From f68a3023cd4879b774631adcf3a52cdb313a5e73 Mon Sep 17 00:00:00 2001
From: Lorenz Leutgeb <lorenz@leutgeb.xyz>
Date: Wed, 25 Oct 2023 00:45:29 +0200
Subject: [PATCH] fix: Make `nix flake show --json` print flake ref

Fixes https://github.com/NixOS/nix/issues/9230

Breaking change.
---
 src/nix/flake.cc                |  3 ++-
 tests/functional/flakes/show.sh | 25 ++++++++++++++++++++-----
 2 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 0116eff2e..a1836bd07 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -1315,7 +1315,8 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
 
         auto cache = openEvalCache(*state, flake);
 
-        auto j = visit(*cache->getRoot(), {}, fmt(ANSI_BOLD "%s" ANSI_NORMAL, flake->flake.lockedRef), "");
+        auto lockedRef = flake->flake.lockedRef.to_string();
+        auto j = nlohmann::json::object({ {lockedRef, visit(*cache->getRoot(), {}, fmt(ANSI_BOLD "%s" ANSI_NORMAL, lockedRef), "")} });
         if (json)
             logger->cout("%s", j.dump());
     }
diff --git a/tests/functional/flakes/show.sh b/tests/functional/flakes/show.sh
index a3d300552..48b5b12bc 100644
--- a/tests/functional/flakes/show.sh
+++ b/tests/functional/flakes/show.sh
@@ -6,10 +6,25 @@ mkdir -p "$flakeDir"
 writeSimpleFlake "$flakeDir"
 cd "$flakeDir"
 
+# Check the flake reference that was produced.
+nix flake show --json > output.json
+nix eval --impure --expr '
+with builtins;
+let
+  flakeRef = parseFlakeRef (head (attrNames (fromJSON (readFile ./output.json))));
+  narHash = if match ".*darwin" currentSystem != null
+    then "sha256-MhmXWT9U41eDFezA02mAj3PxBO21icT5VvvPSC1epDU="
+    else "sha256-op9gWTEmDXergxx2PojSTrxVREG7NLcrhySSun3DQd0="
+  ;
+in
+assert flakeRef.narHash == narHash;
+assert flakeRef.type == "path";
+true
+'
 
 # By default: Only show the packages content for the current system and no
 # legacyPackages at all
-nix flake show --json > show-output.json
+nix flake show --json | jq 'to_entries[0].value' > show-output.json
 nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in
@@ -20,7 +35,7 @@ true
 '
 
 # With `--all-systems`, show the packages for all systems
-nix flake show --json --all-systems > show-output.json
+nix flake show --json --all-systems | jq 'to_entries[0].value' > show-output.json
 nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in
@@ -30,7 +45,7 @@ true
 '
 
 # With `--legacy`, show the legacy packages
-nix flake show --json --legacy > show-output.json
+nix flake show --json --legacy | jq 'to_entries[0].value' > show-output.json
 nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in
@@ -57,7 +72,7 @@ cat >flake.nix <<EOF
   };
 }
 EOF
-nix flake show --json --all-systems > show-output.json
+nix flake show --json --all-systems | jq 'to_entries[0].value' > show-output.json
 nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in
@@ -77,7 +92,7 @@ cat >flake.nix <<EOF
   };
 }
 EOF
-nix flake show --json --legacy --all-systems > show-output.json
+nix flake show --json --legacy --all-systems | jq 'to_entries[0].value' > show-output.json
 nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in