Feature Request: Typo Error Message

[jacobdornEcon]

Thank you for writing this package! I had a small quality-of-life suggestion.

Suppose one wanted to analyze the mpdta dataset:

data(mpdta)
did::att_gt(yname = "lemp", gname = "first.treat", idname = "countyreal", tname = "year",  data = mpdta)

However, suppose one (totally hypothetically) is silly and thinks it's a country-level dataset and runs:

data(mpdta)
did::att_gt(yname = "lemp", gname = "first.treat", idname = "countryreal", tname = "year",  data = mpdta)

The package gives an error:

Error in `[.data.frame`(data, , c(idname, tname, yname, gname, weightsname,  : 
  undefined columns selected

which is scary and not super helpful for debugging.

When you have a free moment, it might be nice to instead throw an error that includes setdiff(c(idname, tname, yname, gname, weightsname, ...), names(the_data_frame)) for easier typo-finding. Though it's certainly low priority!