From 6bc50885162249a5466d6c2229a6776dd54ffe44 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Luis=20Lafuente?= <jose.lafuente@tweag.io>
Date: Sun, 25 Feb 2024 00:28:04 +0100
Subject: [PATCH] C API: add tests for external values

---
 doc/external-api/README.md             |  2 +-
 src/libexpr/c/nix_api_expr_internal.h  | 15 +++++
 src/libexpr/c/nix_api_external.cc      | 15 -----
 src/libexpr/c/nix_api_value.h          |  2 +-
 tests/unit/libexpr/nix_api_external.cc | 83 ++++++++++++++++++++++++++
 5 files changed, 100 insertions(+), 17 deletions(-)
 create mode 100644 tests/unit/libexpr/nix_api_external.cc

diff --git a/doc/external-api/README.md b/doc/external-api/README.md
index e9ca25ab6d08..24118f9f05eb 100644
--- a/doc/external-api/README.md
+++ b/doc/external-api/README.md
@@ -82,7 +82,7 @@ will increment the argument if it is an integer and throw an error otherwise.
 void increment(void* user_data, nix_c_context* ctx, EvalState* state, Value** args, Value* v) {
     nix_value_force(NULL, state, args[0]);
     if (nix_get_type(NULL, args[0]) == NIX_TYPE_INT) {
-      nix_set_int(NULL, v, nix_get_int(NULL, args[0]) + 1);
+      nix_init_int(NULL, v, nix_get_int(NULL, args[0]) + 1);
     } else {
       nix_set_err_msg(ctx, NIX_ERR_UNKNOWN, "First argument should be an integer.");
     }
diff --git a/src/libexpr/c/nix_api_expr_internal.h b/src/libexpr/c/nix_api_expr_internal.h
index e116af165cf6..352ac496f1b1 100644
--- a/src/libexpr/c/nix_api_expr_internal.h
+++ b/src/libexpr/c/nix_api_expr_internal.h
@@ -14,4 +14,19 @@ struct BindingsBuilder
     nix::BindingsBuilder builder;
 };
 
+struct nix_string_return
+{
+    std::string str;
+};
+
+struct nix_printer
+{
+    std::ostream & s;
+};
+
+struct nix_string_context
+{
+    nix::NixStringContext & ctx;
+};
+
 #endif // NIX_API_EXPR_INTERNAL_H
diff --git a/src/libexpr/c/nix_api_external.cc b/src/libexpr/c/nix_api_external.cc
index 3af4af4d4611..c237cfb708b8 100644
--- a/src/libexpr/c/nix_api_external.cc
+++ b/src/libexpr/c/nix_api_external.cc
@@ -20,21 +20,6 @@
 #include "gc_cpp.h"
 #endif
 
-struct nix_string_return
-{
-    std::string str;
-};
-
-struct nix_printer
-{
-    std::ostream & s;
-};
-
-struct nix_string_context
-{
-    nix::NixStringContext & ctx;
-};
-
 void nix_set_string_return(nix_string_return * str, const char * c)
 {
     str->str = c;
diff --git a/src/libexpr/c/nix_api_value.h b/src/libexpr/c/nix_api_value.h
index 27027caf0d30..a9a640231fbd 100644
--- a/src/libexpr/c/nix_api_value.h
+++ b/src/libexpr/c/nix_api_value.h
@@ -52,7 +52,7 @@ typedef class ListBuilder ListBuilder;
  * @ingroup primops
  *
  * Owned by the GC
- * @see nix_alloc_primop, nix_set_primop
+ * @see nix_alloc_primop, nix_init_primop
  */
 typedef struct PrimOp PrimOp;
 /** @brief External Value
diff --git a/tests/unit/libexpr/nix_api_external.cc b/tests/unit/libexpr/nix_api_external.cc
new file mode 100644
index 000000000000..5f5353b049b1
--- /dev/null
+++ b/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));
+}
+}