evaluate operator: wildcard `*` in output schema drops source columns

[OwenBinchy]

Hi,
I'm building an offline KQL validator using Kusto.Language and hit an issue with evaluate output schemas that use *.

The issue: * in the output schema should preserve source columns (per the docs), but the parser drops them.

Reproduction

var db = new DatabaseSymbol("testdb",
  new TableSymbol("T", "(Id: string, Data: dynamic)"));
var cluster = new ClusterSymbol("test", db);
var globals = GlobalState.Default.AddOrReplaceCluster(cluster).WithCluster(cluster).WithDatabase(db);

var code = KustoCode.ParseAndAnalyze(
  "T | evaluate bag_unpack(Data) : (*, x: long, y: long)", globals);

var result = code.ResultType as TableSymbol;
// Actual:   [x, y]          — Id is missing
// Expected: [Id, x, y]      — Id preserved by *

Runtime comparison

datatable(Id:string, Data:dynamic) ["a", dynamic({"x": 1, "y": 2})]
| evaluate bag_unpack(Data) : (*, x: long, y: long)
| getschema

Runtime returns Id:string, x:long, y:long — all 3 columns present.

Without the schema hint, bag_unpack correctly returns [Id] [open]. But adding : (*, x, y) loses Id.

Root cause

VisitEvaluateOperator calls
CreateColumnsFromRowSchema on node.Schema.Schema.Columns, but never checks node.Schema.Schema.AsteriskToken — which the
grammar already parses and stores. Looks like the asterisk handling was missed when EvaluateRowSchema was introduced in
2f35577f.

Proposed fix

Insert before the existing CreateColumnsFromRowSchema call in VisitEvaluateOperator:

if (node.Schema.Schema.AsteriskToken != null && node.Schema.Schema.AsteriskToken.Width > 0)
{
  var pluginResult = GetResultTypeOrError(node.FunctionCall) as TableSymbol;
  if (pluginResult != null)
  {
      var explicitNames = new HashSet<string>();
      for (int i = 0; i < node.Schema.Schema.Columns.Count; i++)
          explicitNames.Add(node.Schema.Schema.Columns[i].Element.Name.SimpleName);

      foreach (var col in pluginResult.Columns)
      {
          if (!explicitNames.Contains(col.Name))
              columns.Add(col);
      }
  }
}
CreateColumnsFromRowSchema(node.Schema.Schema.Columns, columns);

Tested locally with 24 tests (bag_unpack, pivot, chained plugins, column conflicts, non-evaluate regressions).

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Note: investigation and fix development were done with AI assistance (GitHub Copilot).