stdcoroutine-2: Migrate production entry points from Boost.Coroutine to C++20 coroutines

[pratikmankawde]

High Level Overview of Change

Migrate all production postCoro() call sites to postCoroTask() using C++20 coroutine lambdas, as part of the Boost.Coroutine → std coroutines migration. This eliminates the Context::coro field and replaces the RipplePathFind yield/post/resume pattern with a simpler std::condition_variable approach.

Context of Change

This is Milestone 2 of the Boost.Coroutine → C++20 coroutines migration. Milestone 1 (pratik/std-coro/add-coroutine-primitives) introduced the new coroutine primitives (CoroTask<T>, CoroTaskRunner, JobQueueAwaiter, postCoroTask()). This milestone migrates all production code to use them.

• Milestone 1 (pratik/std-coro/add-coroutine-primitives): Added CoroTask<T>, CoroTaskRunner, JobQueueAwaiter, postCoroTask()
• Milestone 2 (pratik/std-coro/migrate-entry-points): Migrated all production entry points
• Milestone 3 (pratik/std-coro/migrate-test-code): Migrated all test code
• Milestone 4 (this PR): Delete old code and build dependencies

Key design decision: Rather than "coloring" the entire processSession → processRequest → doCommand → callMethod → doRipplePathFind call chain as coroutines (which C++20 stackless coroutines would require for co_await to work at any depth), we replace RipplePathFind's yield()/post()/resume() pattern with a local std::condition_variable that blocks the thread until path-finding completes. This is correct, simple, and bounded by existing path-finding timeouts.

Since context.coro has no remaining readers after this change, the field is removed entirely from RPC::Context.

Type of Change

• Refactor (non-breaking change that only restructures code)

API Impact

• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)

Before / After

Entry points (ServerHandler::onRequest, onWSMessage, GRPCServer::CallData::process):

// Before:
m_jobQueue.postCoro(jtCLIENT_RPC, "RPC-Client",
    [this, session](std::shared_ptr<JobQueue::Coro> coro) {
        processSession(session, coro);
    });

// After:
m_jobQueue.postCoroTask(jtCLIENT_RPC, "RPC-Client",
    [this, session](auto) -> CoroTask<void> {
        processSession(session);
        co_return;
    });

RipplePathFind handler:

// Before: yield/post/resume via Boost.Coroutine
jvResult = context.app.getPathRequests().makeLegacyPathRequest(
    request,
    [&context]() {
        std::shared_ptr<JobQueue::Coro> coroCopy{context.coro};
        if (!coroCopy->post())
            coroCopy->resume();
    },
    context.consumer, lpLedger, context.params);
if (request) {
    context.coro->yield();
    jvResult = request->doStatus(context.params);
}

// After: condition_variable blocking wait
std::mutex mtx;
std::condition_variable cv;
bool pathDone = false;
jvResult = context.app.getPathRequests().makeLegacyPathRequest(
    request,
    [&]() { { std::lock_guard lk(mtx); pathDone = true; } cv.notify_one(); },
    context.consumer, lpLedger, context.params);
if (request) {
    std::unique_lock lk(mtx);
    cv.wait(lk, [&] { return pathDone; });
    jvResult = request->doStatus(context.params);
}

Future Tasks

• Milestone 3: Migrate old coroutine tests (Coroutine_test.cpp, JobQueue_test.cpp) to postCoroTask
• Milestone 4: Delete Coro.ipp, remove old Coro class and postCoro() from JobQueue.h, remove Boost.Coroutine from CMake/Conan dependencies

[codecov]

Codecov Report

❌ Patch coverage is 78.46890% with 45 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.8%. Comparing base (65e63eb) to head (666cafc).
⚠️ Report is 3 commits behind head on pratik/Swtich-to-std-coroutines.

Files with missing lines	Patch %	Lines
include/xrpl/core/CoroTaskRunner.ipp	80.3%	14 Missing ⚠️
src/xrpld/rpc/handlers/RipplePathFind.cpp	0.0%	9 Missing ⚠️
include/xrpl/core/CoroTask.h	93.1%	5 Missing ⚠️
src/xrpld/app/main/GRPCServer.cpp	0.0%	4 Missing ⚠️
include/xrpl/core/JobQueue.h	87.5%	2 Missing ⚠️
include/xrpl/core/JobQueueAwaiter.h	80.0%	2 Missing ⚠️
src/libxrpl/nodestore/backend/MemoryFactory.cpp	33.3%	2 Missing ⚠️
src/libxrpl/nodestore/backend/NuDBFactory.cpp	66.7%	2 Missing ⚠️
src/libxrpl/nodestore/backend/NullFactory.cpp	0.0%	2 Missing ⚠️
src/libxrpl/nodestore/backend/RocksDBFactory.cpp	71.4%	2 Missing ⚠️
... and 1 more

Additional details and impacted files

@@                       Coverage Diff                        @@
##           pratik/Swtich-to-std-coroutines   #6423    +/-   ##
================================================================
  Coverage                             79.8%   79.8%            
================================================================
  Files                                  848     851     +3     
  Lines                                67763   67921   +158     
  Branches                              7578    7555    -23     
================================================================
+ Hits                                 54077   54218   +141     
- Misses                               13686   13703    +17     

Files with missing lines	Coverage Δ
include/xrpl/nodestore/Backend.h	14.3% <ø> (ø)
src/libxrpl/nodestore/DatabaseRotatingImp.cpp	63.9% <100.0%> (ø)
src/xrpld/app/main/Application.cpp	70.0% <ø> (ø)
src/xrpld/app/main/GRPCServer.h	100.0% <ø> (ø)
src/xrpld/rpc/ServerHandler.h	100.0% <ø> (ø)
src/xrpld/rpc/detail/ServerHandler.cpp	87.6% <100.0%> (-0.2%)	⬇️
src/libxrpl/nodestore/DatabaseNodeImp.cpp	39.5% <50.0%> (+4.6%)	⬆️
include/xrpl/core/JobQueue.h	92.9% <87.5%> (-7.1%)	⬇️
include/xrpl/core/JobQueueAwaiter.h	80.0% <80.0%> (ø)
src/libxrpl/nodestore/backend/MemoryFactory.cpp	67.6% <33.3%> (-0.5%)	⬇️
... and 7 more

... and 5 files with indirect coverage changes

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