diff --git a/src/nix/flake.cc b/src/nix/flake.cc index d2f68c37c..c025bc7a6 100644 --- a/src/nix/flake.cc +++ b/src/nix/flake.cc @@ -1002,6 +1002,61 @@ struct CmdFlakeShow : FlakeCommand, MixJSON auto flake = std::make_shared(lockFlake()); auto localSystem = std::string(settings.thisSystem.get()); + std::function &attrPath, + const Symbol &attr)> hasContent; + + // For frameworks it's important that structures are as lazy as possible + // to prevent infinite recursions, performance issues and errors that + // aren't related to the thing to evaluate. As a consequence, they have + // to emit more attributes than strictly (sic) necessary. + // However, these attributes with empty values are not useful to the user + // so we omit them. + hasContent = [&]( + eval_cache::AttrCursor & visitor, + const std::vector &attrPath, + const Symbol &attr) -> bool + { + auto attrPath2(attrPath); + attrPath2.push_back(attr); + auto attrPathS = state->symbols.resolve(attrPath2); + const auto & attrName = state->symbols[attr]; + + auto visitor2 = visitor.getAttr(attrName); + + 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; + } + } + return false; + } + + 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; + } + } + return false; + } + + // If we don't recognize it, it's probably content + return true; + }; + std::function & attrPath, @@ -1027,7 +1082,12 @@ struct CmdFlakeShow : FlakeCommand, MixJSON { if (!json) logger->cout("%s", headerPrefix); - auto attrs = visitor.getAttrs(); + std::vector attrs; + for (const auto &attr : visitor.getAttrs()) { + if (hasContent(visitor, attrPath, attr)) + attrs.push_back(attr); + } + for (const auto & [i, attr] : enumerate(attrs)) { const auto & attrName = state->symbols[attr]; bool last = i + 1 == attrs.size(); diff --git a/tests/flakes/show.sh b/tests/flakes/show.sh index 995de8dc3..dd13264b9 100644 --- a/tests/flakes/show.sh +++ b/tests/flakes/show.sh @@ -37,3 +37,30 @@ in assert show_output.legacyPackages.${builtins.currentSystem}.hello.name == "simple"; true ' + +# Test that attributes are only reported when they have actual content +cat >flake.nix < show-output.json +nix eval --impure --expr ' +let show_output = builtins.fromJSON (builtins.readFile ./show-output.json); +in +assert show_output == { }; +true +'