Fixed bug in runtime.SetMultipartFormData (Azure#19302)

Slices of io.ReadSeekCloser was improperly handled.

Author: jhendrixMSFT

sdk/azcore/CHANGELOG.md

@@ -7,6 +7,7 @@
 ### Breaking Changes
 
 ### Bugs Fixed
+* Fixed an issue in `runtime.SetMultipartFormData` to properly handle slices of `io.ReadSeekCloser`.
 
 ### Other Changes
 

sdk/azcore/runtime/request.go

@@ -119,16 +119,30 @@ func MarshalAsXML(req *policy.Request, v interface{}) error {
 func SetMultipartFormData(req *policy.Request, formData map[string]interface{}) error {
 	body := bytes.Buffer{}
 	writer := multipart.NewWriter(&body)
+
+	writeContent := func(fieldname, filename string, src io.Reader) error {
+		fd, err := writer.CreateFormFile(fieldname, filename)
+		if err != nil {
+			return err
+		}
+		// copy the data to the form file
+		if _, err = io.Copy(fd, src); err != nil {
+			return err
+		}
+		return nil
+	}
+
 	for k, v := range formData {
 		if rsc, ok := v.(io.ReadSeekCloser); ok {
-			// this is the body to upload, the key is its file name
-			fd, err := writer.CreateFormFile(k, k)
-			if err != nil {
+			if err := writeContent(k, k, rsc); err != nil {
 				return err
 			}
-			// copy the data to the form file
-			if _, err = io.Copy(fd, rsc); err != nil {
-				return err
+			continue
+		} else if rscs, ok := v.([]io.ReadSeekCloser); ok {
+			for _, rsc := range rscs {
+				if err := writeContent(k, k, rsc); err != nil {
+					return err
+				}
 			}
 			continue
 		}

sdk/azcore/runtime/request_test.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/exported"
 	"github.com/Azure/azure-sdk-for-go/sdk/azcore/internal/shared"
+	"github.com/stretchr/testify/require"
 )
 
 type testJSON struct {
@@ -635,6 +636,11 @@ func TestSetMultipartFormData(t *testing.T) {
 		"string": "value",
 		"int":    1,
 		"data":   exported.NopCloser(strings.NewReader("some data")),
+		"datum": []io.ReadSeekCloser{
+			exported.NopCloser(strings.NewReader("first part")),
+			exported.NopCloser(strings.NewReader("second part")),
+			exported.NopCloser(strings.NewReader("third part")),
+		},
 	})
 	if err != nil {
 		t.Fatal(err)
@@ -647,6 +653,7 @@ func TestSetMultipartFormData(t *testing.T) {
 		t.Fatalf("unexpected media type %s", mt)
 	}
 	reader := multipart.NewReader(req.Raw().Body, params["boundary"])
+	var datum []io.ReadSeekCloser
 	for {
 		part, err := reader.NextPart()
 		if err == io.EOF {
@@ -682,8 +689,22 @@ func TestSetMultipartFormData(t *testing.T) {
 			if tr := string(dataPart[:9]); tr != "some data" {
 				t.Fatalf("unexpected value %s", tr)
 			}
+		case "datum":
+			content, err := io.ReadAll(part)
+			require.NoError(t, err)
+			datum = append(datum, exported.NopCloser(bytes.NewReader(content)))
 		default:
 			t.Fatalf("unexpected part %s", fn)
 		}
 	}
+	require.Len(t, datum, 3)
+	first, err := io.ReadAll(datum[0])
+	require.NoError(t, err)
+	second, err := io.ReadAll(datum[1])
+	require.NoError(t, err)
+	third, err := io.ReadAll(datum[2])
+	require.NoError(t, err)
+	require.Equal(t, "first part", string(first))
+	require.Equal(t, "second part", string(second))
+	require.Equal(t, "third part", string(third))
 }