improve validation error message printing

pkg/api/errors/validation.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/davecgh/go-spew/spew"
 	"github.com/golang/glog"
 )
 
@@ -51,8 +52,8 @@ const (
 	ValidationErrorTypeForbidden ValidationErrorType = "FieldValueForbidden"
 )
 
-// ValueOf converts a ValidationErrorType into its corresponding error message.
-func ValueOf(t ValidationErrorType) string {
+// String converts a ValidationErrorType into its corresponding error message.
+func (t ValidationErrorType) String() string {
 	switch t {
 	case ValidationErrorTypeNotFound:
 		return "not found"
@@ -83,7 +84,7 @@ type ValidationError struct {
 var _ error = &ValidationError{}
 
 func (v *ValidationError) Error() string {
-	s := fmt.Sprintf("%s: %s '%v'", v.Field, ValueOf(v.Type), v.BadValue)
+	s := spew.Sprintf("%s: %s '%+v'", v.Field, v.Type, v.BadValue)
 	if v.Detail != "" {
 		s += fmt.Sprintf(": %s", v.Detail)
 	}

pkg/api/errors/validation_test.go

@@ -56,10 +56,39 @@ func TestMakeFuncs(t *testing.T) {
 	}
 }
 
-func TestValidationError(t *testing.T) {
+func TestValidationErrorUsefulMessage(t *testing.T) {
 	s := NewFieldInvalid("foo", "bar", "deet").Error()
-	if !strings.Contains(s, "foo") || !strings.Contains(s, "bar") || !strings.Contains(s, "deet") || !strings.Contains(s, ValueOf(ValidationErrorTypeInvalid)) {
-		t.Errorf("error message did not contain expected values, got %s", s)
+	t.Logf("message: %v", s)
+	for _, part := range []string{"foo", "bar", "deet", ValidationErrorTypeInvalid.String()} {
+		if !strings.Contains(s, part) {
+			t.Errorf("error message did not contain expected part '%v'", part)
+		}
+	}
+
+	type complicated struct {
+		Baz   int
+		Qux   string
+		Inner interface{}
+		KV    map[string]int
+	}
+	s = NewFieldRequired(
+		"foo",
+		&complicated{
+			Baz:   1,
+			Qux:   "aoeu",
+			Inner: &complicated{Qux: "asdf"},
+			KV:    map[string]int{"Billy": 2},
+		},
+	).Error()
+	t.Logf("message: %v", s)
+	for _, part := range []string{
+		"foo", ValidationErrorTypeRequired.String(),
+		"Baz", "Qux", "Inner", "KV",
+		"1", "aoeu", "asdf", "Billy", "2",
+	} {
+		if !strings.Contains(s, part) {
+			t.Errorf("error message did not contain expected part '%v'", part)
+		}
 	}
 }