nzchar() efficiently determines which of a vector of strings are empty
(i.e., are ""). It should in most cases be used instead of
constructions like string == "" or nchar(string) == 0.
Details
One crucial difference is in the default handling of NA_character_, i.e.,
missing strings. nzchar(NA_character_) is TRUE, while NA_character_ == ""
and nchar(NA_character_) == 0 are both NA. Therefore, for strict
compatibility, use nzchar(x, keepNA = TRUE). If the input is known to be
complete (no missing entries), this argument can be dropped for conciseness.
See also
linters for a complete list of linters available in lintr.
Examples
# will produce lints
lint(
text = "x[x == '']",
linters = nzchar_linter()
)
#> ::warning file=<text>,line=1,col=3::file=<text>,line=1,col=3,[nzchar_linter] Use !nzchar(x) instead of x == "". Note that unlike nzchar(), EQ coerces to character, so you'll have to use as.character() if x is a factor. Whenever missing data is possible, please take care to use nzchar(., keepNA = TRUE); nzchar(NA) is TRUE by default.
lint(
text = "x[nchar(x) > 0]",
linters = nzchar_linter()
)
#> ::warning file=<text>,line=1,col=3::file=<text>,line=1,col=3,[nzchar_linter] Use nzchar(x) instead of nchar(x) > 0. Whenever missing data is possible, please take care to use nzchar(., keepNA = TRUE); nzchar(NA) is TRUE by default.
# okay
lint(
text = "x[!nzchar(x, keepNA = TRUE)]",
linters = nzchar_linter()
)
lint(
text = "x[nzchar(x, keepNA = TRUE)]",
linters = nzchar_linter()
)