[R-package] move all examples to dontrun() to fix R CMD CHECK notes (#3270)

* Move all examples to dontrun

* update docs

* fix nested dontrun

* remove :: in examples

* run_dontrun in pkgdown
Co-authored-by: Nikita Titov <nekit94-08@mail.ru>

R-package/man/readRDS.lgb.Booster.Rd

@@ -18,7 +18,7 @@ readRDS.lgb.Booster(file = "", refhook = NULL)
 Attempts to load a model stored in a \code{.rds} file, using \code{\link[base]{readRDS}}
 }
 \examples{
-\donttest{
+\dontrun{
 library(lightgbm)
 data(agaricus.train, package = "lightgbm")
 train <- agaricus.train

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

@@ -42,7 +42,7 @@ Attempts to save a model using RDS. Has an additional parameter (\code{raw})
              which decides whether to save the raw model or not.
 }
 \examples{
-\donttest{
+\dontrun{
 library(lightgbm)
 data(agaricus.train, package = "lightgbm")
 train <- agaricus.train

R-package/man/setinfo.Rd

@@ -38,6 +38,7 @@ The \code{name} field can be one of the following:
 }
 }
 \examples{
+\dontrun{
 data(agaricus.train, package = "lightgbm")
 train <- agaricus.train
 dtrain <- lgb.Dataset(train$data, label = train$label)
@@ -48,5 +49,5 @@ lightgbm::setinfo(dtrain, "label", 1 - labels)
 
 labels2 <- lightgbm::getinfo(dtrain, "label")
 stopifnot(all.equal(labels2, 1 - labels))
-
+}
 }

R-package/man/slice.Rd

@@ -24,6 +24,7 @@ Get a new \code{lgb.Dataset} containing the specified rows of
              original \code{lgb.Dataset} object
 }
 \examples{
+\dontrun{
 data(agaricus.train, package = "lightgbm")
 train <- agaricus.train
 dtrain <- lgb.Dataset(train$data, label = train$label)
@@ -31,5 +32,5 @@ dtrain <- lgb.Dataset(train$data, label = train$label)
 dsub <- lightgbm::slice(dtrain, seq_len(42L))
 lgb.Dataset.construct(dsub)
 labels <- lightgbm::getinfo(dsub, "label")
-
+}
 }

docs/conf.py

@@ -247,7 +247,7 @@ def generate_r_docs(app):
             , install = FALSE \
             , devel = FALSE \
             , examples = TRUE \
-            , run_dont_run = FALSE \
+            , run_dont_run = TRUE \
             , seed = 42L \
             , preview = FALSE \
             , new_process = TRUE \