perf(amp): avoid fibers in future adapter

[simPod]

Context

AmpFutureAdapter created an AMPHP Fiber for every promise continuation and aggregate. Wide GraphQL result graphs therefore retained many Fiber states and event-loop callbacks even when the underlying Futures only represented batched work.

Decision

Compose and aggregate Futures through map() and catch() callbacks, settling one DeferredFuture while retaining Promise fulfillment, rejection, and nested-Future flattening semantics.

Consequences

• Reduces per-field allocation and event-loop scheduling for wide asynchronous result graphs.
• Preserves deferred completion for genuinely asynchronous resolvers.
• Adds coverage for nested Future fulfillment/recovery, fulfillment errors, aggregate key preservation, and aggregate rejection.

Benchmark

On the same wide GraphQL result graph with 838 parent objects and three Future-backed fields:

Adapter	CPU time	Peak memory
Synchronous adapter	1.48s	122MB
Existing AMPHP adapter	2.11s	274MB
This change	1.67-1.70s	149MB

Relative to the existing AMPHP adapter, this reduces CPU time by about 19% and peak memory by about 46%. The remaining overhead compared with the synchronous adapter is about 13-15% CPU and 22% memory.

[Copilot]

Pull request overview

This PR refactors AmpFutureAdapter to avoid creating a new AMPHP Fiber for each promise continuation and aggregate operation by composing Futures via map()/catch() and settling a single DeferredFuture instead. This targets lower allocation and event-loop scheduling overhead for wide asynchronous GraphQL result graphs.

Changes:

• Rework AmpFutureAdapter::then() and AmpFutureAdapter::all() to compose/aggregate futures without Amp\async() / Amp\Future\await().
• Add tests for future unwrapping behavior, rejection handling, key preservation in all(), and aggregate rejection.
• Document the performance fix in CHANGELOG.md.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tests/Executor/Promise/AmpFutureAdapterTest.php	Adds/updates coverage for nested-future unwrapping, rejection semantics, key preservation, and aggregate rejection behavior.
src/Executor/Promise/Adapter/AmpFutureAdapter.php	Refactors then()/all() to use DeferredFuture + map()/catch() instead of spawning fibers via async().
CHANGELOG.md	Notes the behavioral/performance fix for the Amp adapter under “Unreleased”.

Comments suppressed due to low confidence (2)

tests/Executor/Promise/AmpFutureAdapterTest.php:185

• AmpFutureAdapter::then() invokes the rejection callback with the rejection Throwable. This zero-argument closure will throw an ArgumentCountError when called, preventing the test from asserting the recovered value.

        $resultPromise = $ampAdapter->then(
            $promise,
            null,
            static fn (): Future => $deferred->getFuture()
        );

tests/Executor/Promise/AmpFutureAdapterTest.php:100

• AmpFutureAdapter::then() passes the fulfillment value and rejection reason into the respective callbacks. Both callbacks here declare no parameters, so the test will fail with ArgumentCountError rather than asserting the intended RuntimeException behavior.

            static function (): void {
                throw new \RuntimeException('fulfillment failed');
            },
            static fn (): string => 'recovered'

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.