From 8fb17e8f3febf3cfa56f5ce34f8d28cc0b2b4618 Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Mon, 8 Apr 2024 23:08:46 +0800
Subject: [PATCH] libnixt: allow eval decoded expression (#388)

---
 libnixt/meson.build                           |  7 +++-
 libnixt/tools/meson.build                     |  1 -
 .../{nixt-decode/Main.cpp => nixt-decode.cpp} | 32 +++++++++++++++++--
 libnixt/tools/nixt-decode/meson.build         |  5 ---
 4 files changed, 36 insertions(+), 9 deletions(-)
 delete mode 100644 libnixt/tools/meson.build
 rename libnixt/tools/{nixt-decode/Main.cpp => nixt-decode.cpp} (50%)
 delete mode 100644 libnixt/tools/nixt-decode/meson.build

diff --git a/libnixt/meson.build b/libnixt/meson.build
index 78f02d79c..6b3460257 100644
--- a/libnixt/meson.build
+++ b/libnixt/meson.build
@@ -40,7 +40,12 @@ libnixt_test_exe = executable(
     dependencies: [ gtest_main, nixt ]
 )
 
-subdir('tools')
+nixt_decode = executable(
+    'nixt-decode',
+    'tools/nixt-decode.cpp',
+    dependencies: [ nixt ],
+    install: true
+)
 
 test(
     'unit/libnixt',
diff --git a/libnixt/tools/meson.build b/libnixt/tools/meson.build
deleted file mode 100644
index cd4b50ae0..000000000
--- a/libnixt/tools/meson.build
+++ /dev/null
@@ -1 +0,0 @@
-subdir('nixt-decode')
diff --git a/libnixt/tools/nixt-decode/Main.cpp b/libnixt/tools/nixt-decode.cpp
similarity index 50%
rename from libnixt/tools/nixt-decode/Main.cpp
rename to libnixt/tools/nixt-decode.cpp
index 8345486df..d2485e427 100644
--- a/libnixt/tools/nixt-decode/Main.cpp
+++ b/libnixt/tools/nixt-decode.cpp
@@ -3,7 +3,24 @@
 #include "nixt/InitEval.h"
 #include "nixt/PtrPool.h"
 
-int main() {
+namespace {
+
+// --eval, -e
+// Should we perform eval?
+bool Eval = false;
+
+void parseArgs(int Argc, const char *Argv[]) {
+  for (int I = 0; I < Argc; I++) {
+    std::string_view Arg(Argv[I]);
+    if (Arg == "--eval" || Arg == "-e")
+      Eval = true;
+  }
+}
+
+} // namespace
+
+int main(int Argc, const char *Argv[]) {
+  parseArgs(Argc, Argv);
   nixt::initEval();
   std::unique_ptr<nix::EvalState> State(
       new nix::EvalState{{}, nix::openStore("dummy://")});
@@ -24,7 +41,18 @@ int main() {
 
   auto *AST = nixt::deserializeHookable(Data, Ctx, Pool, VMap, EMap);
 
-  AST->show(State->symbols, std::cout);
+  if (Eval) {
+    try {
+      AST->bindVars(*State, State->staticBaseEnv);
+      nix::Value V;
+      State->eval(AST, V);
+      V.print(State->symbols, std::cout);
+    } catch (nix::BaseError &E) {
+      std::cerr << E.what() << "\n";
+    }
+  } else {
+    AST->show(State->symbols, std::cout);
+  }
 
   return 0;
 }
diff --git a/libnixt/tools/nixt-decode/meson.build b/libnixt/tools/nixt-decode/meson.build
deleted file mode 100644
index 4f066f78e..000000000
--- a/libnixt/tools/nixt-decode/meson.build
+++ /dev/null
@@ -1,5 +0,0 @@
-executable('nixt-decode',
-    'Main.cpp',
-    install: true,
-    dependencies: [ nixt ]
-)