rego.Function runtime extension json ints/floats are strings

[shortwavedave]

Hello, I have a custom rego function that validates json input based on some custom logic. Howeverm the a term which is a json object always converts numbers to strings. I tried changing the Args type to types.A and types.NewObject but still the same result. Does anyone have any advice?

		&rego.Function{
			Name:             "validate_custom",
			Decl:             types.NewFunction(types.Args(types.S, types.S), types.A),
			Memoize:          true,
			Nondeterministic: true,
		},
		func(bctx rego.BuiltinContext, a, b *ast.Term) (*ast.Term, error) {
			var inputData map[string]interface{}
			var schemaData string
			if err := ast.As(a.Value, &inputData); err != nil {
				fmt.Printf("Failed to parse inputData: %v\n", err)
				return nil, err
			} else if err := ast.As(b.Value, &schemaData); err != nil {
				fmt.Printf("Failed to parse schemaData: %v\n", err)
				return nil, err
			}

for example, an input like this would erroneously convert the number to a string:

{
"an_integer": 0
}

looks like this when I step through and debug:

{
"an_integer": "0"
}

[johanfylling]

ast.As() and its various sibling functions (e.g. ast.JSON(), ast.ValueToInterface()) will return numbers typed as json.Number, which has string as its base type. Either you can convert these to an appropriate number via an appropriate conversion function provided by json.Number (e.g. json.Number("1").Int64()) as you come across them; or, if this doesn't fit with how you're processing your input and you need to do it all upfront, you could do a json round-trip:

j, err := ast.JSON(operands[0].Value)
if err != nil {
	...
}

bytes, err := json.Marshal(j)
if err != nil {
	...
}

var inputData map[string]interface{}
if err := json.Unmarshal(bytes, &inputData); err != nil {
	..
}

Can't claim that's very pretty, though 😅.