refactor

matchers/have_existing_field_matcher.go

@@ -12,13 +12,19 @@ type HaveExistingFieldMatcher struct {
 }
 
 func (matcher *HaveExistingFieldMatcher) Match(actual interface{}) (success bool, err error) {
+	// we don't care about the field's actual value, just about any error in
+	// trying to find the field (or method).
 	_, err = extractField(actual, matcher.Field, "HaveExistingField")
-	// Report "severe" field extraction errors, but not a missing field.
-	var ferr fieldError
-	if errors.As(err, &ferr) {
-		return false, ferr
+	if err == nil {
+		return true, nil
 	}
-	return err == nil, nil
+	var mferr missingFieldError
+	if errors.As(err, &mferr) {
+		// missing field errors aren't errors in this context, but instead
+		// unsuccessful matches.
+		return false, nil
+	}
+	return false, err
 }
 
 func (matcher *HaveExistingFieldMatcher) FailureMessage(actual interface{}) (message string) {

matchers/have_field.go

@@ -8,12 +8,12 @@ import (
 	"github.com/onsi/gomega/format"
 )
 
-// fieldError represents a "severe" field extraction error that
-// HaveExistingFieldMatcher must not ignore and thus not interpret as simply a
-// missing field.
-type fieldError string
+// missingFieldError represents a missing field extraction error that
+// HaveExistingFieldMatcher can ignore, as opposed to other, sever field
+// extraction errors, such as nil pointers, et cetera.
+type missingFieldError string
 
-func (e fieldError) Error() string {
+func (e missingFieldError) Error() string {
 	return string(e)
 }
 
@@ -25,11 +25,11 @@ func extractField(actual interface{}, field string, matchername string) (interfa
 		actualValue = actualValue.Elem()
 	}
 	if actualValue == (reflect.Value{}) {
-		return nil, fieldError(fmt.Sprintf("%s encountered nil while dereferencing a pointer of type %T.", matchername, actual))
+		return nil, fmt.Errorf("%s encountered nil while dereferencing a pointer of type %T.", matchername, actual)
 	}
 
 	if actualValue.Kind() != reflect.Struct {
-		return nil, fieldError(fmt.Sprintf("%s encountered:\n%s\nWhich is not a struct.", matchername, format.Object(actual, 1)))
+		return nil, fmt.Errorf("%s encountered:\n%s\nWhich is not a struct.", matchername, format.Object(actual, 1))
 	}
 
 	var extractedValue reflect.Value
@@ -40,17 +40,17 @@ func extractField(actual interface{}, field string, matchername string) (interfa
 			extractedValue = actualValue.Addr().MethodByName(strings.TrimSuffix(fields[0], "()"))
 		}
 		if extractedValue == (reflect.Value{}) {
-			return nil, fmt.Errorf("%s could not find method named '%s' in struct of type %T.", matchername, fields[0], actual)
+			return nil, missingFieldError(fmt.Sprintf("%s could not find method named '%s' in struct of type %T.", matchername, fields[0], actual))
 		}
 		t := extractedValue.Type()
 		if t.NumIn() != 0 || t.NumOut() != 1 {
-			return nil, fieldError(fmt.Sprintf("%s found an invalid method named '%s' in struct of type %T.\nMethods must take no arguments and return exactly one value.", matchername, fields[0], actual))
+			return nil, fmt.Errorf("%s found an invalid method named '%s' in struct of type %T.\nMethods must take no arguments and return exactly one value.", matchername, fields[0], actual)
 		}
 		extractedValue = extractedValue.Call([]reflect.Value{})[0]
 	} else {
 		extractedValue = actualValue.FieldByName(fields[0])
 		if extractedValue == (reflect.Value{}) {
-			return nil, fmt.Errorf("%s could not find field named '%s' in struct:\n%s", matchername, fields[0], format.Object(actual, 1))
+			return nil, missingFieldError(fmt.Sprintf("%s could not find field named '%s' in struct:\n%s", matchername, fields[0], format.Object(actual, 1)))
 		}
 	}