From d97d311ddfbb656bc4ccd1e81f9059d0ddea8c8d Mon Sep 17 00:00:00 2001
From: Graham Christensen <graham@grahamc.com>
Date: Thu, 24 Apr 2025 20:10:54 -0400
Subject: [PATCH] Emit a warning about channel deprecation.

---
 doc/manual/source/command-ref/nix-channel.md | 6 ++++++
 src/nix-channel/nix-channel.cc               | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/doc/manual/source/command-ref/nix-channel.md b/doc/manual/source/command-ref/nix-channel.md
index 8b58392b7..bc0a90b11 100644
--- a/doc/manual/source/command-ref/nix-channel.md
+++ b/doc/manual/source/command-ref/nix-channel.md
@@ -8,6 +8,12 @@
 
 # Description
 
+> **Warning**
+>
+> nix-channel is deprecated in favor of flakes in Determinate Nix.
+> For a guide on Nix flakes, see: <https://zero-to-nix.com/>.
+> For details and to offer feedback on the deprecation process, see: <https://github.com/DeterminateSystems/nix-src/issues/34>.
+
 Channels are a mechanism for referencing remote Nix expressions and conveniently retrieving their latest version.
 
 The moving parts of channels are:
diff --git a/src/nix-channel/nix-channel.cc b/src/nix-channel/nix-channel.cc
index c0baa4aa2..a6ca6f711 100644
--- a/src/nix-channel/nix-channel.cc
+++ b/src/nix-channel/nix-channel.cc
@@ -164,6 +164,11 @@ static void update(const StringSet & channelNames)
 
 static int main_nix_channel(int argc, char ** argv)
 {
+    warn(
+        "nix-channel is deprecated in favor of flakes in Determinate Nix. \
+For a guide on Nix flakes, see: https://zero-to-nix.com/. \
+For details and to offer feedback on the deprecation process, see: https://github.com/DeterminateSystems/nix-src/issues/34.");
+
     {
         // Figure out the name of the `.nix-channels' file to use
         auto home = getHome();