From 613a98461fabecf819afef74155c9934c98456b2 Mon Sep 17 00:00:00 2001
From: Adam Dinwoodie <adam@dinwoodie.org>
Date: Sat, 9 Aug 2025 18:31:14 +0100
Subject: [PATCH] fetchtorrent: check JSON config usage correctly

The arguments to `fetchtorrent` are supposed to throw an error if the
user attempts to specify JSON configuration when they're not using the
transmission backend, however a logic error means the error will never
be thrown.

Move the test to somewhere where the behaviour will actually be checked.
---
 pkgs/build-support/fetchtorrent/default.nix | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/pkgs/build-support/fetchtorrent/default.nix b/pkgs/build-support/fetchtorrent/default.nix
index d281e71fe4ae..48c781d864f8 100644
--- a/pkgs/build-support/fetchtorrent/default.nix
+++ b/pkgs/build-support/fetchtorrent/default.nix
@@ -18,11 +18,7 @@ in
       "bittorrent"
     else
       "bittorrent-" + builtins.head (builtins.match urlRegexp url),
-  config ?
-    if (backend == "transmission") then
-      { }
-    else
-      throw "json config for configuring fetchFromBitorrent only works with the transmission backend",
+  config ? { },
   hash,
   backend ? "transmission",
   recursiveHash ? true,
@@ -44,6 +40,9 @@ let
   '';
   jsonConfig = (formats.json { }).generate "jsonConfig" config;
 in
+assert lib.assertMsg (config != { } -> backend == "transmission") ''
+  json config for configuring fetchtorrent only works with the transmission backend
+'';
 runCommand name
   {
     inherit meta;