Clarify parenthesis errors

filterExprParser.go

@@ -133,8 +133,10 @@ func (f *FilterExpression) outputExpressionNoParenCheck() (Expression, error) {
 
 // Outputs the head of the Expression match tree of which represents everything underneath
 func (f *FilterExpression) OutputExpression() (Expression, error) {
- if f.GetTotalOpenParens() != f.GetTotalCloseParens() {
- return nil, ErrorMalformedParenthesis
+ openParens := f.GetTotalOpenParens()
+ closeParens := f.GetTotalCloseParens()
+ if openParens != closeParens {
+ return nil, fmt.Errorf("%s: found %v open parentheses and %v close parentheses", ErrorMalformedParenthesis, openParens, closeParens)
  }
 
  return f.outputExpressionNoParenCheck()

filterExprParser_test.go

@@ -5,6 +5,7 @@ package gojsonsm
 import (
  "encoding/json"
  "github.com/stretchr/testify/assert"
+ "strings"
  "testing"
 )
 
@@ -674,13 +675,15 @@ func TestFilterExpressionParser(t *testing.T) {
  err = parser.ParseString("(TRUE) OR FALSE)", fe)
  assert.Nil(err)
  expr, err = fe.OutputExpression()
- assert.Equal(ErrorMalformedParenthesis, err)
+ assert.NotNil(err)
+ assert.True(strings.Contains(err.Error(), ErrorMalformedParenthesis.Error()))
 
  fe = &FilterExpression{}
  err = parser.ParseString("(((TRUE) OR FALSE) OR FALSE))", fe)
  assert.Nil(err)
  expr, err = fe.OutputExpression()
- assert.Equal(ErrorMalformedParenthesis, err)
+ assert.NotNil(err)
+ assert.True(strings.Contains(err.Error(), ErrorMalformedParenthesis.Error()))
 
  fe = &FilterExpression{}
  err = parser.ParseString("TRUE", fe)