LockedPtr::and_then introduced

[sankurm]

Monadic interfaces help write functional code by supporting transform, and_then and or_else. This PR is to support and_then.

This makes the following possible.

auto maybe_number = [](const LockedPtr<std::string>& lp) -> std::optional<int> {
    int result{};
    auto [ptr, ec] = std::from_chars(lp->data(), lp->data() + lp->size(), result);
    if (ec == std::errc::invalid_argument || ec == std::errc::result_out_of_range)
    {
        return std::nullopt;
    }
    else
    {
        return result;
    }
};

auto output = [](int n) {
    std::cout << n << '\n';
    return std::nullopt;
};

Synchronized<std::string> synced_num{"42"};
Synchronized<std::string> synced_non_num{"GitHub"};

auto ignore1 = synced_num.lock()
                         .and_then(maybe_number)
                         .and_then(output);         //Prints 42

auto ignore2 = synced_non_num.lock()
                             .and_then(maybe_number)
                             .and_then(output);    //No output as this is not executed as string is not a number

[github-actions]

The created documentation from the pull request is available at: docu-html

[Copilot]

Pull request overview

Adds LockedPtr::and_then for optional-based monadic chaining.

Changes:

• Adds optional detection support.
• Implements four value-category overloads.
• Adds tests for success, empty, and null cases.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
score/concurrency/type_traits.h	Adds optional type detection.
score/concurrency/locked_ptr.h	Implements and_then.
score/concurrency/locked_ptr_test.cpp	Tests the new overloads.

Suppressed comments (6)

score/concurrency/locked_ptr.h:227

• Ret preserves cv/reference qualifiers, so this overload rejects callables returning const optional<T> or optional<T>&, unlike score::cpp::optional::and_then. Decay the invocation result so all supported optional return forms produce an optional value.

              typename Ret = std::invoke_result_t<Func, const LockedPtr&>,

score/concurrency/locked_ptr.h:248

• Ret preserves cv/reference qualifiers, so this overload rejects callables returning const optional<T> or optional<T>&, unlike score::cpp::optional::and_then. Decay the invocation result so all supported optional return forms produce an optional value.

              typename Ret = std::invoke_result_t<Func, LockedPtr>,

score/concurrency/locked_ptr.h:269

• Ret preserves cv/reference qualifiers, so this overload rejects callables returning const optional<T> or optional<T>&, unlike score::cpp::optional::and_then. Decay the invocation result so all supported optional return forms produce an optional value.

              typename Ret = std::invoke_result_t<Func, const LockedPtr&>,

score/concurrency/locked_ptr_test.cpp:53

• This namespace-scope lambda object is a mutable global. Repository style requires fixed namespace-scope values to be const/constexpr and k-prefixed (docs/cpp-style-guide.md:29); use a constant or named helper function and update its call sites.

auto value_if_positive = [](LPtr2IntW& lp) -> score::cpp::optional<int> {

score/concurrency/locked_ptr_test.cpp:61

• This namespace-scope lambda object is a mutable global. Repository style requires fixed namespace-scope values to be const/constexpr and k-prefixed (docs/cpp-style-guide.md:29); use a constant or named helper function and update its call sites.

auto cvalue_if_positive = [](const LPtr2IntW& lp) -> score::cpp::optional<int> {

score/concurrency/locked_ptr_test.cpp:69

• This namespace-scope lambda object is a mutable global. Repository style requires fixed namespace-scope values to be const/constexpr and k-prefixed (docs/cpp-style-guide.md:29); use a constant or named helper function and update its call sites.

auto opt_move_get = [](LPtr2IntW lp) -> score::cpp::optional<IntWrapper*> {

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[github-actions]

Documentation preview for this pull request is available at:
pr-458: https://eclipse-score.github.io/baselibs/pr-458/