C API: add tests for external values

tests/unit/libexpr/nix_api_external.cc

@@ -0,0 +1,83 @@
+#include "nix_api_store.h"
+#include "nix_api_store_internal.h"
+#include "nix_api_util.h"
+#include "nix_api_util_internal.h"
+#include "nix_api_expr.h"
+#include "nix_api_expr_internal.h"
+#include "nix_api_value.h"
+#include "nix_api_external.h"
+#include "tests/nix_api_store.hh"
+
+#include <string>
+#include <gtest/gtest.h>
+
+namespace nixC {
+
+class MyExternalValueDesc : public NixCExternalValueDesc
+{
+public:
+    MyExternalValueDesc(int x)
+        : _x(x)
+    {
+        print = print_function;
+        showType = show_type_function;
+        typeOf = type_of_function;
+    }
+
+private:
+    int _x;
+    static void print_function(void * self, nix_printer * printer) {}
+
+    static void show_type_function(void * self, nix_string_return * res) {}
+
+    static void type_of_function(void * self, nix_string_return * res)
+    {
+        std::cout << self << std::endl;
+        MyExternalValueDesc * obj = static_cast<MyExternalValueDesc *>(self);
+
+        std::string type_string = "nix-external<MyExternalValueDesc( ";
+        type_string += std::to_string(obj->_x);
+        type_string += " )>";
+        res->str = &*type_string.begin();
+    }
+};
+
+class nix_api_external_test : public nix_api_store_test
+{
+public:
+    nix_api_external_test()
+    {
+        state = nix_state_create(nullptr, nullptr, store);
+        value = nix_alloc_value(nullptr, state);
+    }
+    ~nix_api_external_test()
+    {
+        nix_gc_decref(nullptr, value);
+        nix_state_free(state);
+    }
+
+    EvalState * state;
+    Value * value;
+};
+
+TEST_F(nix_api_external_test, nix_expr_eval_from_string)
+{
+    MyExternalValueDesc * external = new MyExternalValueDesc(42);
+    ExternalValue * val = nix_create_external_value(ctx, external, external);
+    nix_init_external(nullptr, value, val);
+
+    EvalState * stateResult = nix_state_create(nullptr, nullptr, store);
+    Value * valueResult = nix_alloc_value(nullptr, stateResult);
+
+    EvalState * stateFn = nix_state_create(nullptr, nullptr, store);
+    Value * valueFn = nix_alloc_value(nullptr, stateFn);
+
+    nix_expr_eval_from_string(nullptr, state, "builtins.typeOf", ".", valueFn);
+
+    ASSERT_EQ(NIX_TYPE_EXTERNAL, nix_get_type(nullptr, value));
+
+    nix_value_call(ctx, state, valueFn, value, valueResult);
+
+    ASSERT_STREQ("nix-external<MyExternalValueDesc( 42 )>", nix_get_string(nullptr, valueResult));
+}
+}