Filtering on fields of type dictionary does not work

[torie]

I am trying to filter responses by a specific key-value combination for a dictionary field, which seems to not be working.

Steps to reproduce:

Define a resource with a schema.Field with the following specification:

"foobar": {
        Description: "A set of key values.",
        Validator: &schema.Dict{
	        KeysValidator:   &schema.String{MinLen: 1},
		ValuesValidator: &schema.String{MinLen: 1},
	},
	Filterable: true,
},

Make a request to get resources which has a specific key-value pair in the foobar dictionary.

http://myapi.com/myresource?filter={"foobar":{"foo": "bar"}}

The following error occurs.

"Invalid `filter` parameter: foobar: invalid query expression: not a dict"

---

I've done some digging, and the error occurs in schema/dict.go when the func (v Dict) Validate(...) function attempts to check if the incoming value is of type map[string]interface{}. At this point the value has been parsed into map[string]query.Value which fails the test.

// Validate implements FieldValidator interface.
func (v Dict) Validate(value interface{}) (interface{}, error) {
	dict, ok := value.(map[string]interface{}) // <- value is of type map[string]query.Value here
	if !ok {
		return nil, errors.New("not a dict")
	}
        ...

[smyrman]

For us (me and @torie at Searis), there are actually two cases we would like to work:

• Case 1: exact match http://myapi.com/myresource?filter={"foobar":{"foo": "bar"}}

This is actually not too important.

• Case 2: search for the value of a key http://myapi.com/myresource?filter={"foobar.foo": "bar"}

This is more relevant, as it would allow us to use a dictionary to hold arbitrary tag/label values and filter based on individual fields.

[smyrman]

As for case2, the first step would be to make sure the following code can find the field of a schema.Dict or schema.Object:

rest-layer/schema/schema.go

Line 57 in 5b33327

func (s Schema) GetField(name string) *Field {

Most likely this would involve these two types implementing a GetField method and check for it in a similar way we already do if a field have a Schema.

[smyrman]

Starting on case 2 only for now.

[smyrman]

"Invalid filter parameter: foobar: invalid query expression: not a dict"

This issue is the same for both Dict and Array, and is caused by the parsing to map[string]query.Value and []quey.Value over map[string]interface{} and []interface{}.

rest-layer/schema/query/predicate.go

Line 68 in 14f9636

type Value interface{}

According to @torie, the type does not seam to have any methods or other properties. Replacing it with interface{} in the code, would make the parsing simpler, solve ths bug, and deprecate functions that exist in the code today to translate between query.Value and interface{}. We could also use a go type alias over a declaration, if we want that for clarity.

type Value = interface{}

[smyrman]

PS! This is for the exact match semantics.

[rs]

👌

[smyrman]

This should be completely solved by #177