From 7586614b284d431a72d3d1f9a1d7a82ec47e05c9 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Tue, 21 May 2024 14:43:44 +0100
Subject: [PATCH 01/10] extract helper function

---
 R/misc.R | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/R/misc.R b/R/misc.R
index e1dc44e2..236f367f 100644
--- a/R/misc.R
+++ b/R/misc.R
@@ -271,13 +271,9 @@ reshuffle_rset <- function(rset) {
     }
   }
 
-  arguments <- attributes(rset)
-  useful_arguments <- names(formals(arguments$class[[1]]))
-  useful_arguments <- arguments[useful_arguments]
-  useful_arguments <- useful_arguments[!is.na(names(useful_arguments))]
-  if (identical(useful_arguments$strata, FALSE)) {
-    useful_arguments$strata <- NULL
-  } else if (identical(useful_arguments$strata, TRUE)) {
+  rset_type <- class(rset)[[1]]
+  split_arguments <- get_split_args(rset)
+  if (identical(split_arguments$strata, TRUE)) {
     rlang::abort(
       "Cannot reshuffle this rset (`attr(rset, 'strata')` is `TRUE`, not a column identifier)",
       i = "If the original object was created with an older version of rsample, try recreating it with the newest version of the package"
@@ -285,8 +281,8 @@ reshuffle_rset <- function(rset) {
   }
 
   do.call(
-    arguments$class[[1]],
-    c(list(data = rset$splits[[1]]$data), useful_arguments)
+    rset_type,
+    c(list(data = rset$splits[[1]]$data), split_arguments)
   )
 }
 
@@ -299,6 +295,17 @@ non_random_classes <- c(
   "validation_set"
 )
 
+get_split_args <- function(rset) {
+  all_attributes <- attributes(rset)
+  args <- names(formals(all_attributes$class[[1]]))
+  split_args <- all_attributes[args]
+  split_args <- split_args[!is.na(names(split_args))]
+  if (identical(split_args$strata, FALSE)) {
+    split_args$strata <- NULL
+  }
+  split_args
+}
+
 #' Retrieve individual rsplits objects from an rset
 #'
 #' @param x The `rset` object to retrieve an rsplit from.

From 7bbc732494d11f8aaf48cf0babcf9d5b08c4247a Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Tue, 21 May 2024 14:46:58 +0100
Subject: [PATCH 02/10] `inner_split()` generic + MC methods

---
 NAMESPACE                         |  3 ++
 R/inner_split.R                   | 58 +++++++++++++++++++++++++++++++
 man/inner_split.Rd                | 28 +++++++++++++++
 tests/testthat/test-inner_split.R | 56 +++++++++++++++++++++++++++++
 4 files changed, 145 insertions(+)
 create mode 100644 R/inner_split.R
 create mode 100644 man/inner_split.Rd
 create mode 100644 tests/testthat/test-inner_split.R

diff --git a/NAMESPACE b/NAMESPACE
index 19772f54..1b4f7bfb 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -25,6 +25,8 @@ S3method(dim,initial_validation_split)
 S3method(dim,rsplit)
 S3method(get_rsplit,default)
 S3method(get_rsplit,rset)
+S3method(inner_split,grouped_mc_split)
+S3method(inner_split,mc_split)
 S3method(int_bca,bootstraps)
 S3method(int_pctl,bootstraps)
 S3method(int_t,bootstraps)
@@ -368,6 +370,7 @@ export(initial_split)
 export(initial_time_split)
 export(initial_validation_split)
 export(initial_validation_time_split)
+export(inner_split)
 export(int_bca)
 export(int_pctl)
 export(int_t)
diff --git a/R/inner_split.R b/R/inner_split.R
new file mode 100644
index 00000000..1f7bd51f
--- /dev/null
+++ b/R/inner_split.R
@@ -0,0 +1,58 @@
+#' Inner split of the analysis set for fitting a post-processor
+#' 
+#' @param x An `rsplit` object.
+#' @param split_args A list of arguments to be used for the inner split.
+#' @param ... Not currently used.
+#' @return An `rsplit` object.
+#' @keywords internal
+#' @export
+inner_split <- function(x, ...) {
+  UseMethod("inner_split")
+}
+
+# mc ---------------------------------------------------------------------
+
+#' @rdname inner_split
+#' @export
+inner_split.mc_split <- function(x, split_args, ...) {
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+  
+  split_inner <- mc_splits(
+    analysis_set, 
+    prop = split_args$prop, 
+    times = 1,
+    strata = split_args$strata, 
+    breaks = split_args$breaks, 
+    pool = split_args$pool
+  )
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  split_inner <- add_class(split_inner, class_inner)
+  split_inner
+}
+
+#' @rdname inner_split
+#' @export
+inner_split.grouped_mc_split <- function(x, split_args, ...) {
+  # FIXME update this class to `group_mc_split`
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+  
+  split_inner <- group_mc_splits(
+    analysis_set, 
+    group = split_args$group,
+    prop = split_args$prop, 
+    times = 1,
+    strata = split_args$strata, 
+    pool = split_args$pool
+  )
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  split_inner <- add_class(split_inner, class_inner)
+  split_inner
+}
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
new file mode 100644
index 00000000..b528f6aa
--- /dev/null
+++ b/man/inner_split.Rd
@@ -0,0 +1,28 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/inner_split.R
+\name{inner_split}
+\alias{inner_split}
+\alias{inner_split.mc_split}
+\alias{inner_split.grouped_mc_split}
+\title{Inner split of the analysis set for fitting a post-processor}
+\usage{
+inner_split(x, ...)
+
+\method{inner_split}{mc_split}(x, split_args, ...)
+
+\method{inner_split}{grouped_mc_split}(x, split_args, ...)
+}
+\arguments{
+\item{x}{An \code{rsplit} object.}
+
+\item{...}{Not currently used.}
+
+\item{split_args}{A list of arguments to be used for the inner split.}
+}
+\value{
+An \code{rsplit} object.
+}
+\description{
+Inner split of the analysis set for fitting a post-processor
+}
+\keyword{internal}
diff --git a/tests/testthat/test-inner_split.R b/tests/testthat/test-inner_split.R
new file mode 100644
index 00000000..8d2aeb53
--- /dev/null
+++ b/tests/testthat/test-inner_split.R
@@ -0,0 +1,56 @@
+
+# mc ---------------------------------------------------------------------
+
+test_that("mc_split", {
+  set.seed(11)
+  r_set <- mc_cv(warpbreaks)
+  split_args <- get_split_args(r_set)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split, split_args)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    isplit$data[isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+  expect_identical(
+    assessment(isplit),
+    isplit$data[isplit$out_id, ],
+    ignore_attr = "row.names"
+  )
+})
+
+test_that("group_mc_split", {
+  skip_if_not_installed("modeldata")
+
+  data(ames, package = "modeldata", envir = rlang::current_env())
+
+  set.seed(11)
+  r_set <- group_mc_cv(ames, "MS_SubClass")
+  split_args <- get_split_args(r_set)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split, split_args)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    isplit$data[isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+  expect_identical(
+    assessment(isplit),
+    isplit$data[isplit$out_id, ],
+    ignore_attr = "row.names"
+  )
+})

From c966979090cbfa5ace6ab3ce3b9823b9a80e5cd1 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Tue, 21 May 2024 14:50:47 +0100
Subject: [PATCH 03/10] add `inner_split()` method for vfold cv

---
 NAMESPACE                         |  2 ++
 R/inner_split.R                   | 60 +++++++++++++++++++++++++++++++
 man/inner_split.Rd                |  6 ++++
 tests/testthat/test-inner_split.R | 57 +++++++++++++++++++++++++++++
 4 files changed, 125 insertions(+)

diff --git a/NAMESPACE b/NAMESPACE
index 1b4f7bfb..c49fb132 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -25,8 +25,10 @@ S3method(dim,initial_validation_split)
 S3method(dim,rsplit)
 S3method(get_rsplit,default)
 S3method(get_rsplit,rset)
+S3method(inner_split,group_vfold_split)
 S3method(inner_split,grouped_mc_split)
 S3method(inner_split,mc_split)
+S3method(inner_split,vfold_split)
 S3method(int_bca,bootstraps)
 S3method(int_pctl,bootstraps)
 S3method(int_t,bootstraps)
diff --git a/R/inner_split.R b/R/inner_split.R
index 1f7bd51f..94437918 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -56,3 +56,63 @@ inner_split.grouped_mc_split <- function(x, split_args, ...) {
   split_inner <- add_class(split_inner, class_inner)
   split_inner
 }
+
+
+# vfold ------------------------------------------------------------------
+
+#' @rdname inner_split
+#' @export
+inner_split.vfold_split <- function(x, split_args, ...) {
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+  
+  # TODO should this be done outside of rsample, 
+  # in workflows or tune?
+  if (is.null(split_args$prop)) {
+    split_args$prop <- 1 - 1/split_args$v
+  }
+  # use mc_splits for a random split
+  split_inner <- mc_splits(
+    analysis_set, 
+    prop = split_args$prop, 
+    times = 1,
+    strata = split_args$strata, 
+    breaks = split_args$breaks, 
+    pool = split_args$pool
+  )
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  class(split_inner) <- c(class_inner, class(x))
+  split_inner
+}
+
+#' @rdname inner_split
+#' @export
+inner_split.group_vfold_split <- function(x, split_args, ...) {
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+
+  # TODO should this be done outside of rsample, 
+  # in workflows or tune?
+  if (is.null(split_args$prop)) {
+    split_args$prop <- 1 - 1/split_args$v
+  }
+  
+  # use group_mc_splits for a random split
+  split_inner <- group_mc_splits(
+    analysis_set, 
+    group = split_args$group,
+    prop = split_args$prop, 
+    times = 1,
+    strata = split_args$strata, 
+    pool = split_args$pool
+  )
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  class(split_inner) <- c(class_inner, class(x))
+  split_inner
+}
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
index b528f6aa..02a9cc41 100644
--- a/man/inner_split.Rd
+++ b/man/inner_split.Rd
@@ -4,6 +4,8 @@
 \alias{inner_split}
 \alias{inner_split.mc_split}
 \alias{inner_split.grouped_mc_split}
+\alias{inner_split.vfold_split}
+\alias{inner_split.group_vfold_split}
 \title{Inner split of the analysis set for fitting a post-processor}
 \usage{
 inner_split(x, ...)
@@ -11,6 +13,10 @@ inner_split(x, ...)
 \method{inner_split}{mc_split}(x, split_args, ...)
 
 \method{inner_split}{grouped_mc_split}(x, split_args, ...)
+
+\method{inner_split}{vfold_split}(x, split_args, ...)
+
+\method{inner_split}{group_vfold_split}(x, split_args, ...)
 }
 \arguments{
 \item{x}{An \code{rsplit} object.}
diff --git a/tests/testthat/test-inner_split.R b/tests/testthat/test-inner_split.R
index 8d2aeb53..6254316d 100644
--- a/tests/testthat/test-inner_split.R
+++ b/tests/testthat/test-inner_split.R
@@ -54,3 +54,60 @@ test_that("group_mc_split", {
     ignore_attr = "row.names"
   )
 })
+
+
+# vfold ------------------------------------------------------------------
+
+test_that("vfold_split", {
+  set.seed(11)
+  r_set <- vfold_cv(warpbreaks, v = 5)
+  split_args <- get_split_args(r_set)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split, split_args)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    isplit$data[isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+  expect_identical(
+    assessment(isplit),
+    isplit$data[isplit$out_id, ],
+    ignore_attr = "row.names"
+  )
+})
+
+test_that("group_vfold_split", {
+  skip_if_not_installed("modeldata")
+
+  data(ames, package = "modeldata", envir = rlang::current_env())
+
+  set.seed(11)
+  r_set <- group_vfold_cv(ames, "MS_SubClass")
+  split_args <- get_split_args(r_set)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split, split_args)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    isplit$data[isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+  expect_identical(
+    assessment(isplit),
+    isplit$data[isplit$out_id, ],
+    ignore_attr = "row.names"
+  )
+})

From d306c59e294ae7c5e363f662896c459b28ca4f51 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Tue, 21 May 2024 14:53:41 +0100
Subject: [PATCH 04/10] add `inner_split()` method for clustering cv

---
 NAMESPACE                         |  1 +
 R/inner_split.R                   | 25 +++++++++++++++++++++++++
 man/inner_split.Rd                |  3 +++
 tests/testthat/test-inner_split.R | 29 +++++++++++++++++++++++++++++
 4 files changed, 58 insertions(+)

diff --git a/NAMESPACE b/NAMESPACE
index c49fb132..fa7dee7e 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -25,6 +25,7 @@ S3method(dim,initial_validation_split)
 S3method(dim,rsplit)
 S3method(get_rsplit,default)
 S3method(get_rsplit,rset)
+S3method(inner_split,clustering_split)
 S3method(inner_split,group_vfold_split)
 S3method(inner_split,grouped_mc_split)
 S3method(inner_split,mc_split)
diff --git a/R/inner_split.R b/R/inner_split.R
index 94437918..59857c41 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -116,3 +116,28 @@ inner_split.group_vfold_split <- function(x, split_args, ...) {
   class(split_inner) <- c(class_inner, class(x))
   split_inner
 }
+
+# clustering -------------------------------------------------------------
+
+#' @rdname inner_split
+#' @export
+inner_split.clustering_split <- function(x, split_args, ...) {
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+  
+  # TODO: reduce the number of clusters by 1 in tune?
+  split_inner <- clustering_cv(
+    analysis_set, 
+    vars = split_args$vars,
+    v = split_args$v, 
+    repeats = 1,
+    distance_function = split_args$distance_function,
+    cluster_function = split_args$cluster_function
+  )
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  class(split_inner) <- c(class_inner, class(x))
+  split_inner
+}
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
index 02a9cc41..814f2d4b 100644
--- a/man/inner_split.Rd
+++ b/man/inner_split.Rd
@@ -6,6 +6,7 @@
 \alias{inner_split.grouped_mc_split}
 \alias{inner_split.vfold_split}
 \alias{inner_split.group_vfold_split}
+\alias{inner_split.clustering_split}
 \title{Inner split of the analysis set for fitting a post-processor}
 \usage{
 inner_split(x, ...)
@@ -17,6 +18,8 @@ inner_split(x, ...)
 \method{inner_split}{vfold_split}(x, split_args, ...)
 
 \method{inner_split}{group_vfold_split}(x, split_args, ...)
+
+\method{inner_split}{clustering_split}(x, split_args, ...)
 }
 \arguments{
 \item{x}{An \code{rsplit} object.}
diff --git a/tests/testthat/test-inner_split.R b/tests/testthat/test-inner_split.R
index 6254316d..839ca9e2 100644
--- a/tests/testthat/test-inner_split.R
+++ b/tests/testthat/test-inner_split.R
@@ -111,3 +111,32 @@ test_that("group_vfold_split", {
     ignore_attr = "row.names"
   )
 })
+
+
+# clustering -------------------------------------------------------------
+
+test_that("clustering_split", {
+  set.seed(11)
+  r_set <- clustering_cv(warpbreaks, vars = breaks, v = 5)
+  split_args <- get_split_args(r_set)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split, split_args)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    isplit$data[isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+  expect_identical(
+    assessment(isplit),
+    isplit$data[-isplit$in_id, ],
+    ignore_attr = "row.names"
+  )
+})
+

From d668b7533699ef4d040bea3f201d395b57906bc4 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Tue, 21 May 2024 14:55:31 +0100
Subject: [PATCH 05/10] add `inner_split()` method for apparent split

---
 NAMESPACE                         |  1 +
 R/inner_split.R                   | 18 ++++++++++++++++++
 man/inner_split.Rd                |  3 +++
 tests/testthat/test-inner_split.R | 23 +++++++++++++++++++++++
 4 files changed, 45 insertions(+)

diff --git a/NAMESPACE b/NAMESPACE
index fa7dee7e..9b01b7e7 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -25,6 +25,7 @@ S3method(dim,initial_validation_split)
 S3method(dim,rsplit)
 S3method(get_rsplit,default)
 S3method(get_rsplit,rset)
+S3method(inner_split,apparent_split)
 S3method(inner_split,clustering_split)
 S3method(inner_split,group_vfold_split)
 S3method(inner_split,grouped_mc_split)
diff --git a/R/inner_split.R b/R/inner_split.R
index 59857c41..02c9482c 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -141,3 +141,21 @@ inner_split.clustering_split <- function(x, split_args, ...) {
   class(split_inner) <- c(class_inner, class(x))
   split_inner
 }
+
+
+# apparent ---------------------------------------------------------------
+
+#' @rdname inner_split
+#' @export
+inner_split.apparent_split <- function(x, ...) {
+  check_dots_empty() 
+
+  analysis_set <- analysis(x)
+  
+  split_inner <- apparent(analysis_set)
+  split_inner <- split_inner$splits[[1]]
+
+  class_inner <- paste0(class(x)[1], "_inner")
+  class(split_inner) <- c(class_inner, class(x))
+  split_inner
+}
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
index 814f2d4b..4cbe9bef 100644
--- a/man/inner_split.Rd
+++ b/man/inner_split.Rd
@@ -7,6 +7,7 @@
 \alias{inner_split.vfold_split}
 \alias{inner_split.group_vfold_split}
 \alias{inner_split.clustering_split}
+\alias{inner_split.apparent_split}
 \title{Inner split of the analysis set for fitting a post-processor}
 \usage{
 inner_split(x, ...)
@@ -20,6 +21,8 @@ inner_split(x, ...)
 \method{inner_split}{group_vfold_split}(x, split_args, ...)
 
 \method{inner_split}{clustering_split}(x, split_args, ...)
+
+\method{inner_split}{apparent_split}(x, ...)
 }
 \arguments{
 \item{x}{An \code{rsplit} object.}
diff --git a/tests/testthat/test-inner_split.R b/tests/testthat/test-inner_split.R
index 839ca9e2..8c7ed21e 100644
--- a/tests/testthat/test-inner_split.R
+++ b/tests/testthat/test-inner_split.R
@@ -140,3 +140,26 @@ test_that("clustering_split", {
   )
 })
 
+# apparent ---------------------------------------------------------------
+
+test_that("apparent_split", {
+  set.seed(11)
+  r_set <- apparent(warpbreaks)
+  r_split <- get_rsplit(r_set, 1)
+
+  isplit <- inner_split(r_split)
+
+  expect_identical(
+    isplit$data,
+    analysis(r_split)
+  )
+
+  expect_identical(
+    analysis(isplit),
+    analysis(r_split)
+  )
+  expect_identical(
+    assessment(isplit),
+    analysis(r_split)
+  )
+})

From 893b071a9bf85f756375fa1a95c643302b55fe5b Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Wed, 22 May 2024 21:06:16 +0100
Subject: [PATCH 06/10] a little metaprogramming

to force errors for usused arguments if necessary, i.e. not swallow them silently.
---
 R/inner_split.R | 59 ++++++++++++++++++-------------------------------
 1 file changed, 22 insertions(+), 37 deletions(-)

diff --git a/R/inner_split.R b/R/inner_split.R
index 02c9482c..d20cce83 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -18,14 +18,10 @@ inner_split.mc_split <- function(x, split_args, ...) {
   check_dots_empty() 
 
   analysis_set <- analysis(x)
-  
-  split_inner <- mc_splits(
-    analysis_set, 
-    prop = split_args$prop, 
-    times = 1,
-    strata = split_args$strata, 
-    breaks = split_args$breaks, 
-    pool = split_args$pool
+
+  split_args$times <- 1
+  split_inner <- rlang::inject(
+    mc_splits(analysis_set, !!!split_args)
   )
   split_inner <- split_inner$splits[[1]]
 
@@ -41,14 +37,10 @@ inner_split.grouped_mc_split <- function(x, split_args, ...) {
   check_dots_empty() 
 
   analysis_set <- analysis(x)
-  
-  split_inner <- group_mc_splits(
-    analysis_set, 
-    group = split_args$group,
-    prop = split_args$prop, 
-    times = 1,
-    strata = split_args$strata, 
-    pool = split_args$pool
+
+  split_args$times <- 1
+  split_inner <- rlang::inject(
+    group_mc_splits(analysis_set, !!!split_args)
   )
   split_inner <- split_inner$splits[[1]]
 
@@ -73,13 +65,11 @@ inner_split.vfold_split <- function(x, split_args, ...) {
     split_args$prop <- 1 - 1/split_args$v
   }
   # use mc_splits for a random split
-  split_inner <- mc_splits(
-    analysis_set, 
-    prop = split_args$prop, 
-    times = 1,
-    strata = split_args$strata, 
-    breaks = split_args$breaks, 
-    pool = split_args$pool
+  split_args$times <- 1
+  split_args$v <- NULL
+  split_args$repeats <- NULL
+  split_inner <- rlang::inject(
+    mc_splits(analysis_set, !!!split_args)
   )
   split_inner <- split_inner$splits[[1]]
 
@@ -102,13 +92,12 @@ inner_split.group_vfold_split <- function(x, split_args, ...) {
   }
   
   # use group_mc_splits for a random split
-  split_inner <- group_mc_splits(
-    analysis_set, 
-    group = split_args$group,
-    prop = split_args$prop, 
-    times = 1,
-    strata = split_args$strata, 
-    pool = split_args$pool
+  split_args$times <- 1
+  split_args$v <- NULL
+  split_args$repeats <- NULL
+  split_args$balance <- NULL
+  split_inner <- rlang::inject(
+    group_mc_splits(analysis_set, !!!split_args)
   )
   split_inner <- split_inner$splits[[1]]
 
@@ -127,13 +116,9 @@ inner_split.clustering_split <- function(x, split_args, ...) {
   analysis_set <- analysis(x)
   
   # TODO: reduce the number of clusters by 1 in tune?
-  split_inner <- clustering_cv(
-    analysis_set, 
-    vars = split_args$vars,
-    v = split_args$v, 
-    repeats = 1,
-    distance_function = split_args$distance_function,
-    cluster_function = split_args$cluster_function
+  split_args$repeats <- 1
+  split_inner <- rlang::inject(
+    clustering_cv(analysis_set, !!!split_args)
   )
   split_inner <- split_inner$splits[[1]]
 

From f42e8fdbe5fc9bcf64082e585ed1464971c07017 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Thu, 23 May 2024 10:51:31 +0100
Subject: [PATCH 07/10] export renamed helper for use in tune

---
 NAMESPACE                         |  1 +
 R/misc.R                          |  9 +++++++--
 man/dot-get_split_args.Rd         | 18 ++++++++++++++++++
 tests/testthat/test-inner_split.R | 10 +++++-----
 4 files changed, 31 insertions(+), 7 deletions(-)
 create mode 100644 man/dot-get_split_args.Rd

diff --git a/NAMESPACE b/NAMESPACE
index 9b01b7e7..55832fe4 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -349,6 +349,7 @@ S3method(vec_restore,validation_split)
 S3method(vec_restore,validation_time_split)
 S3method(vec_restore,vfold_cv)
 export(.get_fingerprint)
+export(.get_split_args)
 export(add_resample_id)
 export(all_of)
 export(analysis)
diff --git a/R/misc.R b/R/misc.R
index 236f367f..3b1aa7bf 100644
--- a/R/misc.R
+++ b/R/misc.R
@@ -272,7 +272,7 @@ reshuffle_rset <- function(rset) {
   }
 
   rset_type <- class(rset)[[1]]
-  split_arguments <- get_split_args(rset)
+  split_arguments <- .get_split_args(rset)
   if (identical(split_arguments$strata, TRUE)) {
     rlang::abort(
       "Cannot reshuffle this rset (`attr(rset, 'strata')` is `TRUE`, not a column identifier)",
@@ -295,7 +295,12 @@ non_random_classes <- c(
   "validation_set"
 )
 
-get_split_args <- function(rset) {
+#' Get the split arguments from an rset
+#' @param rset An `rset` object.
+#' @return A list of arguments used to create the rset.
+#' @keywords internal
+#' @export
+.get_split_args <- function(rset) {
   all_attributes <- attributes(rset)
   args <- names(formals(all_attributes$class[[1]]))
   split_args <- all_attributes[args]
diff --git a/man/dot-get_split_args.Rd b/man/dot-get_split_args.Rd
new file mode 100644
index 00000000..c4bccaaf
--- /dev/null
+++ b/man/dot-get_split_args.Rd
@@ -0,0 +1,18 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/misc.R
+\name{.get_split_args}
+\alias{.get_split_args}
+\title{Get the split arguments from an rset}
+\usage{
+.get_split_args(rset)
+}
+\arguments{
+\item{rset}{An \code{rset} object.}
+}
+\value{
+A list of arguments used to create the rset.
+}
+\description{
+Get the split arguments from an rset
+}
+\keyword{internal}
diff --git a/tests/testthat/test-inner_split.R b/tests/testthat/test-inner_split.R
index 8c7ed21e..61153f2c 100644
--- a/tests/testthat/test-inner_split.R
+++ b/tests/testthat/test-inner_split.R
@@ -4,7 +4,7 @@
 test_that("mc_split", {
   set.seed(11)
   r_set <- mc_cv(warpbreaks)
-  split_args <- get_split_args(r_set)
+  split_args <- .get_split_args(r_set)
   r_split <- get_rsplit(r_set, 1)
 
   isplit <- inner_split(r_split, split_args)
@@ -33,7 +33,7 @@ test_that("group_mc_split", {
 
   set.seed(11)
   r_set <- group_mc_cv(ames, "MS_SubClass")
-  split_args <- get_split_args(r_set)
+  split_args <- .get_split_args(r_set)
   r_split <- get_rsplit(r_set, 1)
 
   isplit <- inner_split(r_split, split_args)
@@ -61,7 +61,7 @@ test_that("group_mc_split", {
 test_that("vfold_split", {
   set.seed(11)
   r_set <- vfold_cv(warpbreaks, v = 5)
-  split_args <- get_split_args(r_set)
+  split_args <- .get_split_args(r_set)
   r_split <- get_rsplit(r_set, 1)
 
   isplit <- inner_split(r_split, split_args)
@@ -90,7 +90,7 @@ test_that("group_vfold_split", {
 
   set.seed(11)
   r_set <- group_vfold_cv(ames, "MS_SubClass")
-  split_args <- get_split_args(r_set)
+  split_args <- .get_split_args(r_set)
   r_split <- get_rsplit(r_set, 1)
 
   isplit <- inner_split(r_split, split_args)
@@ -118,7 +118,7 @@ test_that("group_vfold_split", {
 test_that("clustering_split", {
   set.seed(11)
   r_set <- clustering_cv(warpbreaks, vars = breaks, v = 5)
-  split_args <- get_split_args(r_set)
+  split_args <- .get_split_args(r_set)
   r_split <- get_rsplit(r_set, 1)
 
   isplit <- inner_split(r_split, split_args)

From 171c83fcbad91f818cb19a8bfe858ad59013d9c4 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Thu, 23 May 2024 10:57:09 +0100
Subject: [PATCH 08/10] update to new class for grouped MC

---
 NAMESPACE          | 2 +-
 R/inner_split.R    | 3 +--
 man/inner_split.Rd | 4 ++--
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index 55832fe4..d01b9f3f 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -27,8 +27,8 @@ S3method(get_rsplit,default)
 S3method(get_rsplit,rset)
 S3method(inner_split,apparent_split)
 S3method(inner_split,clustering_split)
+S3method(inner_split,group_mc_split)
 S3method(inner_split,group_vfold_split)
-S3method(inner_split,grouped_mc_split)
 S3method(inner_split,mc_split)
 S3method(inner_split,vfold_split)
 S3method(int_bca,bootstraps)
diff --git a/R/inner_split.R b/R/inner_split.R
index d20cce83..6b749348 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -32,8 +32,7 @@ inner_split.mc_split <- function(x, split_args, ...) {
 
 #' @rdname inner_split
 #' @export
-inner_split.grouped_mc_split <- function(x, split_args, ...) {
-  # FIXME update this class to `group_mc_split`
+inner_split.group_mc_split <- function(x, split_args, ...) {
   check_dots_empty() 
 
   analysis_set <- analysis(x)
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
index 4cbe9bef..81e89391 100644
--- a/man/inner_split.Rd
+++ b/man/inner_split.Rd
@@ -3,7 +3,7 @@
 \name{inner_split}
 \alias{inner_split}
 \alias{inner_split.mc_split}
-\alias{inner_split.grouped_mc_split}
+\alias{inner_split.group_mc_split}
 \alias{inner_split.vfold_split}
 \alias{inner_split.group_vfold_split}
 \alias{inner_split.clustering_split}
@@ -14,7 +14,7 @@ inner_split(x, ...)
 
 \method{inner_split}{mc_split}(x, split_args, ...)
 
-\method{inner_split}{grouped_mc_split}(x, split_args, ...)
+\method{inner_split}{group_mc_split}(x, split_args, ...)
 
 \method{inner_split}{vfold_split}(x, split_args, ...)
 

From 3a6030aff9e60522e98379990289f43b98f95389 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Thu, 23 May 2024 10:57:47 +0100
Subject: [PATCH 09/10] update NEWS

---
 NEWS.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 9404b5e8..75785b90 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # rsample (development version)
 
+* The new `inner_split()` function and its methods for various resamples is for usage in tune to create a inner resample of the analysis set to fit the preprocessor and model on one part and the post-processor on the other part (#483).
+
 ## Bug fixes
 
 * `vfold_cv()` now utilizes the `breaks` argument correctly for repeated cross-validation (@ZWael, #471).

From f915a34e002e7b1e59b29e9b991ab054e79917f1 Mon Sep 17 00:00:00 2001
From: Hannah Frick <hannah@posit.co>
Date: Thu, 23 May 2024 11:27:16 +0100
Subject: [PATCH 10/10]  add more documentation

---
 R/inner_split.R    | 14 ++++++++++++++
 man/inner_split.Rd | 16 ++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/R/inner_split.R b/R/inner_split.R
index 6b749348..6cd442df 100644
--- a/R/inner_split.R
+++ b/R/inner_split.R
@@ -4,6 +4,20 @@
 #' @param split_args A list of arguments to be used for the inner split.
 #' @param ... Not currently used.
 #' @return An `rsplit` object.
+#' @details
+#' `rsplit` objects live most commonly inside of an `rset` object. The 
+#' `split_args` argument can be the output of [.get_split_args()] on that 
+#' corresponding `rset` object, even if some of the arguments used to creat the 
+#' `rset` object are not needed for the inner split. 
+#' * For `mc_split` and `group_mc_split` objects, `inner_split()` will ignore 
+#' `split_args$times`.
+#' * For `vfold_split` and `group_vfold_split` objects, it will ignore 
+#' `split_args$times` and `split_args$repeats`. `split_args$v` will be used to 
+#' set `split_args$prop` to `1 - 1/v` if `prop` is not already set and otherwise 
+#' ignored. The method 
+#' for `group_vfold_split` will always use `split_args$balance = NULL`.
+#' * For `clustering_split` objects, it will ignore `split_args$repeats`.
+#'  
 #' @keywords internal
 #' @export
 inner_split <- function(x, ...) {
diff --git a/man/inner_split.Rd b/man/inner_split.Rd
index 81e89391..b4114927 100644
--- a/man/inner_split.Rd
+++ b/man/inner_split.Rd
@@ -37,4 +37,20 @@ An \code{rsplit} object.
 \description{
 Inner split of the analysis set for fitting a post-processor
 }
+\details{
+\code{rsplit} objects live most commonly inside of an \code{rset} object. The
+\code{split_args} argument can be the output of \code{\link[=.get_split_args]{.get_split_args()}} on that
+corresponding \code{rset} object, even if some of the arguments used to creat the
+\code{rset} object are not needed for the inner split.
+\itemize{
+\item For \code{mc_split} and \code{group_mc_split} objects, \code{inner_split()} will ignore
+\code{split_args$times}.
+\item For \code{vfold_split} and \code{group_vfold_split} objects, it will ignore
+\code{split_args$times} and \code{split_args$repeats}. \code{split_args$v} will be used to
+set \code{split_args$prop} to \code{1 - 1/v} if \code{prop} is not already set and otherwise
+ignored. The method
+for \code{group_vfold_split} will always use \code{split_args$balance = NULL}.
+\item For \code{clustering_split} objects, it will ignore \code{split_args$repeats}.
+}
+}
 \keyword{internal}