From 68987761ef2028f6733aab943e2a3cdc0632cbb4 Mon Sep 17 00:00:00 2001
From: Uluc Sengil <uluc.sengil@helsing.ai>
Date: Tue, 10 Jun 2025 14:14:43 +0200
Subject: [PATCH 1/2] add layers to catching IFDs in `nix flake show`

---
 src/nix/flake.cc | 40 +++++++++++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 9 deletions(-)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index a7b72c7e1..3bbfe9b22 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -1153,10 +1153,15 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                 if ((attrPathS[0] == "apps" || attrPathS[0] == "checks" || attrPathS[0] == "devShells"
                      || attrPathS[0] == "legacyPackages" || attrPathS[0] == "packages")
                     && (attrPathS.size() == 1 || attrPathS.size() == 2)) {
-                    for (const auto & subAttr : visitor2->getAttrs()) {
-                        if (hasContent(*visitor2, attrPath2, subAttr)) {
-                            return true;
+                    try {
+                        for (const auto & subAttr : visitor2->getAttrs()) {
+                            if (hasContent(*visitor2, attrPath2, subAttr)) {
+                                return true;
+                            }
                         }
+                    } catch (IFDError & e) {
+                        // allow IFD errors here; as we handle them during `visit()`
+                        return true;
                     }
                     return false;
                 }
@@ -1164,10 +1169,14 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                 if ((attrPathS.size() == 1)
                     && (attrPathS[0] == "formatter" || attrPathS[0] == "nixosConfigurations"
                         || attrPathS[0] == "nixosModules" || attrPathS[0] == "overlays")) {
-                    for (const auto & subAttr : visitor2->getAttrs()) {
-                        if (hasContent(*visitor2, attrPath2, subAttr)) {
-                            return true;
+                    try {
+                        for (const auto & subAttr : visitor2->getAttrs()) {
+                            if (hasContent(*visitor2, attrPath2, subAttr)) {
+                                return true;
+                            }
                         }
+                    } catch (IFDError & e) {
+                        return true;
                     }
                     return false;
                 }
@@ -1204,9 +1213,22 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                     if (!json)
                         logger->cout("%s", headerPrefix);
                     std::vector<Symbol> attrs;
-                    for (const auto & attr : visitor.getAttrs()) {
-                        if (hasContent(visitor, attrPath, attr))
-                            attrs.push_back(attr);
+                    try {
+                        for (const auto & attr : visitor.getAttrs()) {
+                            if (hasContent(visitor, attrPath, attr))
+                                attrs.push_back(attr);
+                        }
+                        if (!json)
+                            logger->cout("%s", headerPrefix);
+                    } catch (IFDError & e) {
+                        if (!json) {
+                            logger->cout(
+                                fmt("%s " ANSI_WARNING "omitted due to use of import from derivation" ANSI_NORMAL,
+                                    headerPrefix));
+                        } else {
+                            logger->warn(fmt(
+                                "%s omitted due to use of import from derivation", concatStringsSep(".", attrPathS)));
+                        }
                     }
 
                     for (const auto & [i, attr] : enumerate(attrs)) {

From 5c329233977e24e913f084979bead5befe90dc3a Mon Sep 17 00:00:00 2001
From: Uluc Sengil <uluc.sengil@helsing.ai>
Date: Wed, 25 Jun 2025 10:41:56 +0200
Subject: [PATCH 2/2] add regression tests

---
 tests/functional/flakes/common.sh | 2 ++
 tests/functional/flakes/show.sh   | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/tests/functional/flakes/common.sh b/tests/functional/flakes/common.sh
index 422cab96c..2950b3898 100644
--- a/tests/functional/flakes/common.sh
+++ b/tests/functional/flakes/common.sh
@@ -94,6 +94,8 @@ writeIfdFlake() {
 {
   outputs = { self }: {
     packages.$system.default = import ./ifd.nix;
+    checks.$system = import ./ifd.nix;
+    formatter = import ./ifd.nix;
   };
 }
 EOF
diff --git a/tests/functional/flakes/show.sh b/tests/functional/flakes/show.sh
index 7fcc6aca9..5407e0086 100755
--- a/tests/functional/flakes/show.sh
+++ b/tests/functional/flakes/show.sh
@@ -100,5 +100,7 @@ nix eval --impure --expr '
 let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
 in
 assert show_output.packages.${builtins.currentSystem}.default == { };
+assert show_output.checks.${builtins.currentSystem} == { };
+assert show_output.formatter == { };
 true
 '