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(WIP) Allows the use of = instead of <- #2521

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(WIP) Allows the use of = instead of <- #2521

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eabdb9a
Allows the use of = instead of <-
J-Moravec Feb 21, 2024
445f40f
Fixed use_equal_assign name and position
J-Moravec Feb 22, 2024
a4fb906
Fix matched := when using 'allow_equal_assign'
J-Moravec Feb 23, 2024
1068861
Merge branch 'main' into equal_assignment_lintr
J-Moravec Oct 3, 2024
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14 changes: 11 additions & 3 deletions R/assignment_linter.R
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@
#' @param allow_right_assign Logical, default `FALSE`. If `TRUE`, `->` and `->>` are allowed.
#' @param allow_trailing Logical, default `TRUE`. If `FALSE` then assignments aren't allowed at end of lines.
#' @param allow_pipe_assign Logical, default `FALSE`. If `TRUE`, magrittr's `%<>%` assignment is allowed.
#' @param allow_equal_assign Logical, default `FALSE`.
#' If `TRUE`, `=` instead of `<-` is used for assignment.
#'
#' @examples
#' # will produce lints
Expand Down Expand Up @@ -73,7 +75,8 @@
assignment_linter <- function(allow_cascading_assign = TRUE,
allow_right_assign = FALSE,
allow_trailing = TRUE,
allow_pipe_assign = FALSE) {
allow_pipe_assign = FALSE,
allow_equal_assign = FALSE) {
trailing_assign_xpath <- paste(
collapse = " | ",
c(
Expand All @@ -88,7 +91,7 @@ assignment_linter <- function(allow_cascading_assign = TRUE,

xpath <- paste(collapse = " | ", c(
# always block = (NB: the parser differentiates EQ_ASSIGN, EQ_SUB, and EQ_FORMALS)
"//EQ_ASSIGN",
if (allow_equal_assign) "//LEFT_ASSIGN[text() = '<-']" else "//EQ_ASSIGN",
# -> and ->> are both 'RIGHT_ASSIGN'
if (!allow_right_assign) "//RIGHT_ASSIGN" else if (!allow_cascading_assign) "//RIGHT_ASSIGN[text() = '->>']",
# <-, :=, and <<- are all 'LEFT_ASSIGN'; check the text if blocking <<-.
Expand All @@ -108,7 +111,12 @@ assignment_linter <- function(allow_cascading_assign = TRUE,
}

operator <- xml_text(bad_expr)
lint_message_fmt <- rep("Use <-, not %s, for assignment.", length(operator))
lint_message_fmt <- rep(
paste0("Use ",
if (allow_equal_assign) "=" else "<-",
", not %s, for assignment."),
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length(operator)
)
lint_message_fmt[operator %in% c("<<-", "->>")] <-
"Replace %s by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior."
lint_message_fmt[operator == "%<>%"] <-
Expand Down
6 changes: 5 additions & 1 deletion man/assignment_linter.Rd
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11 changes: 11 additions & 0 deletions tests/testthat/test-assignment_linter.R
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Original file line number Diff line number Diff line change
Expand Up @@ -192,3 +192,14 @@ test_that("multiple lints throw correct messages", {
assignment_linter(allow_cascading_assign = FALSE)
)
})

test_that("= instead of <- can be used for assignment", {
linter <- assignment_linter(allow_equal_assign = TRUE)
lint_msg <- rex::rex("Use =, not <-, for assignment.")

expect_lint("blah = 1", NULL, linter)
expect_lint("blah <- 1", lint_msg, linter)

# data.table's left assign := needs to be silent
expect_lint("dt[, x := 42]", NULL, linter)
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Please add one more test for multiple lints. See L178-194 just above for an idea -- we're trying to insure that the new logic doesn't interact poorly with other options.

})
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