[R] replace uses of T and F with TRUE and FALSE (#5778)

* [R-package] replace uses of T and F with TRUE and FALSE

* enable linting

* Remove skip

Co-authored-by: Philip Hyunsu Cho <chohyu01@cs.washington.edu>

R-package/tests/testthat/test_helpers.R

@@ -12,7 +12,7 @@ flag_32bit = .Machine$sizeof.pointer != 8
 
 set.seed(1982)
 data(Arthritis)
-df <- data.table(Arthritis, keep.rownames = F)
+df <- data.table(Arthritis, keep.rownames = FALSE)
 df[,AgeDiscret := as.factor(round(Age / 10,0))]
 df[,AgeCat := as.factor(ifelse(Age > 30, "Old", "Young"))]
 df[,ID := NULL]
@@ -47,7 +47,7 @@ test_that("xgb.dump works", {
   if (!flag_32bit)
     expect_length(xgb.dump(bst.Tree), 200)
   dump_file = file.path(tempdir(), 'xgb.model.dump')
-  expect_true(xgb.dump(bst.Tree, dump_file, with_stats = T))
+  expect_true(xgb.dump(bst.Tree, dump_file, with_stats = TRUE))
   expect_true(file.exists(dump_file))
   expect_gt(file.size(dump_file), 8000)
 
@@ -160,7 +160,7 @@ test_that("SHAPs sum to predictions, with or without DART", {
           objective = "reg:squarederror",
           eval_metric = "rmse"),
         if (booster == "dart")
-          list(rate_drop = .01, one_drop = T)),
+          list(rate_drop = .01, one_drop = TRUE)),
       data = d,
       label = y,
       nrounds = nrounds)
@@ -168,8 +168,8 @@ test_that("SHAPs sum to predictions, with or without DART", {
     pr <- function(...)
       predict(fit, newdata = d, ...)
     pred <- pr()
-    shap <- pr(predcontrib = T)
-    shapi <- pr(predinteraction = T)
+    shap <- pr(predcontrib = TRUE)
+    shapi <- pr(predinteraction = TRUE)
     tol = 1e-5
 
     expect_equal(rowSums(shap), pred, tol = tol)

R-package/tests/testthat/test_interactions.R

@@ -107,7 +107,7 @@ test_that("SHAP contribution values are not NAN", {
 
   shaps <- as.data.frame(predict(fit,
     newdata = as.matrix(subset(d, fold == 1)[, ivs]),
-    predcontrib = T))
+    predcontrib = TRUE))
   result <- cbind(shaps, sum = rowSums(shaps), pred = predict(fit,
       newdata = as.matrix(subset(d, fold == 1)[, ivs])))
 

R-package/tests/testthat/test_lint.R

@@ -1,8 +1,6 @@
 context("Code is of high quality and lint free")
 test_that("Code Lint", {
   skip_on_cran()
-  skip_on_travis()
-  skip_if_not_installed("lintr")
   my_linters <- list(
     absolute_paths_linter=lintr::absolute_paths_linter,
     assignment_linter=lintr::assignment_linter,
@@ -21,7 +19,8 @@ test_that("Code Lint", {
     spaces_inside_linter=lintr::spaces_inside_linter,
     spaces_left_parentheses_linter=lintr::spaces_left_parentheses_linter,
     trailing_blank_lines_linter=lintr::trailing_blank_lines_linter,
-    trailing_whitespace_linter=lintr::trailing_whitespace_linter
+    trailing_whitespace_linter=lintr::trailing_whitespace_linter,
+    true_false=lintr::T_and_F_symbol_linter
   )
-  # lintr::expect_lint_free(linters=my_linters) # uncomment this if you want to check code quality
+  lintr::expect_lint_free(linters=my_linters) # uncomment this if you want to check code quality
 })