From 8a36d2d8a77dc3f3214ac6f7fd67cbe15ec6c706 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 19 Nov 2024 18:23:05 +0100
Subject: [PATCH] Add EvalState::getBuiltins

---
 src/libexpr-test-support/tests/libexpr.hh |  6 ++++++
 src/libexpr-tests/eval.cc                 | 25 ++++++++++++++++++++++-
 src/libexpr/eval.cc                       |  8 +++++++-
 src/libexpr/eval.hh                       |  6 ++++++
 4 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/src/libexpr-test-support/tests/libexpr.hh b/src/libexpr-test-support/tests/libexpr.hh
index 045607e87..095ea1d0e 100644
--- a/src/libexpr-test-support/tests/libexpr.hh
+++ b/src/libexpr-test-support/tests/libexpr.hh
@@ -40,6 +40,12 @@ namespace nix {
                 return v;
             }
 
+            Value * maybeThunk(std::string input, bool forceValue = true) {
+                Expr * e = state.parseExprFromString(input, state.rootPath(CanonPath::root));
+                assert(e);
+                return e->maybeThunk(state, state.baseEnv);
+            }
+
             Symbol createSymbol(const char * value) {
                 return state.symbols.create(value);
             }
diff --git a/src/libexpr-tests/eval.cc b/src/libexpr-tests/eval.cc
index 93d3f658f..61f6be0db 100644
--- a/src/libexpr-tests/eval.cc
+++ b/src/libexpr-tests/eval.cc
@@ -138,4 +138,27 @@ TEST(nix_isAllowedURI, non_scheme_colon) {
     ASSERT_FALSE(isAllowedURI("https://foo/bar:baz", allowed));
 }
 
-} // namespace nix
\ No newline at end of file
+class EvalStateTest : public LibExprTest {};
+
+TEST_F(EvalStateTest, getBuiltins_ok) {
+    auto evaled = maybeThunk("builtins");
+    auto & builtins = state.getBuiltins();
+    ASSERT_TRUE(builtins.type() == nAttrs);
+    ASSERT_EQ(evaled, &builtins);
+}
+
+TEST_F(EvalStateTest, getBuiltin_ok) {
+    auto & builtin = state.getBuiltin("toString");
+    ASSERT_TRUE(builtin.type() == nFunction);
+    // FIXME
+    // auto evaled = maybeThunk("builtins.toString");
+    // ASSERT_EQ(evaled, &builtin);
+    auto & builtin2 = state.getBuiltin("true");
+    ASSERT_EQ(state.forceBool(builtin2, noPos, "in unit test"), true);
+}
+
+TEST_F(EvalStateTest, getBuiltin_fail) {
+    ASSERT_THROW(state.getBuiltin("nonexistent"), EvalError);
+}
+
+} // namespace nix
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index dd14f485e..b1b7a0fe6 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -523,13 +523,19 @@ Value * EvalState::addPrimOp(PrimOp && primOp)
 }
 
 
+Value & EvalState::getBuiltins()
+{
+    return *baseEnv.values[0];
+}
+
+
 Value & EvalState::getBuiltin(const std::string & name)
 {
     auto it = baseEnv.values[0]->attrs()->get(symbols.create(name));
     if (it)
         return *it->value;
     else
-        throw EvalError("builtin '%1%' not found", name);
+        error<EvalError>("builtin '%1%' not found", name).debugThrow();
 }
 
 
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 01c725930..a14e88f0e 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -630,6 +630,12 @@ public:
      */
     Value & getBuiltin(const std::string & name);
 
+    /**
+     * Retrieve the `builtins` attrset, equivalent to evaluating the reference `builtins`.
+     * Always returns an attribute set value.
+     */
+    Value & getBuiltins();
+
     struct Doc
     {
         Pos pos;