Hey @lloydtabb I'd like to work on this issue

I did some initial investigation:

1. the core issue seems to be that for the order_by field to be processed correctly by a call to getField it must be in the resultStruct. field list. That's why uncommenting aggregate will make the query succeed, as airport_count is in the field list for the resultStruct by the time it is asked for by the order by code.

2. A good place to make the fix seems to be in

   malloy/packages/malloy/src/model/malloy_query.ts

   Line 1930 in 8394aed

   expandFields(resultStruct: FieldInstanceResult) {

   
   namely, change the loop on 1932, to also process the order by field for a segment.

3. Unfortunately, orderBy is not of type QueryField which is the required type for a call to addField

   malloy/packages/malloy/src/model/malloy_query.ts

   Line 1015 in 8394aed

   addField(as: string, field: QueryField, usage: FieldUsage) {

So the proposed solution is to turn QuerySegment#orderBy into a QueryField type so it can be used as an argument to addField

Does that approach sound sensible? Are there pitfalls you can think of?