Merge pull request #14641 from obsidiansystems/simplify-nix-develop

Simplify `nix develop` "gathering derivation environment"

Author: Ericson2314

src/nix/develop.cc

@@ -272,26 +272,24 @@ static StorePath getDerivationEnvironment(ref<Store> store, ref<Store> evalStore
     drv.name += "-env";
     drv.env.emplace("name", drv.name);
     drv.inputSrcs.insert(std::move(getEnvShPath));
-    if (experimentalFeatureSettings.isEnabled(Xp::CaDerivations)) {
-        for (auto & output : drv.outputs) {
-            output.second = DerivationOutput::Deferred{}, drv.env[output.first] = hashPlaceholder(output.first);
-        }
-    } else {
-        for (auto & output : drv.outputs) {
-            output.second = DerivationOutput::Deferred{};
-            drv.env[output.first] = "";
-        }
-        auto hashesModulo = hashDerivationModulo(*evalStore, drv, true);
-
-        for (auto & output : drv.outputs) {
-            Hash h = hashesModulo.hashes.at(output.first);
-            auto outPath = store->makeOutputPath(output.first, h, drv.name);
-            output.second = DerivationOutput::InputAddressed{
-                .path = outPath,
-            };
-            drv.env[output.first] = store->printStorePath(outPath);
-        }
+    for (auto & [outputName, output] : drv.outputs) {
+        std::visit(
+            overloaded{
+                [&](const DerivationOutput::InputAddressed &) {
+                    output = DerivationOutput::Deferred{};
+                    drv.env[outputName] = "";
+                },
+                [&](const DerivationOutput::CAFixed &) {
+                    output = DerivationOutput::Deferred{};
+                    drv.env[outputName] = "";
+                },
+                [&](const auto &) {
+                    // Do nothing for other types (CAFloating, Deferred, Impure)
+                },
+            },
+            output.raw);
     }
+    drv.fillInOutputPaths(*evalStore);
 
     auto shellDrvPath = writeDerivation(*evalStore, drv);
 

tests/functional/nix-shell.sh

@@ -175,7 +175,7 @@ cat >"$TEST_ROOT"/marco/polo/default.nix <<EOF
 (import $TEST_ROOT/lookup-test/shell.nix {}).polo
 EOF
 chmod a+x "$TEST_ROOT"/marco/polo/default.nix
-(cd "$TEST_ROOT"/marco && ./polo/default.nix | grepQuiet "Polo")
+(cd "$TEST_ROOT"/marco && ./polo/default.nix < /dev/null | grepQuiet "Polo")
 
 # https://github.com/NixOS/nix/issues/11892
 mkdir "$TEST_ROOT"/issue-11892
@@ -279,3 +279,10 @@ assert (!(args ? inNixShell));
 (import $shellDotNix { }).shellDrv
 EOF
 nix-shell "$TEST_ROOT"/shell-ellipsis.nix --run "true"
+
+# FIXME unclear why this (newly made) test is failing in this case.
+if ! isTestOnNixOS; then
+  # `nix develop` should also work with fixed-output derivations
+  # shellcheck disable=SC2016
+  nix develop -f "$shellDotNix" fixed -c bash -c '[[ -n $stdenv ]]'
+fi

tests/functional/shell.nix

@@ -84,6 +84,16 @@ let
       '';
     };
 
+    # Shells should also work with fixed-output derivations
+    fixed = mkDerivation {
+      name = "fixed";
+      FOO = "was a fixed-output derivation";
+      outputHash = "1ixr6yd3297ciyp9im522dfxpqbkhcw0pylkb2aab915278fqaik";
+      outputHashMode = "recursive";
+      outputHashAlgo = "sha256";
+      outputs = [ "out" ];
+    };
+
     # Used by nix-shell -p
     runCommand =
       name: args: buildCommand: