[R-package] Add explicit return statement to R functions. (#3703)

* add explicit return statement to functions in callback.R

* add explicit return statement to functions in lgb.Booster.R

* add explicit return statement to functions in lgb.Dataset.R

* add explicit return statement to functions in lgb.Predictor.R

* add explicit return statement to functions in lgb.cv.R

* add explicit return statement to functions in lgb.interprete.R

* add explicit return statement to functions in lgb.plot.importance.R

* add explicit return statement to functions in saveRDS.lgb.Booster.R

* add explicit return statement to functions in utils.R

* add explicit return statement to functions in lgb.plot.interpretation.R

* add explicit return statement to functions in build_r.R

* fix typo

* return(self) -> return(invisible(self))

* fix some inconsistent indention

* fix test failure

* add another return() statement

* fix linting errors

R-package/R/aliases.R

@@ -7,7 +7,8 @@
 # [return] A named list, where each key is a parameter relevant to lgb.DataSet and each value is a character
 #          vector of corresponding aliases.
 .DATASET_PARAMETERS <- function() {
-    return(list(
+    return(
+        list(
             "bin_construct_sample_cnt" = c(
                 "bin_construct_sample_cnt"
                 , "subsample_for_bin"
@@ -74,7 +75,8 @@
                 , "weight"
             )
             , "zero_as_missing" = "zero_as_missing"
-    ))
+        )
+    )
 }
 
 # [description] List of respected parameter aliases. Wrapped in a function to take advantage of
@@ -115,10 +117,12 @@
 # [returns]
 #     A character vector
 .NO_METRIC_STRINGS <- function() {
-    return(c(
+    return(
+        c(
             "na"
             , "None"
             , "null"
             , "custom"
-    ))
+        )
+    )
 }

R-package/R/callback.R

@@ -74,6 +74,8 @@ cb.reset.parameters <- function(new_params) {
 
     }
 
+    return(invisible(NULL))
+
   }
 
   callback <- function(env) {
@@ -95,15 +97,17 @@ cb.reset.parameters <- function(new_params) {
     })
 
     if (!is.null(env$model)) {
-      env$model$reset_parameter(params = pars)
+      return(env$model$reset_parameter(params = pars))
     }
 
+    return(invisible(NULL))
+
   }
 
   attr(callback, "call") <- match.call()
   attr(callback, "is_pre_iteration") <- TRUE
   attr(callback, "name") <- "cb.reset.parameters"
-  callback
+  return(callback)
 }
 
 # Format the evaluation metric string
@@ -116,9 +120,9 @@ format.eval.string <- function(eval_res, eval_err = NULL) {
 
   # Check for empty evaluation error
   if (!is.null(eval_err)) {
-    sprintf("%s\'s %s:%g+%g", eval_res$data_name, eval_res$name, eval_res$value, eval_err)
+    return(sprintf("%s\'s %s:%g+%g", eval_res$data_name, eval_res$name, eval_res$value, eval_err))
   } else {
-    sprintf("%s\'s %s:%g", eval_res$data_name, eval_res$name, eval_res$value)
+    return(sprintf("%s\'s %s:%g", eval_res$data_name, eval_res$name, eval_res$value))
   }
 
 }
@@ -150,7 +154,7 @@ merge.eval.string <- function(env) {
 
   }
 
-  paste0(msg, collapse = "  ")
+  return(paste0(msg, collapse = "  "))
 
 }
 
@@ -180,13 +184,15 @@ cb.print.evaluation <- function(period = 1L) {
 
     }
 
+    return(invisible(NULL))
+
   }
 
   # Store attributes
   attr(callback, "call") <- match.call()
   attr(callback, "name") <- "cb.print.evaluation"
 
-  callback
+  return(callback)
 
 }
 
@@ -253,13 +259,15 @@ cb.record.evaluation <- function() {
 
     }
 
+    return(invisible(NULL))
+
   }
 
   # Store attributes
   attr(callback, "call") <- match.call()
   attr(callback, "name") <- "cb.record.evaluation"
 
-  callback
+  return(callback)
 
 }
 
@@ -311,6 +319,8 @@ cb.early.stop <- function(stopping_rounds, first_metric_only = FALSE, verbose =
 
     }
 
+    return(invisible(NULL))
+
   }
 
   # Create callback
@@ -392,18 +402,21 @@ cb.early.stop <- function(stopping_rounds, first_metric_only = FALSE, verbose =
         env$met_early_stop <- TRUE
       }
     }
+
+    return(invisible(NULL))
+
   }
 
   attr(callback, "call") <- match.call()
   attr(callback, "name") <- "cb.early.stop"
 
-  callback
+  return(callback)
 
 }
 
 # Extract callback names from the list of callbacks
 callback.names <- function(cb_list) {
-  unlist(lapply(cb_list, attr, "name"))
+  return(unlist(lapply(cb_list, attr, "name")))
 }
 
 add.cb <- function(cb_list, cb) {
@@ -426,13 +439,14 @@ add.cb <- function(cb_list, cb) {
   }
 
   # Return element
-  cb_list
+  return(cb_list)
 
 }
 
 categorize.callbacks <- function(cb_list) {
 
   # Check for pre-iteration or post-iteration
+  return(
     list(
       pre_iter = Filter(function(x) {
         pre <- attr(x, "is_pre_iteration")
@@ -443,5 +457,6 @@ categorize.callbacks <- function(cb_list) {
         is.null(pre) || !pre
       }, cb_list)
     )
+  )
 
 }

R-package/R/lgb.Booster.R

@@ -21,6 +21,8 @@ Booster <- R6::R6Class(
 
       }
 
+      return(invisible(NULL))
+
     },
 
     # Initialize will create a starter booster
@@ -137,6 +139,8 @@ Booster <- R6::R6Class(
 
       self$params <- params
 
+      return(invisible(NULL))
+
     },
 
     # Set training data name
@@ -320,11 +324,13 @@ Booster <- R6::R6Class(
     current_iter = function() {
 
       cur_iter <- 0L
+      return(
         lgb.call(
           fun_name = "LGBM_BoosterGetCurrentIteration_R"
           , ret = cur_iter
           , private$handle
         )
+      )
 
     },
 
@@ -332,11 +338,13 @@ Booster <- R6::R6Class(
     upper_bound = function() {
 
       upper_bound <- 0.0
+      return(
         lgb.call(
           fun_name = "LGBM_BoosterGetUpperBoundValue_R"
           , ret = upper_bound
           , private$handle
         )
+      )
 
     },
 
@@ -344,11 +352,13 @@ Booster <- R6::R6Class(
     lower_bound = function() {
 
       lower_bound <- 0.0
+      return(
         lgb.call(
           fun_name = "LGBM_BoosterGetLowerBoundValue_R"
           , ret = lower_bound
           , private$handle
         )
+      )
 
     },
 
@@ -397,17 +407,19 @@ Booster <- R6::R6Class(
       }
 
       # Evaluate data
+      return(
         private$inner_eval(
           data_name = name
           , data_idx = data_idx
           , feval = feval
         )
+      )
 
     },
 
     # Evaluation training data
     eval_train = function(feval = NULL) {
-      private$inner_eval(private$name_train_set, 1L, feval)
+      return(private$inner_eval(private$name_train_set, 1L, feval))
     },
 
     # Evaluation validation data
@@ -463,12 +475,14 @@ Booster <- R6::R6Class(
       }
 
       # Return model string
-      return(lgb.call.return.str(
+      return(
+        lgb.call.return.str(
           fun_name = "LGBM_BoosterSaveModelToString_R"
           , private$handle
           , as.integer(num_iteration)
           , as.integer(feature_importance_type)
-      ))
+        )
+      )
 
     },
 
@@ -480,12 +494,14 @@ Booster <- R6::R6Class(
         num_iteration <- self$best_iter
       }
 
+      return(
         lgb.call.return.str(
           fun_name = "LGBM_BoosterDumpModel_R"
           , private$handle
           , as.integer(num_iteration)
           , as.integer(feature_importance_type)
         )
+      )
 
     },
 
@@ -510,6 +526,7 @@ Booster <- R6::R6Class(
 
       # Predict on new data
       predictor <- Predictor$new(private$handle, ...)
+      return(
         predictor$predict(
           data = data
           , start_iteration = start_iteration
@@ -520,12 +537,13 @@ Booster <- R6::R6Class(
           , header = header
           , reshape = reshape
         )
+      )
 
     },
 
     # Transform into predictor
     to_predictor = function() {
-      Predictor$new(private$handle)
+      return(Predictor$new(private$handle))
     },
 
     # Used for save
@@ -537,6 +555,8 @@ Booster <- R6::R6Class(
       # Overwrite model in object
       self$raw <- self$save_model_to_string(NULL)
 
+      return(invisible(NULL))
+
     }
 
   ),
@@ -780,6 +800,7 @@ predict.lgb.Booster <- function(object,
   }
 
   # Return booster predictions
+  return(
     object$predict(
       data = data
       , start_iteration = start_iteration
@@ -791,6 +812,7 @@ predict.lgb.Booster <- function(object,
       , reshape = reshape
       , ...
     )
+  )
 }
 
 #' @name lgb.load
@@ -896,10 +918,12 @@ lgb.save <- function(booster, filename, num_iteration = NULL) {
   }
 
   # Store booster
+  return(
     invisible(booster$save_model(
       filename = filename
       , num_iteration = num_iteration
     ))
+  )
 
 }
 
@@ -941,7 +965,7 @@ lgb.dump <- function(booster, num_iteration = NULL) {
   }
 
   # Return booster at requested iteration
-  booster$dump_model(num_iteration =  num_iteration)
+  return(booster$dump_model(num_iteration =  num_iteration))
 
 }
 
@@ -1045,5 +1069,5 @@ lgb.get.eval.result <- function(booster, data_name, eval_name, iters = NULL, is_
   iters <- iters - delta
 
   # Return requested result
-  as.numeric(result[iters])
+  return(as.numeric(result[iters]))
 }

R-package/R/lgb.Dataset.R

@@ -18,6 +18,8 @@ Dataset <- R6::R6Class(
 
       }
 
+      return(invisible(NULL))
+
     },
 
     # Initialize will create a starter dataset
@@ -85,6 +87,8 @@ Dataset <- R6::R6Class(
       private$info <- info
       private$version <- 0L
 
+      return(invisible(NULL))
+
     },
 
     create_valid = function(data,
@@ -325,6 +329,7 @@ Dataset <- R6::R6Class(
         num_col <- 0L
 
         # Get numeric data and numeric features
+        return(
           c(
             lgb.call(
               fun_name = "LGBM_DatasetGetNumData_R"
@@ -337,12 +342,13 @@ Dataset <- R6::R6Class(
               , private$handle
             )
           )
+        )
 
       } else if (is.matrix(private$raw_data) || methods::is(private$raw_data, "dgCMatrix")) {
 
         # Check if dgCMatrix (sparse matrix column compressed)
         # NOTE: requires Matrix package
-        dim(private$raw_data)
+        return(dim(private$raw_data))
 
       } else {
 
@@ -368,12 +374,12 @@ Dataset <- R6::R6Class(
             , private$handle
         )
         private$colnames <- as.character(base::strsplit(cnames, "\t")[[1L]])
-        private$colnames
+        return(private$colnames)
 
       } else if (is.matrix(private$raw_data) || methods::is(private$raw_data, "dgCMatrix")) {
 
         # Check if dgCMatrix (sparse matrix column compressed)
-        colnames(private$raw_data)
+        return(colnames(private$raw_data))
 
       } else {
 
@@ -470,7 +476,7 @@ Dataset <- R6::R6Class(
         }
       }
 
-      private$info[[name]]
+      return(private$info[[name]])
 
     },
 
@@ -522,6 +528,7 @@ Dataset <- R6::R6Class(
     slice = function(idxset, ...) {
 
       # Perform slicing
+      return(
         Dataset$new(
           data = NULL
           , params = private$params
@@ -534,6 +541,7 @@ Dataset <- R6::R6Class(
           , info = NULL
           , ...
         )
+      )
 
     },
 
@@ -679,7 +687,7 @@ Dataset <- R6::R6Class(
       if (lgb.is.null.handle(x = private$handle)) {
         self$construct()
       }
-      private$handle
+      return(private$handle)
 
     },
 
@@ -753,6 +761,7 @@ lgb.Dataset <- function(data,
                         ...) {
 
   # Create new dataset
+  return(
     invisible(Dataset$new(
       data = data
       , params = params
@@ -765,6 +774,7 @@ lgb.Dataset <- function(data,
       , info = info
       , ...
     ))
+  )
 
 }
 
@@ -796,7 +806,7 @@ lgb.Dataset.create.valid <- function(dataset, data, info = list(), ...) {
   }
 
   # Create validation dataset
-  invisible(dataset$create_valid(data = data, info = info, ...))
+  return(invisible(dataset$create_valid(data = data, info = info, ...)))
 
 }
 
@@ -822,7 +832,7 @@ lgb.Dataset.construct <- function(dataset) {
   }
 
   # Construct the dataset
-  invisible(dataset$construct())
+  return(invisible(dataset$construct()))
 
 }
 
@@ -856,7 +866,7 @@ dim.lgb.Dataset <- function(x, ...) {
     stop("dim.lgb.Dataset: input data should be an lgb.Dataset object")
   }
 
-  x$dim()
+  return(x$dim())
 
 }
 
@@ -893,7 +903,7 @@ dimnames.lgb.Dataset <- function(x) {
   }
 
   # Return dimension names
-  list(NULL, x$get_colnames())
+  return(list(NULL, x$get_colnames()))
 
 }
 
@@ -932,7 +942,7 @@ dimnames.lgb.Dataset <- function(x) {
 
   # Set column names properly, and return
   x$set_colnames(colnames = value[[2L]])
-  x
+  return(x)
 
 }
 
@@ -970,7 +980,7 @@ slice.lgb.Dataset <- function(dataset, idxset, ...) {
   }
 
   # Return sliced set
-  invisible(dataset$slice(idxset = idxset, ...))
+  return(invisible(dataset$slice(idxset = idxset, ...)))
 
 }
 
@@ -1020,7 +1030,7 @@ getinfo.lgb.Dataset <- function(dataset, name, ...) {
     stop("getinfo.lgb.Dataset: input dataset should be an lgb.Dataset object")
   }
 
-  dataset$getinfo(name = name)
+  return(dataset$getinfo(name = name))
 
 }
 
@@ -1074,7 +1084,7 @@ setinfo.lgb.Dataset <- function(dataset, name, info, ...) {
   }
 
   # Set information
-  invisible(dataset$setinfo(name = name, info = info))
+  return(invisible(dataset$setinfo(name = name, info = info)))
 }
 
 #' @name lgb.Dataset.set.categorical
@@ -1106,7 +1116,7 @@ lgb.Dataset.set.categorical <- function(dataset, categorical_feature) {
   }
 
   # Set categoricals
-  invisible(dataset$set_categorical_feature(categorical_feature = categorical_feature))
+  return(invisible(dataset$set_categorical_feature(categorical_feature = categorical_feature)))
 
 }
 
@@ -1138,7 +1148,7 @@ lgb.Dataset.set.reference <- function(dataset, reference) {
   }
 
   # Set reference
-  invisible(dataset$set_reference(reference = reference))
+  return(invisible(dataset$set_reference(reference = reference)))
 }
 
 #' @name lgb.Dataset.save
@@ -1171,5 +1181,5 @@ lgb.Dataset.save <- function(dataset, fname) {
   }
 
   # Store binary
-  invisible(dataset$save_binary(fname = fname))
+  return(invisible(dataset$save_binary(fname = fname)))
 }

R-package/R/lgb.Predictor.R

@@ -23,6 +23,8 @@ Predictor <- R6::R6Class(
 
       }
 
+      return(invisible(NULL))
+
     },
 
     # Initialize will create a starter model
@@ -59,17 +61,21 @@ Predictor <- R6::R6Class(
       class(handle) <- "lgb.Booster.handle"
       private$handle <- handle
 
+      return(invisible(NULL))
+
     },
 
     # Get current iteration
     current_iter = function() {
 
       cur_iter <- 0L
+      return(
         lgb.call(
           fun_name = "LGBM_BoosterGetCurrentIteration_R"
           , ret = cur_iter
           , private$handle
         )
+      )
 
     },
 

R-package/R/lgb.cv.R

@@ -9,10 +9,11 @@ CVBooster <- R6::R6Class(
     boosters = list(),
     initialize = function(x) {
       self$boosters <- x
+      return(invisible(NULL))
     },
     reset_parameter = function(new_params) {
       for (x in boosters) { x$reset_parameter(new_params) }
-      self
+      return(invisible(self))
     }
   )
 )
@@ -563,7 +564,7 @@ lgb.stratified.folds <- function(y, k = 10L) {
 
   out <- split(seq(along = y), foldVector)
   names(out) <- NULL
-  out
+  return(out)
 }
 
 lgb.merge.cv.result <- function(msg, showsd = TRUE) {
@@ -615,9 +616,11 @@ lgb.merge.cv.result <- function(msg, showsd = TRUE) {
   }
 
   # Return errors
+  return(
     list(
       eval_list = ret_eval
       , eval_err_list = ret_eval_err
     )
+  )
 
 }

R-package/R/lgb.interprete.R

@@ -137,10 +137,12 @@ single.tree.interprete <- function(tree_dt,
     , current_value = leaf_dt[["leaf_value"]]
   )
 
+  return(
     data.table::data.table(
       Feature = feature_seq
       , Contribution = diff.default(value_seq)
     )
+  )
 
 }
 

R-package/R/lgb.plot.importance.R

@@ -91,6 +91,6 @@ lgb.plot.importance <- function(tree_imp,
                , las = 1L
            )]
 
-  invisible(tree_imp)
+  return(invisible(tree_imp))
 
 }

R-package/R/lgb.plot.interpretation.R

@@ -124,6 +124,7 @@ lgb.plot.interpretation <- function(tree_interpretation_dt,
 
     }
   }
+  return(invisible(NULL))
 }
 
 #' @importFrom graphics barplot

R-package/R/metrics.R

@@ -7,7 +7,8 @@
 #          are returned from the C++ side. For example, if you use `metric = "mse"` in your code,
 #          the metric name `"l2"` will be returned.
 .METRICS_HIGHER_BETTER <- function() {
-    return(c(
+    return(
+        c(
             "l1" = FALSE
             , "l2" = FALSE
             , "mape" = FALSE
@@ -31,5 +32,6 @@
             , "cross_entropy" = FALSE
             , "cross_entropy_lambda" = FALSE
             , "kullback_leibler" = FALSE
-    ))
+        )
+    )
 }

R-package/R/saveRDS.lgb.Booster.R

@@ -66,6 +66,8 @@ saveRDS.lgb.Booster <- function(object,
     # Free model from memory
     object$raw <- NA
 
+    return(invisible(NULL))
+
   } else {
 
     saveRDS(
@@ -77,6 +79,8 @@ saveRDS.lgb.Booster <- function(object,
       , refhook = refhook
     )
 
+    return(invisible(NULL))
+
   }
 
 }

R-package/R/utils.R

 lgb.is.Booster <- function(x) {
-  lgb.check.r6.class(object = x, name = "lgb.Booster")
+  return(lgb.check.r6.class(object = x, name = "lgb.Booster"))
 }
 
 lgb.is.Dataset <- function(x) {
-  lgb.check.r6.class(object = x, name = "lgb.Dataset")
+  return(lgb.check.r6.class(object = x, name = "lgb.Dataset"))
 }
 
 lgb.null.handle <- function() {
@@ -15,7 +15,7 @@ lgb.null.handle <- function() {
 }
 
 lgb.is.null.handle <- function(x) {
-  is.null(x) || is.na(x)
+  return(is.null(x) || is.na(x))
 }
 
 lgb.encode.char <- function(arr, len) {
@@ -54,6 +54,9 @@ lgb.last_error <- function() {
   }
 
   stop("api error: ", lgb.encode.char(arr = err_msg, len = act_len))
+
+  return(invisible(NULL))
+
 }
 
 lgb.call <- function(fun_name, ret, ...) {
@@ -232,14 +235,14 @@ lgb.c_str <- function(x) {
 
   ret <- charToRaw(as.character(x))
   ret <- c(ret, as.raw(0L))
-  ret
+  return(ret)
 
 }
 
 lgb.check.r6.class <- function(object, name) {
 
   # Check for non-existence of R6 class or named class
-  all(c("R6", name) %in% class(object))
+  return(all(c("R6", name) %in% class(object)))
 
 }
 

build_r.R

@@ -53,6 +53,7 @@ install_libs_content <- .replace_flag("use_msys2", USING_MSYS2, install_libs_con
   if (!all(res)) {
     stop("Copying files failed!")
   }
+  return(invisible(NULL))
 }
 
 # system() will not raise an R exception if the process called