From bb601784834fa6498d0e0676c53c37a59b506cbc Mon Sep 17 00:00:00 2001
From: Max <max@privatevoid.net>
Date: Thu, 1 Sep 2022 22:02:38 +0200
Subject: [PATCH] nix flake show: don't evaluate derivations for foreign
 systems by default

---
 src/nix/flake.cc | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index c28211c46..ad70681ee 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -955,6 +955,7 @@ struct CmdFlakeArchive : FlakeCommand, MixJSON, MixDryRun
 struct CmdFlakeShow : FlakeCommand, MixJSON
 {
     bool showLegacy = false;
+    bool showForeign = false;
 
     CmdFlakeShow()
     {
@@ -963,6 +964,11 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
             .description = "Show the contents of the `legacyPackages` output.",
             .handler = {&showLegacy, true}
         });
+        addFlag({
+            .longName = "foreign",
+            .description = "Show the contents of outputs for foreign systems.",
+            .handler = {&showForeign, true}
+        });
     }
 
     std::string description() override
@@ -983,6 +989,7 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
 
         auto state = getEvalState();
         auto flake = std::make_shared<LockedFlake>(lockFlake());
+        auto localSystem = std::string(settings.thisSystem.get());
 
         std::function<nlohmann::json(
             eval_cache::AttrCursor & visitor,
@@ -1073,10 +1080,18 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                     || (attrPath.size() == 3 && (attrPathS[0] == "checks" || attrPathS[0] == "packages" || attrPathS[0] == "devShells"))
                     )
                 {
-                    if (visitor.isDerivation())
-                        showDerivation();
-                    else
-                        throw Error("expected a derivation");
+                    if (!showForeign && std::string(attrPathS[1]) != localSystem) {
+                        if (!json)
+                            logger->cout(fmt("%s " ANSI_WARNING "omitted" ANSI_NORMAL " (use '--foreign' to show)", headerPrefix));
+                        else {
+                            logger->warn(fmt("%s omitted (use '--foreign' to show)", concatStringsSep(".", attrPathS)));
+                        }
+                    } else {
+                        if (visitor.isDerivation())
+                            showDerivation();
+                        else
+                            throw Error("expected a derivation");
+                    }
                 }
 
                 else if (attrPath.size() > 0 && attrPathS[0] == "hydraJobs") {