duplicate warning in 1.9.7 - how to switch this off

[ghost]

I am using data.table 1.9.7.
when I run df[!duplicated(df), ]in a function I get this message:

Default value of duplicated.data.table method's 'by' argument will be changed to seq_along(x) (from key(x)) from the next release to be consistent with the default behaviour of base::unique.data.frame.

How do I switch this off? I have tried suppressMessages and checked that the verbose option in data.table is off. In the duplicated documentation I can't find what data.table wants me to do now.

[jangorecki]

Provide by=key(df) argument to duplicated call, you can also remove key from df - but because you do join here then adding on="oldkeycols" would be required. This messages is here to prevent from silently breaking the code on update to 1.9.8.

[arunsrinivasan]

Will improve message, and probably add a global option. Thanks.

[mattdowle]

As @arunsrinivasan suggested have now added a global option and moved the message to the startup banner. See commits to close #1284. Thanks for highlighting it @carbonmetrics.