Add testcase for nix develop with __structuredAttrs

tests/shell.nix

@@ -8,6 +8,14 @@ let pkgs = rec {
     for pkg in $buildInputs; do
       export PATH=$PATH:$pkg/bin
     done
+
+    # mimic behavior of stdenv for `$out` etc. for structured attrs.
+    if [ -n "''${ATTRS_SH_FILE}" ]; then
+      for o in "''${!outputs[@]}"; do
+        eval "''${o}=''${outputs[$o]}"
+        export "''${o}"
+      done
+    fi
   '';
 
   stdenv = mkDerivation {

tests/structured-attrs-shell.nix

@@ -6,10 +6,12 @@ let
       mkdir $out; echo bla > $out/bla
     '';
   };
+  inherit (import ./shell.nix { inNixShell = true; }) stdenv;
 in
 mkDerivation {
   name = "structured2";
   __structuredAttrs = true;
+  inherit stdenv;
   outputs = [ "out" "dev" ];
   my.list = [ "a" "b" "c" ];
   exportReferencesGraph.refs = [ dep ];

tests/structured-attrs.sh

@@ -12,3 +12,8 @@ nix-build structured-attrs.nix -A all -o $TEST_ROOT/result
 export NIX_BUILD_SHELL=$SHELL
 env NIX_PATH=nixpkgs=shell.nix nix-shell structured-attrs-shell.nix \
     --run 'test -e .attrs.json; test "3" = "$(jq ".my.list|length" < $ATTRS_JSON_FILE)"'
+
+# `nix develop` is a slightly special way of dealing with environment vars, it parses
+# these from a shell-file exported from a derivation. This is to test especially `outputs`
+# (which is an associative array in thsi case) being fine.
+nix develop -f structured-attrs-shell.nix -c bash -c 'test -n "$out"'