From af8ec168c44d50a3e3fe20e8cdd2a8e7f618677e Mon Sep 17 00:00:00 2001
From: Nik Delgado <84356491+nikdelgado@users.noreply.github.com>
Date: Fri, 26 Dec 2025 00:01:58 -0700
Subject: [PATCH] implement .begin() and .end() for etl::optional (#1246)

Co-authored-by: nikdelgado <nikdelgado@icloud.com>
---
 include/etl/optional.h | 38 +++++++++++++++++++
 test/test_optional.cpp | 84 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 122 insertions(+)

diff --git a/include/etl/optional.h b/include/etl/optional.h
index 3b565c5b..ec998479 100644
--- a/include/etl/optional.h
+++ b/include/etl/optional.h
@@ -1326,6 +1326,8 @@ namespace etl
   public:
 
     typedef T value_type;
+    typedef T* iterator;
+    typedef const T* const_iterator;
 
 #if ETL_USING_CPP11
     //***************************************************************************
@@ -1698,6 +1700,42 @@ namespace etl
       return *this;
     }
 #endif
+
+    //***************************************************************************
+    /// Returns an iterator to the beginning of the optional.
+    //***************************************************************************
+    ETL_CONSTEXPR20_STL
+    iterator begin() ETL_NOEXCEPT
+    {
+      return this->has_value() ? this->operator->() : ETL_NULLPTR;
+    }
+
+    //***************************************************************************
+    /// Returns a const iterator to the beginning of the optional.
+    //***************************************************************************
+    ETL_CONSTEXPR20_STL
+    const_iterator begin() const ETL_NOEXCEPT
+    {
+      return this->has_value() ? this->operator->() : ETL_NULLPTR;
+    }
+
+    //***************************************************************************
+    /// Returns an iterator to the end of the optional.
+    //***************************************************************************
+    ETL_CONSTEXPR20_STL
+    iterator end() ETL_NOEXCEPT
+    {
+      return this->has_value() ? this->operator->() + 1 : ETL_NULLPTR;
+    }
+
+    //***************************************************************************
+    /// Returns a const iterator to the end of the optional.
+    //***************************************************************************
+    ETL_CONSTEXPR20_STL
+    const_iterator end() const ETL_NOEXCEPT
+    {
+      return this->has_value() ? this->operator->() + 1 : ETL_NULLPTR;
+    }
   };
 
 #include "private/diagnostic_uninitialized_push.h"
diff --git a/test/test_optional.cpp b/test/test_optional.cpp
index 99d8a312..6ca762a9 100644
--- a/test/test_optional.cpp
+++ b/test/test_optional.cpp
@@ -1034,5 +1034,89 @@ namespace
       CHECK_EQUAL(1, (*opt3)[0]);
       CHECK_EQUAL(20, (*opt3)[1]);
     }
+
+    //*************************************************************************
+    TEST(test_begin_end_with_value)
+    {
+      etl::optional<int> opt = 4;
+
+      CHECK(opt.begin() != opt.end());
+      CHECK_EQUAL(4, *opt.begin());
+      CHECK_EQUAL(1, std::distance(opt.begin(), opt.end()));
+    }
+
+    TEST(test_begin_end_empty)
+    {
+      etl::optional<int> opt;
+
+      CHECK(opt.begin() == ETL_NULLPTR);
+      CHECK(opt.begin() == opt.end());
+    }
+
+    TEST(test_const_begin_end_with_value)
+    {
+      const etl::optional<int> opt = 4;
+
+      CHECK(opt.begin() != opt.end());
+      CHECK_EQUAL(4, *opt.begin());
+      CHECK_EQUAL(1, std::distance(opt.begin(), opt.end()));
+    }
+
+    TEST(test_const_begin_end_empty)
+    {
+      const etl::optional<int> opt;
+
+      CHECK(opt.begin() == ETL_NULLPTR);
+      CHECK(opt.begin() == opt.end());
+    }
+
+    TEST(range_based_for_loop_with_value)
+    {
+      etl::optional<int> opt = 4;
+
+      int sum = 0;
+      for (int value : opt)
+      {
+        sum += value;
+      }
+
+      CHECK_EQUAL(4, sum);
+    }
+
+    TEST(range_based_for_loop_empty)
+    {
+      etl::optional<int> opt;
+
+      int sum = 0;
+      for (int value : opt)
+      {
+        sum += value;
+      }
+
+      CHECK_EQUAL(0, sum);
+    }
+
+    TEST(test_range_based_for_loop_non_trivial)
+    {
+      etl::optional<Data> opt = Data("TEST");
+      int count= 0;
+
+      for (const Data& value : opt)
+      {
+        CHECK_EQUAL(Data("TEST"), value);
+        count++;
+      }
+
+      CHECK_EQUAL(1, count);
+    }
+
+    TEST(test_begin_end_modify_value)
+    {
+      etl::optional<int> opt = 4;
+
+      *opt.begin() = 42;
+
+      CHECK_EQUAL(42, *opt);
+    }
   }
 }