[ci] [R-package] Add class_equals linter (#5307)

.ci/lint_r_code.R

@@ -33,6 +33,7 @@ LINTERS_TO_USE <- list(
     , "any_is_na_linter"     = lintr::any_is_na_linter()
     , "assignment"           = lintr::assignment_linter()
     , "braces"               = lintr::brace_linter()
+    , "class_equals_linter"  = lintr::class_equals_linter()
     , "commas"               = lintr::commas_linter()
     , "equals_na"            = lintr::equals_na_linter()
     , "function_left"        = lintr::function_left_parentheses_linter()

R-package/R/utils.R

 lgb.is.Booster <- function(x) {
-  return(all(c("R6", "lgb.Booster") %in% class(x)))
+  return(all(c("R6", "lgb.Booster") %in% class(x)))  # nolint: class_equals_linter
 }
 
 lgb.is.Dataset <- function(x) {
-  return(all(c("R6", "lgb.Dataset") %in% class(x)))
+  return(all(c("R6", "lgb.Dataset") %in% class(x)))  # nolint: class_equals_linter
 }
 
 lgb.is.Predictor <- function(x) {
-  return(all(c("R6", "lgb.Predictor") %in% class(x)))
+  return(all(c("R6", "lgb.Predictor") %in% class(x)))  # nolint: class_equals_linter
 }
 
 lgb.is.null.handle <- function(x) {