libcmd: make Repl instances proper scopes

there's no reason to ever *own* a repl instance. everything either wants
to run a repl and receive the result of that run, or run a repl and then
totally ignore the result. allowing non-transient repl instances doesn't
do anything useful for us, unless making ownership analysis hard counts.

this also fixes a bug in which a repl could ignore the store it was told
to use during construction, using the one returned by openStore instead.
this never showed up in lix because openStore() was always passed anyway

Change-Id: If2b1ad24ab74377340199b36af1dd629d7ce3f25

lix/libcmd/repl.cc

@@ -1092,43 +1092,30 @@ Value * NixRepl::evalFile(SourcePath & path)
     return result;
 }
 
-
-std::unique_ptr<AbstractNixRepl> AbstractNixRepl::create(
-   const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,
-   std::function<AnnotatedValues()> getValues)
+ReplExitStatus AbstractNixRepl::run(
+    const SearchPath & searchPath,
+    nix::ref<Store> store,
+    ref<EvalState> state,
+    std::function<AnnotatedValues()> getValues,
+    const ValMap & extraEnv,
+    Bindings * autoArgs
+)
 {
-    return std::make_unique<NixRepl>(
-        searchPath,
-        openStore(),
-        state,
-        getValues
+    NixRepl repl(searchPath, store, state, getValues);
+
+    repl.autoArgs = autoArgs;
+    repl.initEnv();
+    for (auto & [name, value] : extraEnv) {
+        repl.addVarToScope(repl.state->symbols.create(name), *value);
+    }
+    return repl.mainLoop();
+}
+
+ReplExitStatus AbstractNixRepl::runSimple(ref<EvalState> evalState, const ValMap & extraEnv)
+{
+    return run(
+        {}, openStore(), evalState, [] {  return AnnotatedValues{}; }, extraEnv, nullptr
     );
 }
 
-
-ReplExitStatus AbstractNixRepl::runSimple(
-    ref<EvalState> evalState,
-    const ValMap & extraEnv)
-{
-    auto getValues = [&]()->NixRepl::AnnotatedValues{
-        NixRepl::AnnotatedValues values;
-        return values;
-    };
-    SearchPath searchPath = {};
-    auto repl = std::make_unique<NixRepl>(
-            searchPath,
-            openStore(),
-            evalState,
-            getValues
-        );
-
-    repl->initEnv();
-
-    // add 'extra' vars.
-    for (auto & [name, value] : extraEnv)
-        repl->addVarToScope(repl->state->symbols.create(name), *value);
-
-    return repl->mainLoop();
-}
-
 }

lix/libcmd/repl.hh

@@ -7,6 +7,21 @@ namespace nix {
 
 struct AbstractNixRepl
 {
+    typedef std::vector<std::pair<Value*,std::string>> AnnotatedValues;
+
+    static ReplExitStatus
+    run(const SearchPath & searchPath,
+        nix::ref<Store> store,
+        ref<EvalState> state,
+        std::function<AnnotatedValues()> getValues,
+        const ValMap & extraEnv,
+        Bindings * autoArgs);
+
+    static ReplExitStatus runSimple(
+        ref<EvalState> evalState,
+        const ValMap & extraEnv);
+
+protected:
     ref<EvalState> state;
     Bindings * autoArgs;
 
@@ -14,19 +29,6 @@ struct AbstractNixRepl
         : state(state)
     { }
 
-    virtual ~AbstractNixRepl()
-    { }
-
-    typedef std::vector<std::pair<Value*,std::string>> AnnotatedValues;
-
-    static std::unique_ptr<AbstractNixRepl> create(
-        const SearchPath & searchPath, nix::ref<Store> store, ref<EvalState> state,
-        std::function<AnnotatedValues()> getValues);
-
-    static ReplExitStatus runSimple(
-        ref<EvalState> evalState,
-        const ValMap & extraEnv);
-
     virtual void initEnv() = 0;
 
     virtual ReplExitStatus mainLoop() = 0;

lix/nix/repl.cc

@@ -86,15 +86,7 @@ struct CmdRepl : RawInstallablesCommand
             }
             return values;
         };
-        auto repl = AbstractNixRepl::create(
-            searchPath,
-            openStore(),
-            state,
-            getValues
-        );
-        repl->autoArgs = getAutoArgs(*repl->state);
-        repl->initEnv();
-        repl->mainLoop();
+        AbstractNixRepl::run(searchPath, openStore(), state, getValues, {}, getAutoArgs(*state));
     }
 };