From dcca8f5be287bf7efd4867d0e0ed7643434a8236 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Mon, 4 Apr 2022 13:11:47 +0200
Subject: [PATCH] tests.pkgs-lib.formats: Detect when impossible input is fed

---
 pkgs/pkgs-lib/tests/formats.nix | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pkgs/pkgs-lib/tests/formats.nix b/pkgs/pkgs-lib/tests/formats.nix
index 1efe9d8686b1..99b88d36ec3c 100644
--- a/pkgs/pkgs-lib/tests/formats.nix
+++ b/pkgs/pkgs-lib/tests/formats.nix
@@ -9,7 +9,11 @@ let
     let
       formatSet = format args;
       config = formatSet.type.merge [] (imap1 (n: def: {
-        value = def;
+        # We check the input values, so that
+        #  - we don't write nonsensical tests that will impede progress
+        #  - the test author has a slightly more realistic view of the
+        #    final format during development.
+        value = lib.throwIfNot (formatSet.type.check def) (builtins.trace def "definition does not pass the type's check function") def;
         file = "def${toString n}";
       }) [ def ]);
     in formatSet.generate "test-format-file" config;