[PL-24913]: Handle the error raised while creating a multipart input

scm/driver/stash/integration/git_test.go

@@ -22,6 +22,7 @@ func TestCreateBranch(t *testing.T) {
 		},
 	}
 
+	commitId, _ := GetCurrentCommitOfBranch(client, "master")
 	input := &scm.CreateBranch{
 		Name: "test_branch",
 		Sha:  commitId,

scm/driver/stash/integration/testSettings.go

@@ -14,7 +14,6 @@ var (
 	endpoint = "https://bitbucket.dev.harness.io/"
 	repoID   = "har/scm-integration-test-repo"
 	username = "harnessadmin"
-	commitId = "f675c4b55841908d7c338c500c8f4cb844fd9be7"
 )
 
 func GetCurrentCommitOfBranch(client *scm.Client, branch string) (string, error) {

scm/driver/stash/multipart.go

@@ -0,0 +1,26 @@
+package stash
+
+import "mime/multipart"
+
+type MultipartWriter struct {
+	Writer *multipart.Writer
+	Error  error
+}
+
+func (mw *MultipartWriter) Write(f, v string) {
+	if mw.Error != nil {
+		return
+	}
+	if v == "" {
+		return
+	}
+	mw.Error = mw.Writer.WriteField(f, v)
+}
+
+func (mw *MultipartWriter) Close() {
+	mw.Writer.Close()
+}
+
+func (mw *MultipartWriter) FormDataContentType() string {
+	return mw.Writer.FormDataContentType()
+}

scm/driver/stash/stash.go

@@ -79,26 +79,22 @@ func (c *wrapper) do(ctx context.Context, method, path string, in, out interface
 		case *contentCreateUpdate:
 			// add the content to the multipart
 			var b bytes.Buffer
-			w := multipart.NewWriter(&b)
+			mw := &MultipartWriter{Writer: multipart.NewWriter(&b)}
 			// add the other fields
-			if content.Message != "" {
-				_ = w.WriteField("content", string(content.Content))
+			// The Write function doesn't write the string value to multipart if it is Empty
+			mw.Write("content", string(content.Content))
+			mw.Write("message", content.Message)
+			mw.Write("branch", content.Branch)
+			mw.Write("sourceCommitId", content.Sha)
+			if mw.Error != nil {
+				return nil, fmt.Errorf("error writing multipart-content. err: %s", mw.Error)
 			}
-			if content.Message != "" {
-				_ = w.WriteField("message", content.Message)
-			}
-			if content.Branch != "" {
-				_ = w.WriteField("branch", content.Branch)
-			}
-			if content.Sha != "" {
-				_ = w.WriteField("sourceCommitId", content.Sha)
-			}
-			w.Close()
+			mw.Close()
 			// write the multipart response to the body
 			req.Body = &b
 			// write the content type that contains the length of the multipart
 			req.Header = map[string][]string{
-				"Content-Type": {w.FormDataContentType()},
+				"Content-Type": {mw.FormDataContentType()},
 			}
 		default:
 			buf := new(bytes.Buffer)