Add error check for structs with duplicated tag names

Closes #6

kbuilder/insert.go

@@ -73,7 +73,10 @@ func (i Insert) BuildQuery(dialect ksql.Dialect) (sqlQuery string, params []inte
 		return "", nil, fmt.Errorf("expected Data attr to be a struct or slice of structs but got: %v", t)
 	}
 
-	info := kstructs.GetTagInfo(t)
+	info, err := kstructs.GetTagInfo(t)
+	if err != nil {
+		return "", nil, err
+	}
 
 	b.WriteString(" (")
 	var escapedNames []string

kbuilder/query.go

@@ -204,7 +204,10 @@ func buildSelectQuery(obj interface{}, dialect ksql.Dialect) (string, error) {
 		return query, nil
 	}
 
-	info := kstructs.GetTagInfo(t)
+	info, err := kstructs.GetTagInfo(t)
+	if err != nil {
+		return "", err
+	}
 
 	var escapedNames []string
 	for i := 0; i < info.NumFields(); i++ {

ksql.go

@@ -185,7 +185,10 @@ func (c DB) Query(
 		slice = slice.Slice(0, 0)
 	}
 
-	info := kstructs.GetTagInfo(structType)
+	info, err := kstructs.GetTagInfo(structType)
+	if err != nil {
+		return err
+	}
 
 	firstToken := strings.ToUpper(getFirstToken(query))
 	if info.IsNestedStruct && firstToken == "SELECT" {
@@ -272,7 +275,10 @@ func (c DB) QueryOne(
 		return fmt.Errorf("ksql: expected to receive a pointer to struct, but got: %T", record)
 	}
 
-	info := kstructs.GetTagInfo(tStruct)
+	info, err := kstructs.GetTagInfo(tStruct)
+	if err != nil {
+		return err
+	}
 
 	firstToken := strings.ToUpper(getFirstToken(query))
 	if info.IsNestedStruct && firstToken == "SELECT" {
@@ -342,7 +348,10 @@ func (c DB) QueryChunks(
 		return err
 	}
 
-	info := kstructs.GetTagInfo(structType)
+	info, err := kstructs.GetTagInfo(structType)
+	if err != nil {
+		return err
+	}
 
 	firstToken := strings.ToUpper(getFirstToken(parser.Query))
 	if info.IsNestedStruct && firstToken == "SELECT" {
@@ -445,7 +454,10 @@ func (c DB) Insert(
 		return fmt.Errorf("ksql: expected a valid pointer to struct as argument but received a nil pointer: %v", record)
 	}
 
-	info := kstructs.GetTagInfo(t.Elem())
+	info, err := kstructs.GetTagInfo(t.Elem())
+	if err != nil {
+		return err
+	}
 
 	query, params, scanValues, err := buildInsertQuery(c.dialect, table.name, t, v, info, record, table.idColumns...)
 	if err != nil {
@@ -676,7 +688,10 @@ func (c DB) Update(
 		}
 		tStruct = t.Elem()
 	}
-	info := kstructs.GetTagInfo(tStruct)
+	info, err := kstructs.GetTagInfo(tStruct)
+	if err != nil {
+		return err
+	}
 
 	query, params, err := buildUpdateQuery(c.dialect, table.name, info, record, table.idColumns...)
 	if err != nil {
@@ -940,14 +955,20 @@ func scanRowsFromType(
 		return fmt.Errorf("ksql: expected record to be a pointer to struct, but got: %T", record)
 	}
 
-	info := kstructs.GetTagInfo(t)
+	info, err := kstructs.GetTagInfo(t)
+	if err != nil {
+		return err
+	}
 
 	var scanArgs []interface{}
 	if info.IsNestedStruct {
 		// This version is positional meaning that it expect the arguments
 		// to follow an specific order. It's ok because we don't allow the
 		// user to type the "SELECT" part of the query for nested kstructs.
-		scanArgs = getScanArgsForNestedStructs(dialect, rows, t, v, info)
+		scanArgs, err = getScanArgsForNestedStructs(dialect, rows, t, v, info)
+		if err != nil {
+			return err
+		}
 	} else {
 		names, err := rows.Columns()
 		if err != nil {
@@ -961,11 +982,15 @@ func scanRowsFromType(
 	return rows.Scan(scanArgs...)
 }
 
-func getScanArgsForNestedStructs(dialect Dialect, rows Rows, t reflect.Type, v reflect.Value, info kstructs.StructInfo) []interface{} {
+func getScanArgsForNestedStructs(dialect Dialect, rows Rows, t reflect.Type, v reflect.Value, info kstructs.StructInfo) ([]interface{}, error) {
 	scanArgs := []interface{}{}
 	for i := 0; i < v.NumField(); i++ {
 		// TODO(vingarcia00): Handle case where type is pointer
-		nestedStructInfo := kstructs.GetTagInfo(t.Field(i).Type)
+		nestedStructInfo, err := kstructs.GetTagInfo(t.Field(i).Type)
+		if err != nil {
+			return nil, err
+		}
+
 		nestedStructValue := v.Field(i)
 		for j := 0; j < nestedStructValue.NumField(); j++ {
 			fieldInfo := nestedStructInfo.ByIndex(j)
@@ -985,7 +1010,7 @@ func getScanArgsForNestedStructs(dialect Dialect, rows Rows, t reflect.Type, v r
 		}
 	}
 
-	return scanArgs
+	return scanArgs, nil
 }
 
 func getScanArgsFromNames(dialect Dialect, names []string, v reflect.Value, info kstructs.StructInfo) []interface{} {
@@ -1127,7 +1152,11 @@ func buildSelectQueryForNestedStructs(
 			)
 		}
 
-		nestedStructInfo := kstructs.GetTagInfo(nestedStructType)
+		nestedStructInfo, err := kstructs.GetTagInfo(nestedStructType)
+		if err != nil {
+			return "", err
+		}
+
 		for j := 0; j < structType.Field(i).Type.NumField(); j++ {
 			fields = append(
 				fields,

kstructs/structs.go

@@ -68,18 +68,22 @@ var tagInfoCache = map[reflect.Type]StructInfo{}
 // In the future we might move this cache inside
 // a struct, but for now this accessor is the one
 // we are using
-func GetTagInfo(key reflect.Type) StructInfo {
+func GetTagInfo(key reflect.Type) (StructInfo, error) {
 	return getCachedTagInfo(tagInfoCache, key)
 }
 
-func getCachedTagInfo(tagInfoCache map[reflect.Type]StructInfo, key reflect.Type) StructInfo {
+func getCachedTagInfo(tagInfoCache map[reflect.Type]StructInfo, key reflect.Type) (StructInfo, error) {
 	if info, found := tagInfoCache[key]; found {
-		return info
+		return info, nil
+	}
+
+	info, err := getTagNames(key)
+	if err != nil {
+		return StructInfo{}, err
 	}
 
-	info := getTagNames(key)
 	tagInfoCache[key] = info
-	return info
+	return info, nil
 }
 
 // StructToMap converts any struct type to a map based on
@@ -103,11 +107,15 @@ func StructToMap(obj interface{}) (map[string]interface{}, error) {
 		return nil, fmt.Errorf("input must be a struct or struct pointer")
 	}
 
-	info := getCachedTagInfo(tagInfoCache, t)
+	info, err := getCachedTagInfo(tagInfoCache, t)
+	if err != nil {
+		return nil, err
+	}
 
 	m := map[string]interface{}{}
 	for i := 0; i < v.NumField(); i++ {
-		if !info.ByIndex(i).Valid {
+		fieldInfo := info.ByIndex(i)
+		if !fieldInfo.Valid {
 			continue
 		}
 
@@ -121,7 +129,7 @@ func StructToMap(obj interface{}) (map[string]interface{}, error) {
 			field = field.Elem()
 		}
 
-		m[info.ByIndex(i).Name] = field.Interface()
+		m[fieldInfo.Name] = field.Interface()
 	}
 
 	return m, nil
@@ -213,7 +221,7 @@ func (p PtrConverter) Convert(destType reflect.Type) (reflect.Value, error) {
 //
 // This should save several calls to `Field(i).Tag.Get("foo")`
 // which improves performance by a lot.
-func getTagNames(t reflect.Type) StructInfo {
+func getTagNames(t reflect.Type) (StructInfo, error) {
 	info := StructInfo{
 		byIndex: map[int]*FieldInfo{},
 		byName:  map[string]*FieldInfo{},
@@ -231,6 +239,13 @@ func getTagNames(t reflect.Type) StructInfo {
 			serializeAsJSON = tags[1] == "json"
 		}
 
+		if _, found := info.byName[name]; found {
+			return StructInfo{}, fmt.Errorf(
+				"struct contains multiple attributes with the same ksql tag name: '%s'",
+				name,
+			)
+		}
+
 		info.add(FieldInfo{
 			Name:            name,
 			Index:           i,
@@ -240,7 +255,7 @@ func getTagNames(t reflect.Type) StructInfo {
 
 	// If there were `ksql` tags present, then we are finished:
 	if len(info.byIndex) > 0 {
-		return info
+		return info, nil
 	}
 
 	// If there are no `ksql` tags in the struct, lets assume
@@ -261,7 +276,7 @@ func getTagNames(t reflect.Type) StructInfo {
 		info.IsNestedStruct = true
 	}
 
-	return info
+	return info, nil
 }
 
 // DecodeAsSliceOfStructs makes several checks

kstructs/structs_test.go

@@ -85,6 +85,20 @@ func TestStructToMap(t *testing.T) {
 			"age_attr":  42,
 		}, m)
 	})
+
+	t.Run("should return error for duplicated ksql tag names", func(t *testing.T) {
+		_, err := StructToMap(struct {
+			Name           string `ksql:"name_attr"`
+			DuplicatedName string `ksql:"name_attr"`
+			Age            int    `ksql:"age_attr"`
+		}{
+			Name:           "fake-name",
+			Age:            42,
+			DuplicatedName: "fake-duplicated-name",
+		})
+
+		assert.NotEqual(t, nil, err)
+	})
 }
 
 func TestFillStructWith(t *testing.T) {

kstructs/testhelpers.go

@@ -34,7 +34,11 @@ func FillStructWith(record interface{}, dbRow map[string]interface{}) error {
 		)
 	}
 
-	info := GetTagInfo(t)
+	info, err := GetTagInfo(t)
+	if err != nil {
+		return err
+	}
+
 	for colName, rawSrc := range dbRow {
 		fieldInfo := info.ByName(colName)
 		if !fieldInfo.Valid {