Don't lint T and F if followed by [ (r-lib#2947)

* Don't lint T and F if followed by `[`.

* Address review comments.

* subsume into same expr[] as $ and @

---------

Co-authored-by: Michael Chirico <[email protected]>

Author: 2 people

NEWS.md

@@ -74,6 +74,7 @@ files in Windows (#2882, @Bisaloo).
 * `assignment_linter()` with `operator = "="` does a better job of skipping implicit assignments, which are intended to be governed by `implicit_assignment_linter()` (#2765, @MichaelChirico).
 * `expect_true_false_linter()` is pipe-aware, so that `42 |> expect_identical(x, ignore_attr = TRUE)` no longer lints (#1520, @MichaelChirico).
 * `T_and_F_symbol_linter()` ignores `T` and `F` used as symbols in formulas (`y ~ T + F`), which can represent variables in data not controlled by the author (#2637, @MichaelChirico).
+* `T_and_F_symbol_linter()` ignores `T` and `F` if followed by `[` or `[[` (#2944, @mcol).
 * `implicit_assignment_linter()` with `allow_scoped=TRUE` doesn't lint for `if (a <- 1) print(a)` (#2913, @MichaelChirico).
 
 ### Lint accuracy fixes: removing false negatives

R/T_and_F_symbol_linter.R

@@ -34,7 +34,7 @@
 T_and_F_symbol_linter <- function() { # nolint: object_name.
   symbol_xpath <- "//SYMBOL[
     (text() = 'T' or text() = 'F')
-    and not(parent::expr[OP-DOLLAR or OP-AT])
+    and not(parent::expr[OP-DOLLAR or OP-AT or following-sibling::OP-LEFT-BRACKET or following-sibling::LBB])
     and (
       not(ancestor::expr[OP-TILDE])
       or parent::expr/preceding-sibling::*[not(self::COMMENT)][1][self::EQ_SUB]

tests/testthat/test-T_and_F_symbol_linter.R

@@ -7,6 +7,8 @@ test_that("T_and_F_symbol_linter skips allowed usages", {
   expect_no_lint("y ~ T + F", linter)
   expect_no_lint("y ~ x + I(T^2)", linter)
   expect_no_lint("y ~ foo(T, F)", linter)
+  expect_no_lint("T[1]", linter)
+  expect_no_lint("T[[1]]", linter)
 })
 
 test_that("T_and_F_symbol_linter blocks disallowed usages", {
@@ -32,6 +34,8 @@ test_that("T_and_F_symbol_linter blocks disallowed usages", {
   expect_lint("DF$bool <- T", msg_true, linter)
   expect_lint("S4@bool <- T", msg_true, linter)
   expect_lint("sum(x, na.rm = T)", msg_true, linter)
+  expect_lint("x[T]", msg_true, linter)
+  expect_lint("x[, cols, drop = T]", msg_true, linter)
   expect_lint("y ~ foo(x, arg = T)", msg_true, linter)
   expect_lint(
     trim_some("