set stream = ##class(%Stream.FileCharacter).%OpenId("/Users/.../data/continents-en.json")

Did you know that you can just open a file as a stream?

And for iterating - this has been in the product for a while now. This is the code for my :pp alias.

ClassMethod pp(set As %AbstractSet, offset As %Integer = 0)
{
#define QUOTE(%val) $zu(144,1,%val)
    try {
        set isLabeled = set."_isLabeled"()
        if (isLabeled) {
            write "{"
            set close = "}"
        } else {
            write "["
            set close = "]"
        }
        set it = set.iterator()
        while it.hasNext() {
            set next = it.next()
            if $isobject(next.value) {
                write !,?(offset+2)
                write:isLabeled $$$QUOTE(next.key),": "
                do ..pp(next.value, offset + 2)
            } else {
                write !,?(offset+2),$select(isLabeled:$$$QUOTE(next.key)_": ",1:""),$$$QUOTE(next.value)
            }
            if it.hasNext() {
                write ","
            }
        }
        write !,?offset,close
    } catch exc {
        write !,"Exception caught: ",exc.AsSQLMessage()
    }
    return
}

This is in %ASQ.SetUtils. My alias, pp - pretty print, is this:

pp        do ##class(%ASQ.SetUtils).pp($*)

Basically the same as Enrico's:

LATEST:USER>set result = $system.SQL.Execute("select * from %SYS.Namespace_List()")

LATEST:USER>do result.%Display()
Nsp    Status    Remote
%SYS    1    0
B360    1    0
USER    1    0

3 Rows(s) Affected

The PackageDefinition class contains only packages where we need to keep metadata about a package. Most packages do not have any extra metadata.

The SQL solution is the correct solution IMO. If I were a developer on the Object team I would advocate for a method in $system.OBJ - PackageExists(<package_name>) perhaps. :)