rest-json: updates rest-json error code retriever util

aws/protocol/restjson/decoder_util.go

@@ -2,68 +2,48 @@ package restjson
 
 import (
 	"encoding/json"
-	"fmt"
 	"io"
 	"strings"
 
 	"github.com/awslabs/smithy-go"
-	smithyjson "github.com/awslabs/smithy-go/json"
 )
 
 // GetErrorInfo util looks for code, __type, and message members in the
 // json body. These members are optionally available, and the function
 // returns the value of member if it is available. This function is useful to
 // identify the error code, msg in a REST JSON error response.
 func GetErrorInfo(decoder *json.Decoder) (errorType string, message string, err error) {
-	startToken, err := decoder.Token()
-	if err == io.EOF {
-		return "", "", nil
+	var errInfo struct {
+		Code    string `json:"code"`
+		Type  string `json:"__type"`
+		Message string `json:"message"`
 	}
-	if err != nil {
-		return "", "", err
-	}
-
-	if t, ok := startToken.(json.Delim); !ok || t.String() != "{" {
-		return "", "", fmt.Errorf("expected start token to be {")
-	}
-
-	for decoder.More() {
-		var target *string
-		t, err := decoder.Token()
-		if err != nil {
-			return "", "", err
-		}
 
-		switch st := t.(string); {
-		case strings.EqualFold(st, "code"):
-			fallthrough
-		case strings.EqualFold(st, "__type"):
-			target = &errorType
-		case strings.EqualFold(st, "message"):
-			target = &message
-		default:
-			smithyjson.DiscardUnknownField(decoder)
-			continue
-		}
-
-		v, err := decoder.Token()
-		if err != nil {
-			return errorType, message, err
+	err = decoder.Decode(&errInfo)
+	if err != nil {
+		if err == io.EOF {
+			return errorType, message, nil
 		}
-		*target = v.(string)
+		return errorType, message, err
 	}
 
-	endToken, err := decoder.Token()
-	if err != nil {
-		return "", "", err
+	// assign error type
+	if len(errInfo.Code) != 0 {
+		errorType = errInfo.Code
+	} else if len(errInfo.Type) != 0 {
+		errorType = errInfo.Type
 	}
 
-	if t, ok := endToken.(json.Delim); !ok || t.String() != "}" {
-		return "", "", fmt.Errorf("expected end token to be }")
+	// assign error message
+	if len(errInfo.Message) != 0 {
+		message = errInfo.Message
 	}
 
 	// sanitize error
-	errorType = SanitizeErrorCode(errorType)
+	if len(errorType) != 0 {
+		errorType = SanitizeErrorCode(errorType)
+	}
+
 	return errorType, message, nil
 }
 

aws/protocol/restjson/decoder_util_test.go

@@ -0,0 +1,77 @@
+package restjson
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestGetErrorInfo(t *testing.T) {
+	cases := map[string]struct {
+		errorResponse                []byte
+		expectedErrorType            string
+		expectedErrorMsg             string
+		expectedDeserializationError string
+	}{
+		"error with code": {
+			errorResponse:     []byte(`{"code": "errorCode", "message": "message for errorCode"}`),
+			expectedErrorType: "errorCode",
+			expectedErrorMsg:  "message for errorCode",
+		},
+		"error with type": {
+			errorResponse:     []byte(`{"__type": "errorCode", "message": "message for errorCode"}`),
+			expectedErrorType: "errorCode",
+			expectedErrorMsg:  "message for errorCode",
+		},
+
+		"error with only message": {
+			errorResponse:    []byte(`{"message": "message for errorCode"}`),
+			expectedErrorMsg: "message for errorCode",
+		},
+
+		"error with only code": {
+			errorResponse:     []byte(`{"code": "errorCode"}`),
+			expectedErrorType: "errorCode",
+		},
+
+		"empty": {
+			errorResponse: []byte(``),
+		},
+
+		"unknownField": {
+			errorResponse:     []byte(`{"xyz":"abc", "code": "errorCode"}`),
+			expectedErrorType: "errorCode",
+		},
+
+		"unexpectedEOF": {
+			errorResponse:                []byte(`{"xyz":"abc"`),
+			expectedDeserializationError: io.ErrUnexpectedEOF.Error(),
+		},
+	}
+
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			decoder := json.NewDecoder(bytes.NewReader(c.errorResponse))
+			actualType, actualMsg, err := GetErrorInfo(decoder)
+			if err != nil {
+				if len(c.expectedDeserializationError) == 0 {
+					t.Fatalf("expected no error, got %v", err.Error())
+				}
+
+				if e, a := c.expectedDeserializationError, err.Error(); !strings.Contains(a, e) {
+					t.Fatalf("expected error to be %v, got %v", e, a)
+				}
+			}
+
+			if e, a := c.expectedErrorType, actualType; !strings.EqualFold(e, a) {
+				t.Fatalf("expected error type to be %v, got %v", e, a)
+			}
+
+			if e, a := c.expectedErrorMsg, actualMsg; !strings.EqualFold(e, a) {
+				t.Fatalf("expected error message to be %v, got %v", e, a)
+			}
+		})
+	}
+}