Test suite warnings from missing compute function

[dylan-stark]

Warnings are issued from ggproto_formals(calculate) call in test-function-args.r when using R 3.4.1.

In each case, calculate is NULL and so the string name of the function is passed to .Internal(formals(fun)). It looks like the warning for this case (and a TODO comment to stop on this condition in the future) was added in R 3.4.0.

From what I can see, compute was changed to compute_panel in a previous commit. And I verified that making the same update in the test fixes the issue -- I'm happy to put together a PR with that patch if that's sufficient.

To reproduce, go to the package root and use the following with R >= 3.4.0 to see the warnings:

devtools::test(pkg = "/home/rstudio/ggplot2", filter = "function-args")
#> Loading ggplot2
#> Loading required package: testthat
#> Testing ggplot2
#> function-args: ............................................W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.W.
#> 
#> Warnings ------------------------------------------------------------------
#> 1. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 2. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 3. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 4. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 5. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 6. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 7. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 8. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 9. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 10. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 11. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 12. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 13. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 14. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 15. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 16. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 17. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 18. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 19. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 20. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 21. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 22. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 23. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 24. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 25. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 26. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> 27. stat_xxx and StatXxx$draw arg defaults match (@test-function-args.r#59) - argument is not a function
#> 
#> DONE ======================================================================

[karawoo]

Yeah I've been getting these warnings (and studiously putting off dealing with them for the time being 😜) as well. Your fix seems right to me. It looks like there are also some comments in the stat tests that were directly copied from the geom section above and should be updated. A PR would be welcome!