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Improve memory consumption by only passing resolver args to resolver and canceller if callback requires them #113

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Apr 24, 2018
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Improve memory consumption by only passing resolver args to resolver and canceller if callback requires them #113

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40 changes: 29 additions & 11 deletions src/Promise.php
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Original file line number Diff line number Diff line change
Expand Up @@ -221,18 +221,36 @@ private function extract($promise)

private function call(callable $callback)
{
// Use reflection to inspect number of arguments expected by this callback.
// We did some careful benchmarking here: Using reflection to avoid unneeded
// function arguments is actually faster than blindly passing them.
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The reason for it being faster isn't avoiding the arguments being passed, but rather the three closure creations that are saved.

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@kelunik Do you feel that this helps with understanding the motivation for this change? If so, I encourage you to file this as a new documentation PR and maybe back this with some numbers :shipit:

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@clue I think the motivation is completely covered by the circular references, the rest is just additional background on the performance of the patch. It's not super important to change, just a minor note I had while reading.

// Also, this helps avoiding unnecessary function arguments in the call stack
// if the callback creates an Exception (creating garbage cycles).
if (is_array($callback)) {
$ref = new \ReflectionMethod($callback[0], $callback[1]);
} elseif (is_object($callback) && !$callback instanceof \Closure) {
$ref = new \ReflectionMethod($callback, '__invoke');
} else {
$ref = new \ReflectionFunction($callback);
}
$args = $ref->getNumberOfParameters();

try {
$callback(
function ($value = null) {
$this->resolve($value);
},
function ($reason = null) {
$this->reject($reason);
},
function ($update = null) {
$this->notify($update);
}
);
if ($args === 0) {
$callback();
} else {
$callback(
function ($value = null) {
$this->resolve($value);
},
function ($reason = null) {
$this->reject($reason);
},
function ($update = null) {
$this->notify($update);
}
);
}
} catch (\Throwable $e) {
$this->reject($e);
} catch (\Exception $e) {
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12 changes: 12 additions & 0 deletions tests/PromiseTest.php
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Expand Up @@ -48,6 +48,18 @@ public function shouldRejectIfResolverThrowsException()
->then($this->expectCallableNever(), $mock);
}

/** @test */
public function shouldRejectWithoutCreatingGarbageCyclesIfResolverThrowsException()
{
gc_collect_cycles();
$promise = new Promise(function () {
throw new \Exception('foo');
});
unset($promise);

$this->assertSame(0, gc_collect_cycles());
}

/** @test */
public function shouldFulfillIfFullfilledWithSimplePromise()
{
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27 changes: 21 additions & 6 deletions tests/PromiseTest/CancelTestTrait.php
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Expand Up @@ -14,15 +14,30 @@ abstract public function getPromiseTestAdapter(callable $canceller = null);
/** @test */
public function cancelShouldCallCancellerWithResolverArguments()
{
$mock = $this->createCallableMock();
$mock
->expects($this->once())
->method('__invoke')
->with($this->isType('callable'), $this->isType('callable'), $this->isType('callable'));
$args = null;
$adapter = $this->getPromiseTestAdapter(function ($resolve, $reject, $notify) use (&$args) {
$args = func_get_args();
});

$adapter = $this->getPromiseTestAdapter($mock);
$adapter->promise()->cancel();

$this->assertCount(3, $args);
$this->assertTrue(is_callable($args[0]));
$this->assertTrue(is_callable($args[1]));
$this->assertTrue(is_callable($args[2]));
}

/** @test */
public function cancelShouldCallCancellerWithoutArgumentsIfNotAccessed()
{
$args = null;
$adapter = $this->getPromiseTestAdapter(function () use (&$args) {
$args = func_num_args();
});

$adapter->promise()->cancel();

$this->assertSame(0, $args);
}

/** @test */
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