value:toJson has not mentioned on how to handle tagged data values

[Nadeeshan96]

Description:

Though value:toJson has mentioned about table and xml type anydata values, it does not mention how to handle tagged data values such as values of type lang.regexp:RegExp.

ballerina-spec/lang/lib/value.bal

Lines 117 to 132 in c88701b

	# Converts a value of type `anydata` to `json`.
	# This does a deep copy of `v` converting values that do
	# not belong to json into values that do.
	# A value of type `xml` is converted into a string as if
	# by the `toString` function.
	# A value of type `table` is converted into a list of
	# mappings one for each row.
	# The inherent type of arrays in the return value will be
	# `json[]` and of mappings will be `map<json>`.
	# A new copy is made of all structural values, including
	# immutable values.
	#
	# + v - anydata value
	# + return - representation of `v` as value of type json
	# This panics if `v` has cycles.
	public isolated function toJson(anydata v) returns json = external;

The spec has defined https://ballerina.io/spec/lang/master/#ToString for tagged data types. Do we need to just call value:toString when value:toJson is called on tagged data values or what should be done here?

Suggested Labels:

spec/undefined

Code sample that shows issue:

import ballerina/lang.regexp;
import ballerina/io;

public function main() {
    regexp:RegExp regExp = re `AB+C*D{1,4}`;
    json jsonVal = regExp.toJson(); 
    io:println(jsonVal);
}

currently gives

Running executable

error: {ballerina/lang.value}ConversionError {"message":"'anydata & readonly' value cannot be converted to 'json'"}
        at ballerina.lang.value.0:toJson(value.bal:262)
           reg:main(reg.bal:6)

Related Issues:

ballerina-platform/ballerina-lang#42070

[jclark]

Tagged data values should be output as strings. The other way round should work too.