Usage of & in conditional statements is error-prone and inefficient.
condition in if (condition) expr must always be length-1, in which
case && is to be preferred. Ditto for | vs. ||.
vector_logic_linter()best_practices, default, efficiency
This linter covers inputs to if() and while() conditions and to
testthat::expect_true() and testthat::expect_false().
Note that because & and | are generics, it is possible that
&& / || are not perfect substitutes because & is doing
method dispatch in an incompatible way.
Moreover, be wary of code that may have side effects, most commonly
assignments. Consider if ((a <- foo(x)) | (b <- bar(y))) { ... }
vs. if ((a <- foo(x)) || (b <- bar(y))) { ... }. Because || exits
early, if a is TRUE, the second condition will never be evaluated
and b will not be assigned. Such usage is not allowed by the Tidyverse
style guide, and the code can easily be refactored by pulling the
assignment outside the condition, so using || is still preferable.
linters for a complete list of linters available in lintr.
https://style.tidyverse.org/syntax.html#if-statements