From 75283c35f62ff3b1bc9c579e0fe865ed90ea36d1 Mon Sep 17 00:00:00 2001
From: Alfi Maulana <alfi.maulana.f@gmail.com>
Date: Tue, 26 Dec 2023 22:39:08 +0700
Subject: [PATCH] feat: add `nil` function

---
 include/errors/error.hpp | 8 ++++++++
 src/error.cpp            | 5 +++++
 test/error_test.cpp      | 2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/errors/error.hpp b/include/errors/error.hpp
index c664762..4b58ed5 100644
--- a/include/errors/error.hpp
+++ b/include/errors/error.hpp
@@ -54,6 +54,7 @@ class Error {
   explicit operator bool() const;
 
   friend Error make(const std::string& msg);
+  friend const Error& nil();
 
   /**
    * @brief Writes the string representation of an error object to the given
@@ -83,4 +84,11 @@ class Error {
  */
 Error make(const std::string& msg);
 
+
+/**
+ * @brief Gets a constant reference of an empty error.
+ * @return A constant reference of an empty error.
+ */
+const Error& nil();
+
 }  // namespace error
diff --git a/src/error.cpp b/src/error.cpp
index 40d756f..5003c86 100644
--- a/src/error.cpp
+++ b/src/error.cpp
@@ -23,4 +23,9 @@ Error make(const std::string& msg) {
   return Error(std::make_shared<const std::string>(msg));
 }
 
+const Error& nil() {
+  static const Error err(nullptr);
+  return err;
+}
+
 }  // namespace error
diff --git a/test/error_test.cpp b/test/error_test.cpp
index 6b8b1a4..c544fc3 100644
--- a/test/error_test.cpp
+++ b/test/error_test.cpp
@@ -9,7 +9,7 @@ TEST_CASE("Error Construction") {
 }
 
 TEST_CASE("Empty Error Construction") {
-  const errors::Error err;
+  const auto err = errors::nil();
   REQUIRE_FALSE(err);
   REQUIRE(err.message() == "no error");
 }