From 60d48eda2354dfa6d23ed3feb7b23ac25b34edcf Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 31 Jan 2023 18:16:31 +0100
Subject: nix flake show: Ignore empty attrsets

For frameworks it's important that structures are as lazy as possible
to prevent infinite recursions, performance issues and errors that
aren't related to the thing to evaluate. As a consequence, they have
to emit more attributes than strictly (sic) necessary.
However, these attributes with empty values are not useful to the user
so we omit them.
---
 tests/flakes/show.sh | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'tests/flakes')

diff --git a/tests/flakes/show.sh b/tests/flakes/show.sh
index 995de8dc3..dd13264b9 100644
--- a/tests/flakes/show.sh
+++ b/tests/flakes/show.sh
@@ -37,3 +37,30 @@ in
 assert show_output.legacyPackages.${builtins.currentSystem}.hello.name == "simple";
 true
 '
+
+# Test that attributes are only reported when they have actual content
+cat >flake.nix <<EOF
+{
+  description = "Bla bla";
+
+  outputs = inputs: rec {
+    apps.$system = { };
+    checks.$system = { };
+    devShells.$system = { };
+    legacyPackages.$system = { };
+    packages.$system = { };
+    packages.someOtherSystem = { };
+
+    formatter = { };
+    nixosConfigurations = { };
+    nixosModules = { };
+  };
+}
+EOF
+nix flake show --json --all-systems > show-output.json
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output == { };
+true
+'
-- 
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