Initially, the question was asked in relation to Caché or/and Ensemble 2018.1, but not to IRIS.

There are many examples in the documentation: Using Dynamic SQL

$SYSTEM.Process.UserName(##class(%SYS.ProcessQuery).NextProcess(""))

Another solution via $LISTFROMSTRING:

set s="item1"
for i=2:1:5 {
  set s=s_",item"_i
}
set mylist=$listfromstring(s)
zwrite mylist ; mylist = $lb("item1","item2","item3","item4","item5")

USER>w $zv
IRIS for Windows (x86-64) 2024.3 (Build 217U) Thu Nov 14 2024 17:59:58 EST

USER>w $$GetEnvironment^%apiOBJ("collation","%Library.String",.collval),! zw collval
1
 
USER>w $$GetEnvironment^%apiOBJ("collation","dc.Username",.collval),! zw collval
1
 
USER>zn "%SYS"
 
%SYS>w $$GetEnvironment^%apiOBJ("collation","%Library.String",.collval),! zw collval
1
 
%SYS>w $$GetEnvironment^%apiOBJ("collation","%Library.Username",.collval),! zw collval
1

Strangely, I had no issues with the %Library.Username type. I didn't explicitly specify the collation anywhere: neither in the data type class nor for the Namespace-wide.

Namespace '%SYS':

Class %Library.Username Extends %String
{

Parameter MAXLEN As INTEGER = 160;

}

Namespace 'USER':

Class dc.Username Extends %String
{

Parameter MAXLEN As INTEGER = 160;

}

Class dc.a Extends %Persistent
{

Index is1 On s1;

Index is2 On s2;

Index is3 On s3;

Property s1 As %String;

Property s2 As %Username;

Property s3 As dc.Username;

ClassMethod Test()
{
  d ..%KillExtent()
  
  f s="joefu","JoeFu" {
    s t=..%New()
    s t.s1=s
    s t.s2=s
    s t.s3=s
    d t.%Save()
  }

  zw ^dc.aD,^dc.aI
}

}

select FIELD_NAME,DATATYPE,COLLATION_FUNCTION,MAXLEN from %Library.SQLCatalog_SQLFields('dc.a')



FIELD_NAME
DATATYPE
COLLATION_FUNCTION
MAXLEN


ID
%Library.BigInt
(null)
(null)


s1
%Library.String
SQLUPPER
50


s2
%Library.Username
SQLUPPER
160


s3
dc.Username
SQLUPPER
160


x__classname
%Library.RawString
(null)
(null)


select INDEX_NAME,FIELDS from %Library.SQLCatalog_SQLIndices('dc.a')



INDEX_NAME
FIELDS


is1
$$SQLUPPER({dc.a.s1})


is2
$$SQLUPPER({dc.a.s2})


is3
$$SQLUPPER({dc.a.s3})


USER>d ##class(dc.a).Test()
^dc.aD=2
^dc.aD(1)=$lb("","joefu","joefu","joefu")
^dc.aD(2)=$lb("","JoeFu","JoeFu","JoeFu")
^dc.aI("is1"," JOEFU",1)=""
^dc.aI("is1"," JOEFU",2)=""
^dc.aI("is2"," JOEFU",1)=""
^dc.aI("is2"," JOEFU",2)=""
^dc.aI("is3"," JOEFU",1)=""
^dc.aI("is3"," JOEFU",2)=""

Specifying a Variable Number of Arguments

Take a look at Creating and Using Terminal Scripts

It seems to me that there is a typo in the TestStartBottomLeft method:

should be  Do $$$AssertEquals(##class(codeGolf.ClockwiseWord).Solution(.matrix, 3, 1), "781234569")

I'm not familiar with Ensemble, but it may be possible to replace the regular stream with the %Stream.GlobalCharacterSearchable class?

Please note the following warning:

Important:

There are known incompatibilities between InterSystems IRIS and Python 3.13, so you are advised to avoid Python 3.13 at this time. This issue will be addressed in an upcoming version of InterSystems IRIS.

That's right, the generated code lacks $GET or initial initialization of the variable.

Yes, these are fields that will either be inserted or updated.

PS:
In fact, the following query should work correctly:

INSERT OR UPDATE myTable SET name='Omer',  counter = NVL(counter,0) + 1 

But unfortunately, the SQL engine generates code where an undefined variable is accessed, so the <UNDEFINED> error occurs.
Try contacting WRC for a fix.