From 55ccb40083635dbb0f1df36dc2e1a0dfc5f45dbe Mon Sep 17 00:00:00 2001
From: Kevin Robert Stravers <kevin@stravers.net>
Date: Mon, 2 Sep 2024 15:11:06 -0400
Subject: [PATCH] nix repl: Print which variables are just loaded

When we run `nix repl nixpkgs` we get "Added 6 variables". This is not
useful as it doesn't tell us which variables the flake has exported to
our global repl scope.

This patch prints the name of each variable that was just loaded. We
currently cap printing to 10 variables in order to avoid excessive
prints.

Github issue: 11404
---
 src/libcmd/repl.cc       | 13 +++++++++++++
 tests/functional/repl.sh |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/src/libcmd/repl.cc b/src/libcmd/repl.cc
index 63f6c1bdd0db..0aed7eda8653 100644
--- a/src/libcmd/repl.cc
+++ b/src/libcmd/repl.cc
@@ -790,6 +790,19 @@ void NixRepl::addAttrsToScope(Value & attrs)
     staticEnv->sort();
     staticEnv->deduplicate();
     notice("Added %1% variables.", attrs.attrs()->size());
+
+    const int max_print = 10;
+    int count = 0;
+    for (auto & i : *attrs.attrs()) {
+        count += 1;
+        if (count > max_print) {
+            notice("... And %1% other variables", attrs.attrs()->size() - max_print);
+            break;
+        }
+
+        std::string_view name = state->symbols[i.name];
+        notice("- %1%", name);
+    }
 }
 
 
diff --git a/tests/functional/repl.sh b/tests/functional/repl.sh
index 706e0f5dba98..d416a05e905c 100755
--- a/tests/functional/repl.sh
+++ b/tests/functional/repl.sh
@@ -302,6 +302,8 @@ runRepl () {
       -e "s@$testDirNoUnderscores@/path/to/tests/functional@g" \
       -e "s@$nixVersion@<nix version>@g" \
       -e "s@Added [0-9]* variables@Added <number omitted> variables@g" \
+      -e '/^- /d' \
+      -e '/\.\.\. And [0-9]* other variables/d' \
     | grep -vF $'warning: you don\'t have Internet access; disabling some network-dependent features' \
     ;
 }