Discrepancy between grid summary and group summary formatting

I cannot get this to work the way I want after much trial and error. I want the grid summary and the group summary to be handled the exact same way.

I am happy with the way the grid summary is formatted. It is showing blank. But, it seems like the group summary is controlled by formatCellValue. I tried using formatGroupSummary like you see in the code below. But, it isn't having any effect. So, how can I have a summary function on the Unit Price column in this example that returns a blank instead of an NA for the group summary? Am I doing something wrong in the way I'm trying to use formatGroupSummary? To me, it seems like the group summary is tied to formatCellValue whereas the grid summary is not.

I hope you understand I have simplified my example from our production application to provide you a simple test case. We want to define a summary function for every column. But, we want the summary function to show a blank value even if formatCellValue shows an NA for the individual cells. And, we want it to work consistently between the group summaries and the grid summaries.

isc.ListGrid.create({
    ID: "companyList",
    width:600, height:520,
    alternateRecordStyles:true,
    autoFetchData:true,
    dataSource:orderItemLocalDS,
    showAllRecords:true,
    groupByField:"category", groupStartOpen:"all",
    canEdit:true, editEvent:"click",
    
    showGridSummary:true,
    showGroupSummary:true,
    fields:[
        {name:"orderID", includeInRecordSummary:false, summaryFunction:"count"},
        {name:"itemDescription"},
        {name:"category", showGridSummary:true, 
            getGridSummary:function (records, summaryField) {
                var seenCategories = {};
                for (var i = 0; i < records.length; i++) {
                    seenCategories[records[i].category] = true;
                }
                var totalCategories = isc.getKeys(seenCategories).length;
                return totalCategories + " Categories";
                
            }
        },
        {name:"shipDate", showGroupSummary:true, showGridSummary:false, summaryFunction:"max"},
        
        {name:"quantity", showGroupSummary:false, showGridSummary:false},
        {name:"unitPrice", showGroupSummary:true, showGridSummary:true,
         formatCellValue:function (value) {
             if (isc.isA.Number(value)) {
                return value.toCurrencyString("$");
             }
             return "NA";
         },
         formatGroupSummary:function (value) {
             if (isc.isA.Number(value)) {
                return value.toCurrencyString("$");
             }
             return null;
         },
        summaryFunction:"return null"
        },
        {name:"Total", type:"summary", recordSummaryFunction:"multiplier",
         summaryFunction:"sum",
         showGridSummary:true, showGroupSummary:true,
         align:"right",
         formatCellValue:function (value) {
             if (isc.isA.Number(value)) {
                return value.toCurrencyString("$");
             }
             return value;
         }
        }
    ]
})

[Isomorphic]

We see the discrepancy. The issue is basically that when a group-summary row has a calculated value of 'null', it applies the invalidSummaryValue to the cell, but then runs the standard 'formatCellValue()' method on top of that, whereas when a grid summary has a calculated value of null it does not run through formatCellValue(). Clearly the behavior should be the same in both cases. We're looking at how best to resolve this in the code.

However for now the easiest way to get things running will be to modify your formatter to handle being passed a group, or grid summary row:

        {name:"unitPrice", showGroupSummary:true, showGridSummary:true,
         formatCellValue:function (value, record, rowNum, colNum, grid) {
             if (isc.isA.Number(value)) {
                return value.toCurrencyString("$");
             }
             if (record.isGroupSummary || record.isGridSummary) return " ";
             return "NA";
         },
        summaryFunction:"return null"
        },

Thank you. That tweak will work for now.

[Isomorphic]

A quick update to let you know that we've resolved these discrepancies in the 8.3d branch.
However the change we made to get this working, while not drastic, is moderately involved and given that the solution suggested here should work for you we don't plan to immediately port across to 8.2p.

If this is going to prove unacceptable (for example you find you can't get the behavior you need out of 8.2 after all), let us know and we'll update 8.2

Thanks for the update. I believe the workaround is sufficient for me so no need to port to 8.2.