From b2c7f09b0a095ba0c0f3141a5734bf958d23b86a Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Sat, 29 Jun 2024 14:08:43 +0200
Subject: [PATCH] Fix underflow in Printer::printList

Analogous to 9b88bf8adf7 / three commits back
---
 src/libexpr/print.cc                                  |  6 +++++-
 .../lang/eval-fail-nested-list-items.err.exp          |  9 +++++++++
 tests/functional/lang/eval-fail-nested-list-items.nix | 11 +++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tests/functional/lang/eval-fail-nested-list-items.err.exp
 create mode 100644 tests/functional/lang/eval-fail-nested-list-items.nix

diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 74aa52d48..2f377e588 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -405,11 +405,14 @@ private:
             output << "[";
             auto listItems = v.listItems();
             auto prettyPrint = shouldPrettyPrintList(listItems);
+
+            size_t currentListItemsPrinted = 0;
+
             for (auto elem : listItems) {
                 printSpace(prettyPrint);
 
                 if (totalListItemsPrinted >= options.maxListItems) {
-                    printElided(listItems.size() - totalListItemsPrinted, "item", "items");
+                    printElided(listItems.size() - currentListItemsPrinted, "item", "items");
                     break;
                 }
 
@@ -419,6 +422,7 @@ private:
                     printNullptr();
                 }
                 totalListItemsPrinted++;
+                currentListItemsPrinted++;
             }
 
             decreaseIndent();
diff --git a/tests/functional/lang/eval-fail-nested-list-items.err.exp b/tests/functional/lang/eval-fail-nested-list-items.err.exp
new file mode 100644
index 000000000..90d439061
--- /dev/null
+++ b/tests/functional/lang/eval-fail-nested-list-items.err.exp
@@ -0,0 +1,9 @@
+error:
+       … while evaluating a path segment
+         at /pwd/lang/eval-fail-nested-list-items.nix:11:6:
+           10|
+           11| "" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)
+             |      ^
+           12|
+
+       error: cannot coerce a list to a string: [ [ 1 2 3 4 5 6 7 8 ] [ 1 «3 items elided» ] ]
diff --git a/tests/functional/lang/eval-fail-nested-list-items.nix b/tests/functional/lang/eval-fail-nested-list-items.nix
new file mode 100644
index 000000000..af45b1dd4
--- /dev/null
+++ b/tests/functional/lang/eval-fail-nested-list-items.nix
@@ -0,0 +1,11 @@
+# This reproduces https://github.com/NixOS/nix/issues/10993, for lists
+# $ nix run nix/2.23.1 -- eval --expr '"" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)'
+# error:
+#        … while evaluating a path segment
+#          at «string»:1:6:
+#             1| "" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)
+#              |      ^
+#
+#        error: cannot coerce a list to a string: [ [ 1 2 3 4 5 6 7 8 ] [ 1 «4294967290 items elided» ] ]
+
+"" + (let v = [ [ 1 2 3 4 5 6 7 8 ] [1 2 3 4]]; in builtins.deepSeq v v)