support for parsing error messages from xml responses (#465)

* support for parsing error messages from xml responses

* fixing the linting

* removed some duplicate code

* fix bug introduced in refactoring

* added XML test and fixed bug it uncovered

autorest/azure/azure.go

@@ -17,6 +17,7 @@ package azure
 //  limitations under the License.
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
@@ -143,7 +144,7 @@ type RequestError struct {
 	autorest.DetailedError
 
 	// The error returned by the Azure service.
-	ServiceError *ServiceError `json:"error"`
+	ServiceError *ServiceError `json:"error" xml:"Error"`
 
 	// The request id (from the x-ms-request-id-header) of the request.
 	RequestID string
@@ -285,26 +286,34 @@ func WithErrorUnlessStatusCode(codes ...int) autorest.RespondDecorator {
 				var e RequestError
 				defer resp.Body.Close()
 
+				encodedAs := autorest.EncodedAsJSON
+				if strings.Contains(resp.Header.Get("Content-Type"), "xml") {
+					encodedAs = autorest.EncodedAsXML
+				}
+
 				// Copy and replace the Body in case it does not contain an error object.
 				// This will leave the Body available to the caller.
-				b, decodeErr := autorest.CopyAndDecode(autorest.EncodedAsJSON, resp.Body, &e)
+				b, decodeErr := autorest.CopyAndDecode(encodedAs, resp.Body, &e)
 				resp.Body = ioutil.NopCloser(&b)
 				if decodeErr != nil {
 					return fmt.Errorf("autorest/azure: error response cannot be parsed: %q error: %v", b.String(), decodeErr)
 				}
 				if e.ServiceError == nil {
 					// Check if error is unwrapped ServiceError
-					if err := json.Unmarshal(b.Bytes(), &e.ServiceError); err != nil {
+					decoder := autorest.NewDecoder(encodedAs, bytes.NewReader(b.Bytes()))
+					if err := decoder.Decode(&e.ServiceError); err != nil {
 						return err
 					}
 				}
 				if e.ServiceError.Message == "" {
 					// if we're here it means the returned error wasn't OData v4 compliant.
-					// try to unmarshal the body as raw JSON in hopes of getting something.
+					// try to unmarshal the body in hopes of getting something.
 					rawBody := map[string]interface{}{}
-					if err := json.Unmarshal(b.Bytes(), &rawBody); err != nil {
+					decoder := autorest.NewDecoder(encodedAs, bytes.NewReader(b.Bytes()))
+					if err := decoder.Decode(&rawBody); err != nil {
 						return err
 					}
+
 					e.ServiceError = &ServiceError{
 						Code:    "Unknown",
 						Message: "Unknown service error",

autorest/azure/azure_test.go

@@ -599,6 +599,35 @@ func TestParseResourceID_WithMalformedResourceID(t *testing.T) {
 	}
 }
 
+func TestRequestErrorString_WithXMLError(t *testing.T) {
+	j := `<?xml version="1.0" encoding="utf-8"?>  
+	<Error>  
+	  <Code>InternalError</Code>  
+	  <Message>Internal service error.</Message>  
+	</Error> `
+	uuid := "71FDB9F4-5E49-4C12-B266-DE7B4FD999A6"
+	r := mocks.NewResponseWithContent(j)
+	mocks.SetResponseHeader(r, HeaderRequestID, uuid)
+	r.Request = mocks.NewRequest()
+	r.StatusCode = http.StatusInternalServerError
+	r.Status = http.StatusText(r.StatusCode)
+	r.Header.Add("Content-Type", "text/xml")
+
+	err := autorest.Respond(r,
+		WithErrorUnlessStatusCode(http.StatusOK),
+		autorest.ByClosing())
+
+	if err == nil {
+		t.Fatalf("azure: returned nil error for proper error response")
+	}
+	azErr, _ := err.(*RequestError)
+	const expected = `autorest/azure: Service returned an error. Status=500 Code="InternalError" Message="Internal service error."`
+	if got := azErr.Error(); expected != got {
+		fmt.Println(got)
+		t.Fatalf("azure: send wrong RequestError.\nexpected=%v\ngot=%v", expected, got)
+	}
+}
+
 func withErrorPrepareDecorator(e *error) autorest.PrepareDecorator {
 	return func(p autorest.Preparer) autorest.Preparer {
 		return autorest.PreparerFunc(func(r *http.Request) (*http.Request, error) {

autorest/azure/rp.go

@@ -47,11 +47,15 @@ func DoRetryWithRegistration(client autorest.Client) autorest.SendDecorator {
 				if resp.StatusCode != http.StatusConflict || client.SkipResourceProviderRegistration {
 					return resp, err
 				}
+
 				var re RequestError
-				err = autorest.Respond(
-					resp,
-					autorest.ByUnmarshallingJSON(&re),
-				)
+				if strings.Contains(r.Header.Get("Content-Type"), "xml") {
+					// XML errors (e.g. Storage Data Plane) only return the inner object
+					err = autorest.Respond(resp, autorest.ByUnmarshallingXML(&re.ServiceError))
+				} else {
+					err = autorest.Respond(resp, autorest.ByUnmarshallingJSON(&re))
+				}
+
 				if err != nil {
 					return resp, err
 				}