Error occurs when adding fields with the same name

[carlineng]

Using the Baby Names example, first add gender, then add cohort.gender:

Composer crashes with the error Ambiguous output field name:

[christopherswenson]

Great catch — thanks for filing the issue. The language doesn't allow for multiple fields with the same "output" name in a query (gender and cohort.gender both have the same output name), and gives that error "Ambiguous output field name." if you try.

Probably the UI should force you to rename one of them if you try to do this.

[christopherswenson]

Independent of the fix, we should probably catch errors that result from bad generated queries and handle them more gracefully...

[whscullin]

Splitting unhandled exception out to #54

[tschomer]

perhaps we could rename things, so this works without the user having to figure things out.