1 files changed, 10 insertions, 5 deletions

diff --git a/src/nix-env/nix-env.cc b/src/nix-env/nix-env.cc
index 10b95dad1..8a7f5f059 100644
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@@ -58,6 +58,7 @@ struct Globals
     bool removeAll;
     string forceName;
     bool prebuiltOnly;
+    bool lazyGeneration;
 };
 
 
@@ -510,7 +511,7 @@ static void installDerivations(Globals & globals,
         if (globals.dryRun) return;
 
         if (createUserEnv(*globals.state, allElems,
-                profile, settings.envKeepDerivations, lockToken)) break;
+                profile, settings.envKeepDerivations, lockToken, globals.lazyGeneration)) break;
     }
 }
 
@@ -524,6 +525,8 @@ static void opInstall(Globals & globals, Strings opFlags, Strings opArgs)
             globals.preserveInstalled = true;
         else if (arg == "--remove-all" || arg == "-r")
             globals.removeAll = true;
+        else if (arg == "--lazy-generation")
+            globals.lazyGeneration = true;
         else throw UsageError(format("unknown flag ‘%1%’") % arg);
     }
 
@@ -617,7 +620,7 @@ static void upgradeDerivations(Globals & globals,
         if (globals.dryRun) return;
 
         if (createUserEnv(*globals.state, newElems,
-                globals.profile, settings.envKeepDerivations, lockToken)) break;
+                globals.profile, settings.envKeepDerivations, lockToken, globals.lazyGeneration)) break;
     }
 }
 
@@ -681,7 +684,7 @@ static void opSetFlag(Globals & globals, Strings opFlags, Strings opArgs)
 
         /* Write the new user environment. */
         if (createUserEnv(*globals.state, installedElems,
-                globals.profile, settings.envKeepDerivations, lockToken)) break;
+                globals.profile, settings.envKeepDerivations, lockToken, globals.lazyGeneration)) break;
     }
 }
 
@@ -718,7 +721,8 @@ static void opSet(Globals & globals, Strings opFlags, Strings opArgs)
     }
 
     debug(format("switching to new user environment"));
-    Path generation = createGeneration(globals.profile, drv.queryOutPath());
+    Path generation = createGeneration(globals.profile, drv.queryOutPath(),
+                                       globals.lazyGeneration);
     switchLink(globals.profile, generation);
 }
 
@@ -751,7 +755,7 @@ static void uninstallDerivations(Globals & globals, Strings & selectors,
         if (globals.dryRun) return;
 
         if (createUserEnv(*globals.state, newElems,
-                profile, settings.envKeepDerivations, lockToken)) break;
+                profile, settings.envKeepDerivations, lockToken, globals.lazyGeneration)) break;
     }
 }
 
@@ -1355,6 +1359,7 @@ int main(int argc, char * * argv)
         globals.preserveInstalled = false;
         globals.removeAll = false;
         globals.prebuiltOnly = false;
+        globals.lazyGeneration = false;
 
         parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
             Operation oldOp = op;