"Nullness" of a JSON null is lost while iterating using formap

[tiymat]

Describe the bug:
When iterating over a JSON object using formap, is-null will always report the value as being non-null.

Expected behaviour:
is-null should behave the same whether or not it's invoked on the value of an object in a formap loop.

Screenshots:

~ » %{ "foo": null } -> set x
~ » if { is-null $x['foo'] } then { out "foo is null" } else { out "foo is NOT null" }
foo is null
~ » $x -> formap k v { if { is-null v } then { out "$k is null" } else { out "$k is NOT null" } }
foo is NOT null

Platform (please complete the following information):

• OS, output from uname -a if supported: Ubuntu 23.04
• Terminal Emulator: GNOME Terminal
• Murex version, output from version --no-app-name: 5.3.6000

Additional context:
Can be worked around by disregarding the variable formap uses for the value like so

~ » $x -> formap k v { if { is-null $x[$k] } then { out "$k is null" } else { out "$k is NOT null" } }
foo is null

but I'm not sure if it's safe to access the value in this way while iterating over the object?

[lmorg]

Looks like you've uncovered not one, but two bugs in the parser.

null bareword parsed as string:

» %{ "foo": null }
{
    "foo": "null"
}

variables are tokenised for is-null parameters

» $foo = "bar"
» is-null foo
foo: defined and not null
» is-null $foo
bar: undefined or null

---

Both of these are trivially fixable so I'll get an update pushed to develop shortly

[lmorg]

@tiymat pushed a fix to develop. I'll probably put this live in the next day or two because it's a low impact change.

[tiymat]

In testing the develop version (5.3.7000) I noticed a potentially-related issue.

In JSON objects constructed with %{} syntax, is-null seems to interpret empty strings as nulls, contradicting the documentation which says "Zero length strings [...] are all not null."

tmp » cat test.mx
#!/usr/bin/murex

%{ "foo": "" } -> formap key value {
	if { is-null value } then {
		out "value is null"
	} else {
		out "value is NOT null"
	}
}
tmp » ./test.mx
value is null

Edit: I guess the issue isn't with is-null itself but rather how the JSON object is being parsed/constructed.

~ » %{ "foo": '' }
{
    "foo": null
}

[lmorg]

Good spot.

The parser for object creator was a little slapdash. I'm pretty sure I wrote that code wrapped under a blanket while fighting off covid. Which also explains why the tests aren't thorough enough.

I'm going to merge the changes I have currently and will rewrite the object creator parser for a new release.