labstack
Breaking Change on v4.12.0 When Binding to map[string]interface{} -> the field become list
Issue Description
Breaking change on v4.12.0:
The c.Bind is now mapping query params & request body to list of string.
Example:
POST /test?query=param
request body
{"field1": "somevalue"}
The code
request := make(map[string]interface{})
if err := c.Bind(&request); err != nil {
return err
}
fmt.Printf("%#v", request)
Previous behaviour (pre v4.12.0):
Result: map[string]interface {}{"query":"param", "field1":"somevalue"}
Current behaviour (v4.12.0):
Result: map[string]interface {}{"query":[]string{"param"}, "field1":[]string{"somevalue"}}
Checklist
- [ ] Dependencies installed
- [ ] No typos
- [ ] Searched existing issues and docs
Expected behaviour
The behaviour from the code above should keep on returning non-breaking change and still return this on the newest version:
Result: map[string]interface {}{"query":"param", "field1":"somevalue"}
Actual behaviour
In v4.12.0, the result from the code above returned different result:
Result: map[string]interface {}{"query":[]string{"param"}, "field1":[]string{"somevalue"}}
Steps to reproduce
Working code to debug
package main
func main() {
}
Version/commit
v4.12.0
@slzhffktm I've submitted a pull request (https://github.com/labstack/echo/pull/2656) that addresses this issue by maintaining backwards compatibility for map[string]interface{} binding while supporting the new functionality.
The PR modifies the bindData function to:
- Store single values as strings
- Store multiple values as
[]string
However, if the maintainers decide not to merge this change, here's an alternative solution you can use in your code to achieve the same result:
func ConvertToSingleValues(input map[string]interface{}) map[string]interface{} {
for key, value := range input {
if strSlice, ok := value.([]string); ok {
if len(strSlice) == 1 {
input[key] = strSlice[0]
}
}
}
return input
}
func ExampleFunction(c echo.Context) error {
request := make(map[string]interface{})
if err := c.Bind(&request); err != nil {
return err
}
request := ConvertToSingleValues(request)
return c.JSON(http.StatusOK, request)
}
You can use this helper function with new version without breaking code regardless of whether the PR is merged. It processes the map[string]interface{} returned by c.Bind() and converts any []string values to single strings if they contain only one element.
Hello @thesaltree ! Seems like your PR is merged, thank you for your contribution!!
However, if the maintainers decide not to merge this change, here's an alternative solution you can use in your code to achieve the same result:
func ConvertToSingleValues(input map[string]interface{}) map[string]interface{} { for key, value := range input { if strSlice, ok := value.([]string); ok { if len(strSlice) == 1 { input[key] = strSlice[0] } } } return input }
Your return header is not necessary because map types are reference types:
func ConvertToSingleValues(input map[string]interface{}) {
for key, value := range input {
if strSlice, ok := value.([]string); ok {
if len(strSlice) == 1 {
input[key] = strSlice[0]
}
}
}
}
I stumbled over this issue because I have the same problem after updating to 4.12. I'm wondering when this fix will be released, so until now I'm relying on this helper function.
