From d77cc689ec8e87d8146ab575c4b44514308039da Mon Sep 17 00:00:00 2001
From: Tomasz Kalinowski <tomasz@posit.co>
Date: Wed, 13 Nov 2024 09:29:37 -0500
Subject: [PATCH] implement `ChildrenOverflow` for >100 children

---
 R/ark-variables-methods.R             | 43 ++++++++++++++++-----------
 R/zzz.R                               | 11 ++++---
 inst/python/rpytools/ark_variables.py | 33 ++++++++++++++++++++
 3 files changed, 65 insertions(+), 22 deletions(-)
 create mode 100644 inst/python/rpytools/ark_variables.py

diff --git a/R/ark-variables-methods.R b/R/ark-variables-methods.R
index 066160f2e..4db8c949e 100644
--- a/R/ark-variables-methods.R
+++ b/R/ark-variables-methods.R
@@ -17,7 +17,7 @@ ark_positron_variable_display_type.python.builtin.object <- function(x, ..., inc
   i <- .globals$get_positron_variable_inspector(x)
   out <-  i$get_display_type()
 
-  if(startsWith(class(x)[1], "python.builtin."))
+  if (startsWith(class(x)[1], "python.builtin.")) # display convert value?
     out <- paste("python", out)
 
   out
@@ -44,17 +44,15 @@ ark_positron_variable_get_children.python.builtin.object <- function(x, ...) {
 
   get_keys_and_children <- .globals$ark_variable_get_keys_and_children
   if (is.null(get_keys_and_children)) {
-    get_keys_and_children <- .globals$ark_variable_get_keys_and_children <- py_eval(
-      "lambda i: zip(*((str(key), i.get_child(key)) for key in i.get_children()))",
-      convert = FALSE
-    )
+    get_keys_and_children <- .globals$ark_variable_get_keys_and_children <-
+      import("rpytools.ark_variables", convert = FALSE)$get_keys_and_children
   }
 
   keys_and_children <- iterate(get_keys_and_children(i), simplify = FALSE)
-  out <- iterate(keys_and_children[[2L]], simplify = FALSE)
-  names(out) <- as.character(py_to_r(keys_and_children[[1L]]))
+  children <- iterate(keys_and_children[[2L]], simplify = FALSE)
+  names(children) <- as.character(py_to_r(keys_and_children[[1L]]))
 
-  out
+  children
 }
 
 #' @param index An integer > 1, representing the index position of the child in the
@@ -70,16 +68,25 @@ ark_positron_variable_get_child_at.python.builtin.object <- function(x, ..., nam
   i <- .globals$get_positron_variable_inspector(x)
   get_child <- .globals$ark_variable_get_child
   if (is.null(get_child)) {
-    get_child <- .globals$ark_variable_get_child <- py_run_string(
-      local = TRUE, convert = FALSE, "
-def new_get_child():
-  from itertools import islice
-  def get_child(inspector, index):
-    key = next(islice(inspector.get_children(), index-1, None))
-    return inspector.get_child(key)
-  return get_child
-")$new_get_child()
+    get_child <- .globals$ark_variable_get_child <-
+      import("rpytools.ark_variables", convert = FALSE)$get_child
+    }
+
+    get_child(i, index)
   }
 
-  get_child(i, index)
+
+ark_positron_variable_display_type.rpytools.ark_variables.ChildrenOverflow <- function(x, ..., include_length = TRUE) {
+  ""
+}
+ark_positron_variable_kind.rpytools.ark_variables.ChildrenOverflow <- function(x, ...) {
+  "empty" # other? collection? map? lazy?
+}
+
+ark_positron_variable_display_value.rpytools.ark_variables.ChildrenOverflow <- function(x, ..., width = getOption("width")) {
+  paste(py_to_r(x$n_remaining), "more values")
+}
+
+ark_positron_variable_has_children.rpytools.ark_variables.ChildrenOverflow <- function(x, ...) {
+  FALSE
 }
diff --git a/R/zzz.R b/R/zzz.R
index a4befd2c2..bbdfe1858 100644
--- a/R/zzz.R
+++ b/R/zzz.R
@@ -84,10 +84,13 @@
         "ark_positron_variable_get_child_at",
         "ark_positron_variable_get_children"
       )) {
-        method_sym <- as.name(paste0(method_name, ".python.builtin.object"))
-        .ark.register_method(
-          method_name, "python.builtin.object",
-          call(":::", quote(reticulate), method_sym))
+        for (class_name in c("python.builtin.object",
+                             "rpytools.ark_variables.ChildrenOverflow")) {
+          method <- get0(paste0(method_name, ".", class_name))
+          if (!is.null(method)) {
+            .ark.register_method(method_name, class_name, method)
+          }
+        }
       }
     })
   }
diff --git a/inst/python/rpytools/ark_variables.py b/inst/python/rpytools/ark_variables.py
new file mode 100644
index 000000000..180c8c1eb
--- /dev/null
+++ b/inst/python/rpytools/ark_variables.py
@@ -0,0 +1,33 @@
+from itertools import islice
+
+MAX_DISPLAY = 100
+
+def get_keys_and_children(inspector):
+    keys, values = [], []
+    keys_iterator = iter(inspector.get_children())
+    # positron frontend only displays the first 100 items, then the length of the rest.
+    try:
+        for _ in range(MAX_DISPLAY):
+            key = next(keys_iterator)
+            keys.append(str(key))
+            values.append(inspector.get_child(key))
+    except StopIteration:
+        return keys, values
+
+    n_remaining = 0
+    for n_remaining, _ in enumerate(keys_iterator, 1):
+        pass
+    if n_remaining > 0:
+        keys.append("[[...]]")
+        values.append(ChildrenOverflow(n_remaining))
+
+    return keys, values
+
+
+def get_child(inspector, index):
+    key = next(islice(inspector.get_children(), index - 1, None))
+    return inspector.get_child(key)
+
+class ChildrenOverflow:
+    def __init__(self, n_remaining):
+        self.n_remaining = n_remaining