skip ifds in nix flake show instead of throwing

src/libexpr/eval-error.cc

@@ -110,5 +110,6 @@ template class EvalErrorBuilder<UndefinedVarError>;
 template class EvalErrorBuilder<MissingArgumentError>;
 template class EvalErrorBuilder<InfiniteRecursionError>;
 template class EvalErrorBuilder<InvalidPathError>;
+template class EvalErrorBuilder<IFDError>;
 
 }

src/libexpr/eval-error.hh

@@ -54,6 +54,7 @@ MakeError(TypeError, EvalError);
 MakeError(UndefinedVarError, EvalError);
 MakeError(MissingArgumentError, EvalError);
 MakeError(InfiniteRecursionError, EvalError);
+MakeError(IFDError, EvalBaseError);
 
 struct InvalidPathError : public EvalError
 {

src/libexpr/primops.cc

@@ -91,7 +91,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context, StorePathS
     if (drvs.empty()) return {};
 
     if (isIFD && !settings.enableImportFromDerivation)
-        error<EvalBaseError>(
+        error<IFDError>(
             "cannot build '%1%' during evaluation because the option 'allow-import-from-derivation' is disabled",
             drvs.begin()->to_string(*store)
         ).debugThrow();

src/nix/flake.cc

@@ -1329,18 +1329,34 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                             logger->warn(fmt("%s omitted (use '--all-systems' to show)", concatStringsSep(".", attrPathS)));
                         }
                     } else {
-                        if (visitor.isDerivation())
+                        try {
-                            showDerivation();
+                            if (visitor.isDerivation())
-                        else
+                                showDerivation();
-                            throw Error("expected a derivation");
+                            else
+                                throw Error("expected a derivation");
+                        } 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)));
+                            }
+                        }
                     }
                 }
 
                 else if (attrPath.size() > 0 && attrPathS[0] == "hydraJobs") {
-                    if (visitor.isDerivation())
+                    try {
-                        showDerivation();
+                        if (visitor.isDerivation())
-                    else
+                            showDerivation();
-                        recurse();
+                        else
+                            recurse();
+                    } 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)));
+                        }
+                    }
                 }
 
                 else if (attrPath.size() > 0 && attrPathS[0] == "legacyPackages") {
@@ -1359,11 +1375,19 @@ struct CmdFlakeShow : FlakeCommand, MixJSON
                             logger->warn(fmt("%s omitted (use '--all-systems' to show)", concatStringsSep(".", attrPathS)));
                         }
                     } else {
-                        if (visitor.isDerivation())
+                        try {
-                            showDerivation();
+                            if (visitor.isDerivation())
-                        else if (attrPath.size() <= 2)
+                                showDerivation();
-                            // FIXME: handle recurseIntoAttrs
+                            else if (attrPath.size() <= 2)
-                            recurse();
+                                // FIXME: handle recurseIntoAttrs
+                                recurse();
+                        } 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)));
+                            }
+                        }
                     }
                 }
 

tests/functional/flakes/common.sh

@@ -88,6 +88,19 @@ writeDependentFlake() {
 EOF
 }
 
+writeIfdFlake() {
+    local flakeDir="$1"
+    cat > "$flakeDir/flake.nix" <<EOF
+{
+  outputs = { self }: {
+    packages.$system.default = import ./ifd.nix;
+  };
+}
+EOF
+
+    cp -n ../ifd.nix ../dependencies.nix ../dependencies.builder0.sh "${config_nix}" "$flakeDir/"
+}
+
 writeTrivialFlake() {
     local flakeDir="$1"
     cat > "$flakeDir/flake.nix" <<EOF

tests/functional/flakes/show.sh

@@ -6,7 +6,7 @@ flakeDir=$TEST_ROOT/flake
 mkdir -p "$flakeDir"
 
 writeSimpleFlake "$flakeDir"
-cd "$flakeDir"
+pushd "$flakeDir"
 
 
 # By default: Only show the packages content for the current system and no
@@ -87,3 +87,18 @@ assert show_output.legacyPackages.${builtins.currentSystem}.AAAAAASomeThingsFail
 assert show_output.legacyPackages.${builtins.currentSystem}.simple.name == "simple";
 true
 '
+
+# Test that nix flake show doesn't fail if one of the outputs contains
+# an IFD
+popd
+writeIfdFlake $flakeDir
+pushd $flakeDir
+
+
+nix flake show --json > show-output.json
+nix eval --impure --expr '
+let show_output = builtins.fromJSON (builtins.readFile ./show-output.json);
+in
+assert show_output.packages.${builtins.currentSystem}.default == { };
+true
+'