Prevent panic in exported.Payload (#22148)

Treat a nil response body as no body.

sdk/internal/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+* Prevent `exported.Payload` from panicking in the rare event `*http.Response.Body` is `nil`.
+
 ### Other Changes
 
 ## 1.5.1 (2023-12-06)

sdk/internal/exported/exported.go

@@ -39,6 +39,11 @@ type PayloadOptions struct {
 // Subsequent reads will access the cached value.
 // Exported as runtime.Payload() WITHOUT the opts parameter.
 func Payload(resp *http.Response, opts *PayloadOptions) ([]byte, error) {
+	if resp.Body == nil {
+		// this shouldn't happen in real-world scenarios as a
+		// response with no body should set it to http.NoBody
+		return nil, nil
+	}
 	modifyBytes := func(b []byte) []byte { return b }
 	if opts != nil && opts.BytesModifier != nil {
 		modifyBytes = opts.BytesModifier

sdk/internal/exported/exported_test.go

@@ -61,6 +61,12 @@ func TestPayloadBytesModifier(t *testing.T) {
 	require.EqualValues(t, newPayload, string(b))
 }
 
+func TestPayloadNilBody(t *testing.T) {
+	b, err := Payload(&http.Response{}, nil)
+	require.NoError(t, err)
+	require.Nil(t, b)
+}
+
 func TestNopClosingBytesReader(t *testing.T) {
 	const val1 = "the data"
 	ncbr := &nopClosingBytesReader{s: []byte(val1)}