Ignore srcrefs by default in expect_identical()

[lionel-]

cc @kalibera @hadley

And forward ... to identical() for more control.

[jimhester]

R 3.4.0 and up has a default of identical(ignore.srcref = TRUE). Prior to that there is no option. It seems unwise for testthat to mess with the objects source references in expect_identical() so I don't think there is much else to do other than pass ... to identical().

[lionel-]

Compatibility aside I think it'd be preferable to ignore the srcrefs attributes by default since their presence depends on things like the editor. I wouldn't call it unwise. Tomas plans to enable srcrefs by default and that might cause check failures:

I found that rlang fails its own tests when packages have source references (now can be enabled with R_KEEP_PKG_SOURCE=yes and re-installing packages/rebuilding R, but I would like to make this a default, if the space and performance overhead is small enough)

I see very few use cases for testing presence and equality of srcrefs attributes.

[jimhester]

They are ignored by default in 3.4 and up, so if they are turned on in the future they will already be ignored.

[lionel-]

Ah that makes sense.