`columnnames` sometimes returns property names

[ParadaCarleton]

using CSV
data = CSV.load("filepath.csv")
Tables.columnnames(data)
# returns (:filename, :delim, :keywords)--property names--instead of column names

[bkamins]

Indeed type returned by CSV.load seems to need to override the default return-value (or define getproperty differently)

[ParadaCarleton]

Yep. Besides that, is the default (automatically return properties) a good default, or should it error for types that don't have a defined method?

[quinnj]

The default has always been to return propertynames.

[juliohm]

The linked issue #338 is a good resource. The Tables.columnnames trait is only safe in the result of Tables.columns. The table itself doesn't store the names of columns. After playing with this design decision for a while, I think it makes sense. Specially because it is hard to introduce fallbacks in Tables.jl with a "catch-all" types dispatch (there is no parent type).