[R-pkg-devel] What counts as an API change?

[David Hugh-Jones]

Hi all,

Philosophical question. My package follows semantic versioning (
https://semver.org). Incompatible API changes should trigger a major
version upgrade. OK, but what counts as an incompatible change to an R API?
Suppose my current function signature is

foo <- function (a, b, c, d)

and the new one is

foo <- function (a, b, c, d, e)

is that compatible? What if I add an argument, but not at the end:

foo <- function (a, b, c, e, d)

That would be incompatible if people have been calling the arguments by
order rather than by name. But sometimes that is unlikely: I doubt if many
people write

lm(y ~ x, mydata, z==3, f, na.omit, "qr", FALSE, FALSE, TRUE, TRUE, FALSE)

Should I be strict or relaxed about this?

Cheers,
David

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