implicit_assignment

Added in 0.0.17

What it does

Checks for implicit assignment in function calls and other situations.

Why is this bad?

Assigning inside function calls or other situations such as in if() makes the code difficult to read, and should be avoided.

Configuration options

The operation of the implicit_assignment rule can be customised in the configuration file.

Use skipped-functions to fully replace the default list of functions that are allowed to contain implicit assignment. Use extend-skipped-functions to add to the default list. Specifying both is an error.

Function names in skipped-functions or extend-skipped-functions also match namespaced calls, e.g. skipped-functions = ["list2"] will ignore list2() and rlang::list2().

Default values

skipped-functions = [
    "alist",
    "expect_error",         # from {testthat}
    "expect_warning",       # from {testthat}
    "expect_message",       # from {testthat}
    "expect_silent",        # from {testthat}
    "expect_defunct",       # from {lifecycle}
    "expect_deprecated",    # from {lifecycle}
    "expect_snapshot",      # from {testthat}
    "expect_no_condition",  # from {testthat}
    "expect_no_warning",    # from {testthat}
    "expect_no_error",      # from {testthat}
    "expect_no_message",    # from {testthat}
    "quote",
    "suppressMessages",
    "suppressWarnings",
    "try"
]

TOML settings

[lint]
...

[lint.implicit_assignment]
# Ignore implicit assignment in `list()` only.
skipped-functions = ["list"]

Example

mean(x <- c(1, 2, 3))
x

if (any(y <- x > 0)) {
  print(y)
}

Use instead:

x <- c(1, 2, 3)
mean(x)
x

larger <- x > 0
if (any(larger)) {
  print(larger)
}

References

See:

https://style.tidyverse.org/syntax.html#assignment