Client) listIncompleteUploads(ctx context.Context, bucketName, objectPr
 
 			// Send all multipart uploads.
 			for _, obj := range result.Uploads {
+				obj.Err = ctx.Err()
 				// Calculate total size of the uploaded parts if 'aggregateSize' is enabled.
 				select {
 				// Send individual uploads here.
@@ -797,7 +812,7 @@ func (c *Client) listIncompleteUploads(ctx context.Context, bucketName, objectPr
 			for _, obj := range result.CommonPrefixes {
 				select {
 				// Send delimited prefixes here.
-				case objectMultipartStatCh <- ObjectMultipartInfo{Key: obj.Prefix, Size: 0}:
+				case objectMultipartStatCh <- ObjectMultipartInfo{Key: obj.Prefix, Size: 0, Err: ctx.Err()}:
 				// If context is canceled.
 				case <-ctx.Done():
 					return