3 files changed, 109 insertions, 23 deletions

diff --git a/src/nix/command.hh b/src/nix/command.hh
index 26c308331..659b724c3 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -38,6 +38,13 @@ struct Buildable
 
 typedef std::vector<Buildable> Buildables;
 
+struct App
+{
+    PathSet context;
+    Path program;
+    // FIXME: add args, sandbox settings, metadata, ...
+};
+
 struct Installable
 {
     virtual std::string what() = 0;
@@ -49,6 +56,8 @@ struct Installable
 
     Buildable toBuildable();
 
+    App toApp(EvalState & state);
+
     virtual Value * toValue(EvalState & state)
     {
         throw Error("argument '%s' cannot be evaluated", what());
diff --git a/src/nix/installables.cc b/src/nix/installables.cc
index eb3c27d6b..b6f05b314 100644
--- a/src/nix/installables.cc
+++ b/src/nix/installables.cc
@@ -68,6 +68,28 @@ Buildable Installable::toBuildable()
     return std::move(buildables[0]);
 }
 
+App Installable::toApp(EvalState & state)
+{
+    auto v = toValue(state);
+
+    state.forceAttrs(*v);
+
+    auto aType = v->attrs->need(state.sType);
+    if (state.forceStringNoCtx(*aType.value, *aType.pos) != "app")
+        throw Error("value does not have type 'app', at %s", *aType.pos);
+
+    App app;
+
+    auto aProgram = v->attrs->need(state.symbols.create("program"));
+    app.program = state.forceString(*aProgram.value, app.context, *aProgram.pos);
+
+    // FIXME: check that 'program' is in the closure of 'context'.
+    if (!state.store->isInStore(app.program))
+        throw Error("app program '%s' is not in the Nix store", app.program);
+
+    return app;
+}
+
 struct InstallableStorePath : Installable
 {
     Path storePath;
diff --git a/src/nix/run.cc b/src/nix/run.cc
index 35b763345..00a682832 100644
--- a/src/nix/run.cc
+++ b/src/nix/run.cc
@@ -8,6 +8,7 @@
 #include "fs-accessor.hh"
 #include "progress-bar.hh"
 #include "affinity.hh"
+#include "eval.hh"
 
 #if __linux__
 #include <sys/mount.h>
@@ -19,7 +20,44 @@ using namespace nix;
 
 std::string chrootHelperName = "__run_in_chroot";
 
-struct CmdRun : InstallablesCommand
+struct RunCommon : virtual Command
+{
+    void runProgram(ref<Store> store,
+        const std::string & program,
+        const Strings & args)
+    {
+        stopProgressBar();
+
+        restoreSignals();
+
+        restoreAffinity();
+
+        /* If this is a diverted store (i.e. its "logical" location
+           (typically /nix/store) differs from its "physical" location
+           (e.g. /home/eelco/nix/store), then run the command in a
+           chroot. For non-root users, this requires running it in new
+           mount and user namespaces. Unfortunately,
+           unshare(CLONE_NEWUSER) doesn't work in a multithreaded
+           program (which "nix" is), so we exec() a single-threaded
+           helper program (chrootHelper() below) to do the work. */
+        auto store2 = store.dynamic_pointer_cast<LocalStore>();
+
+        if (store2 && store->storeDir != store2->realStoreDir) {
+            Strings helperArgs = { chrootHelperName, store->storeDir, store2->realStoreDir, program };
+            for (auto & arg : args) helperArgs.push_back(arg);
+
+            execv(readLink("/proc/self/exe").c_str(), stringsToCharPtrs(helperArgs).data());
+
+            throw SysError("could not execute chroot helper");
+        }
+
+        execvp(program.c_str(), stringsToCharPtrs(args).data());
+
+        throw SysError("unable to execute '%s'", program);
+    }
+};
+
+struct CmdRun : InstallablesCommand, RunCommon
 {
     std::vector<std::string> command = { "bash" };
     StringSet keep, unset;
@@ -147,42 +185,59 @@ struct CmdRun : InstallablesCommand
 
         setenv("PATH", concatStringsSep(":", unixPath).c_str(), 1);
 
-        std::string cmd = *command.begin();
         Strings args;
         for (auto & arg : command) args.push_back(arg);
 
-        stopProgressBar();
+        runProgram(store, *command.begin(), args);
+    }
+};
 
-        restoreSignals();
+static RegisterCommand r1(make_ref<CmdRun>());
 
-        restoreAffinity();
+struct CmdApp : InstallableCommand, RunCommon
+{
+    CmdApp()
+    {
+    }
 
-        /* If this is a diverted store (i.e. its "logical" location
-           (typically /nix/store) differs from its "physical" location
-           (e.g. /home/eelco/nix/store), then run the command in a
-           chroot. For non-root users, this requires running it in new
-           mount and user namespaces. Unfortunately,
-           unshare(CLONE_NEWUSER) doesn't work in a multithreaded
-           program (which "nix" is), so we exec() a single-threaded
-           helper program (chrootHelper() below) to do the work. */
-        auto store2 = store.dynamic_pointer_cast<LocalStore>();
+    std::string name() override
+    {
+        return "app";
+    }
 
-        if (store2 && store->storeDir != store2->realStoreDir) {
-            Strings helperArgs = { chrootHelperName, store->storeDir, store2->realStoreDir, cmd };
-            for (auto & arg : args) helperArgs.push_back(arg);
+    std::string description() override
+    {
+        return "run a Nix application";
+    }
 
-            execv(readLink("/proc/self/exe").c_str(), stringsToCharPtrs(helperArgs).data());
+    Examples examples() override
+    {
+        return {
+            Example{
+                "To run Blender:",
+                "nix app blender-bin"
+            },
+        };
+    }
 
-            throw SysError("could not execute chroot helper");
-        }
+    Strings getDefaultFlakeAttrPaths() override
+    {
+        return {"defaultApp"};
+    }
 
-        execvp(cmd.c_str(), stringsToCharPtrs(args).data());
+    void run(ref<Store> store) override
+    {
+        auto state = getEvalState();
+
+        auto app = installable->toApp(*state);
 
-        throw SysError("unable to exec '%s'", cmd);
+        state->realiseContext(app.context);
+
+        runProgram(store, app.program, {app.program});
     }
 };
 
-static RegisterCommand r1(make_ref<CmdRun>());
+static RegisterCommand r2(make_ref<CmdApp>());
 
 void chrootHelper(int argc, char * * argv)
 {