Throw an error if --arg / --argstr is used with a flake

Fixes #3949.

src/libcmd/installables.cc

@@ -496,6 +496,23 @@ static std::string showAttrPaths(const std::vector<std::string> & paths)
     return s;
 }
 
+InstallableFlake::InstallableFlake(
+    SourceExprCommand * cmd,
+    ref<EvalState> state,
+    FlakeRef && flakeRef,
+    Strings && attrPaths,
+    Strings && prefixes,
+    const flake::LockFlags & lockFlags)
+    : InstallableValue(state),
+      flakeRef(flakeRef),
+      attrPaths(attrPaths),
+      prefixes(prefixes),
+      lockFlags(lockFlags)
+{
+    if (cmd && cmd->getAutoArgs(*state)->size())
+        throw UsageError("'--arg' and '--argstr' are incompatible with flakes");
+}
+
 std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableFlake::toDerivation()
 {
     auto lockedFlake = getLockedFlake();
@@ -628,9 +645,12 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
             try {
                 auto [flakeRef, fragment] = parseFlakeRefWithFragment(s, absPath("."));
                 result.push_back(std::make_shared<InstallableFlake>(
-                        getEvalState(), std::move(flakeRef),
+                        this,
+                        getEvalState(),
+                        std::move(flakeRef),
                         fragment == "" ? getDefaultFlakeAttrPaths() : Strings{fragment},
-                        getDefaultFlakeAttrPathPrefixes(), lockFlags));
+                        getDefaultFlakeAttrPathPrefixes(),
+                        lockFlags));
                 continue;
             } catch (...) {
                 ex = std::current_exception();

src/libcmd/installables.hh

@@ -104,11 +104,13 @@ struct InstallableFlake : InstallableValue
     const flake::LockFlags & lockFlags;
     mutable std::shared_ptr<flake::LockedFlake> _lockedFlake;
 
-    InstallableFlake(ref<EvalState> state, FlakeRef && flakeRef,
-        Strings && attrPaths, Strings && prefixes, const flake::LockFlags & lockFlags)
-        : InstallableValue(state), flakeRef(flakeRef), attrPaths(attrPaths),
-          prefixes(prefixes), lockFlags(lockFlags)
-    { }
+    InstallableFlake(
+        SourceExprCommand * cmd,
+        ref<EvalState> state,
+        FlakeRef && flakeRef,
+        Strings && attrPaths,
+        Strings && prefixes,
+        const flake::LockFlags & lockFlags);
 
     std::string what() override { return flakeRef.to_string() + "#" + *attrPaths.begin(); }
 

src/nix/bundle.cc

@@ -74,7 +74,7 @@ struct CmdBundle : InstallableCommand
 
         auto [bundlerFlakeRef, bundlerName] = parseFlakeRefWithFragment(bundler, absPath("."));
         const flake::LockFlags lockFlags{ .writeLockFile = false };
-        auto bundler = InstallableFlake(
+        auto bundler = InstallableFlake(this,
             evalState, std::move(bundlerFlakeRef),
             Strings{bundlerName == "" ? "defaultBundler" : bundlerName},
             Strings({"bundlers."}), lockFlags);

src/nix/develop.cc

@@ -443,6 +443,7 @@ struct CmdDevelop : Common, MixEnvironment
             auto state = getEvalState();
 
             auto bashInstallable = std::make_shared<InstallableFlake>(
+                this,
                 state,
                 installable->nixpkgsFlakeRef(),
                 Strings{"bashInteractive"},

src/nix/flake.cc

@@ -595,7 +595,7 @@ struct CmdFlakeInitCommon : virtual Args, EvalCommand
 
         auto [templateFlakeRef, templateName] = parseFlakeRefWithFragment(templateUrl, absPath("."));
 
-        auto installable = InstallableFlake(
+        auto installable = InstallableFlake(nullptr,
             evalState, std::move(templateFlakeRef),
             Strings{templateName == "" ? "defaultTemplate" : templateName},
             Strings(attrsPathPrefixes), lockFlags);

src/nix/profile.cc

@@ -399,7 +399,13 @@ struct CmdProfileUpgrade : virtual SourceExprCommand, MixDefaultProfile, MixProf
                 Activity act(*logger, lvlChatty, actUnknown,
                     fmt("checking '%s' for updates", element.source->attrPath));
 
-                InstallableFlake installable(getEvalState(), FlakeRef(element.source->originalRef), {element.source->attrPath}, {}, lockFlags);
+                InstallableFlake installable(
+                    this,
+                    getEvalState(),
+                    FlakeRef(element.source->originalRef),
+                    {element.source->attrPath},
+                    {},
+                    lockFlags);
 
                 auto [attrPath, resolvedRef, drv] = installable.toDerivation();