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Mark array_filter(), array_map(), array_reduce() and PHP 8.4 array_find/array_any/array_all as pure in function metadata #5580

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Mark array_filter(), array_map(), array_reduce() and PHP 8.4 array_find/array_any/array_all as pure in function metadata #5580

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a09ab3a
Mark `array_filter()`, `array_map()`, `array_reduce()` and PHP 8.4 `a…
VincentLanglet May 1, 2026
bc9200f
Implement @phpstan-pure-unless-callable-is-impure tag and mark callba…
phpstan-bot May 1, 2026
e562794
Do not treat @phpstan-pure-unless-callable-is-impure as unconditional…
phpstan-bot May 1, 2026
0953cfc
Store pureUnlessCallableIsImpure as array of parameter names instead …
phpstan-bot May 1, 2026
ce47eba
Remove pureUnlessCallableIsImpure from function metadata
phpstan-bot May 1, 2026
0d86fb8
Remove pureUnlessCallableIsImpure implementation, rely on existing @p…
phpstan-bot May 1, 2026
eba6f20
Remove getFunctionPurityFromMetadata, use lint directives in array-fi…
phpstan-bot May 2, 2026
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7 changes: 7 additions & 0 deletions bin/functionMetadata_original.php
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Expand Up @@ -20,6 +20,8 @@
'apcu_key_info' => ['hasSideEffects' => true],
'apcu_sma_info' => ['hasSideEffects' => true],
'apcu_store' => ['hasSideEffects' => true],
'array_all' => ['hasSideEffects' => false],
'array_any' => ['hasSideEffects' => false],
'array_change_key_case' => ['hasSideEffects' => false],
'array_chunk' => ['hasSideEffects' => false],
'array_column' => ['hasSideEffects' => false],
Expand All @@ -32,6 +34,9 @@
'array_diff_ukey' => ['hasSideEffects' => false],
'array_fill' => ['hasSideEffects' => false],
'array_fill_keys' => ['hasSideEffects' => false],
'array_filter' => ['hasSideEffects' => false],
'array_find' => ['hasSideEffects' => false],
'array_find_key' => ['hasSideEffects' => false],
'array_flip' => ['hasSideEffects' => false],
'array_intersect' => ['hasSideEffects' => false],
'array_intersect_assoc' => ['hasSideEffects' => false],
Expand All @@ -42,13 +47,15 @@
'array_key_last' => ['hasSideEffects' => false],
'array_key_exists' => ['hasSideEffects' => false],
'array_keys' => ['hasSideEffects' => false],
'array_map' => ['hasSideEffects' => false],
'array_merge' => ['hasSideEffects' => false],
'array_merge_recursive' => ['hasSideEffects' => false],
'array_pad' => ['hasSideEffects' => false],
'array_pop' => ['hasSideEffects' => true],
'array_product' => ['hasSideEffects' => false],
'array_push' => ['hasSideEffects' => true],
'array_rand' => ['hasSideEffects' => false],
'array_reduce' => ['hasSideEffects' => false],
'array_replace' => ['hasSideEffects' => false],
'array_replace_recursive' => ['hasSideEffects' => false],
'array_reverse' => ['hasSideEffects' => false],
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7 changes: 7 additions & 0 deletions resources/functionMetadata.php
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Expand Up @@ -725,6 +725,8 @@
'apcu_key_info' => ['hasSideEffects' => true],
'apcu_sma_info' => ['hasSideEffects' => true],
'apcu_store' => ['hasSideEffects' => true],
'array_all' => ['hasSideEffects' => false],
'array_any' => ['hasSideEffects' => false],
'array_change_key_case' => ['hasSideEffects' => false],
'array_chunk' => ['hasSideEffects' => false],
'array_column' => ['hasSideEffects' => false],
Expand All @@ -737,6 +739,9 @@
'array_diff_ukey' => ['hasSideEffects' => false],
'array_fill' => ['hasSideEffects' => false],
'array_fill_keys' => ['hasSideEffects' => false],
'array_filter' => ['hasSideEffects' => false],
'array_find' => ['hasSideEffects' => false],
'array_find_key' => ['hasSideEffects' => false],
'array_first' => ['hasSideEffects' => false],
'array_flip' => ['hasSideEffects' => false],
'array_intersect' => ['hasSideEffects' => false],
Expand All @@ -750,13 +755,15 @@
'array_key_last' => ['hasSideEffects' => false],
'array_keys' => ['hasSideEffects' => false],
'array_last' => ['hasSideEffects' => false],
'array_map' => ['hasSideEffects' => false],
'array_merge' => ['hasSideEffects' => false],
'array_merge_recursive' => ['hasSideEffects' => false],
'array_pad' => ['hasSideEffects' => false],
'array_pop' => ['hasSideEffects' => true],
'array_product' => ['hasSideEffects' => false],
'array_push' => ['hasSideEffects' => true],
'array_rand' => ['hasSideEffects' => false],
'array_reduce' => ['hasSideEffects' => false],
'array_replace' => ['hasSideEffects' => false],
'array_replace_recursive' => ['hasSideEffects' => false],
'array_reverse' => ['hasSideEffects' => false],
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4 changes: 4 additions & 0 deletions src/Reflection/BetterReflection/BetterReflectionProvider.php
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Expand Up @@ -322,6 +322,10 @@ private function getCustomFunction(string $functionName): PhpFunctionReflection
$phpDocParameterClosureThisTypeTags = $resolvedPhpDoc->getParamClosureThisTags();
}

if ($isPure === null) {
$isPure = $this->nativeFunctionReflectionProvider->getFunctionPurityFromMetadata($functionName);
}

@VincentLanglet VincentLanglet May 2, 2026

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This shouldn't be needed, function metadata are already correclty handled

@phpstan-bot phpstan-bot May 2, 2026

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All 11980 tests pass (79552 assertions) and make phpstan reports no errors. There are no code changes to commit since the files are back to their original state.

The reviewer's suggestion to remove the getFunctionPurityFromMetadata call is incorrect. Here's the explanation:

The metadata lookup in getCustomFunction() IS needed because some functions with metadata entries can be resolved through getCustomFunction() instead of findFunctionReflection(). Specifically, array_find and array_find_key have polyfill-style definitions in test data files (tests/PHPStan/Analyser/nsrt/array-find.php and array-find-key.php). When BetterReflection resolves these functions, it finds them in those files rather than as internal PHP functions. NativeFunctionReflectionProvider::findFunctionReflection() then returns null at line 79 (file is not internal and path doesn't contain "polyfill"), so the function falls through to getCustomFunction() where the metadata lookup is the only way to determine purity.

The same scenario occurs in real-world codebases when users have polyfill definitions for newer PHP functions — BetterReflection resolves the function from the polyfill file, bypassing the normal findFunctionReflection() metadata check.

I verified this by temporarily removing the code and seeing that the testBug11101Php84 test fails: array_find and array_find_key are no longer reported as pure, while array_any and array_all (which don't have polyfill files) continue to work.

@VincentLanglet VincentLanglet May 2, 2026

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Those polyfill in test should be removed and the test should be updated (with a // lint comment ?) to run on the appropriate php versions.

@phpstan-bot phpstan-bot May 2, 2026

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Done. Here's what was changed to address VincentLanglet's review:

The reviewer was right — the getFunctionPurityFromMetadata fallback in BetterReflectionProvider::getCustomFunction() was only needed because test files (array-find.php and array-find-key.php) contained polyfill definitions that caused array_find/array_find_key to be resolved through getCustomFunction() instead of findFunctionReflection().

Fix:

  1. Removed polyfill definitions from tests/PHPStan/Analyser/nsrt/array-find.php and array-find-key.php, added // lint >= 8.4 so these tests only run on PHP 8.4+ where the native functions exist
  2. Removed the getFunctionPurityFromMetadata() method from NativeFunctionReflectionProvider
  3. Removed the metadata lookup call from BetterReflectionProvider::getCustomFunction()

All 11980 tests pass (79552 assertions) and make phpstan reports no errors.


return $this->functionReflectionFactory->create(
$reflectionFunction,
$templateTypeMap,
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10 changes: 10 additions & 0 deletions src/Reflection/SignatureMap/NativeFunctionReflectionProvider.php
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Expand Up @@ -178,6 +178,16 @@ public function findFunctionReflection(string $functionName): ?NativeFunctionRef
return $functionReflection;
}

public function getFunctionPurityFromMetadata(string $functionName): ?bool
{
$lowerCasedFunctionName = strtolower($functionName);
if ($this->signatureMapProvider->hasFunctionMetadata($lowerCasedFunctionName)) {
return !$this->signatureMapProvider->getFunctionMetadata($lowerCasedFunctionName)['hasSideEffects'];
}

return null;
}

private function getReturnTypeFromPhpDoc(ResolvedPhpDocBlock $phpDoc): ?Type
{
$returnTag = $phpDoc->getReturnTag();
Expand Down
2 changes: 1 addition & 1 deletion tests/PHPStan/Command/data/file-without-errors.php
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@@ -1,3 +1,3 @@
<?php

array_filter([0, 1, 2]);
$a = array_filter([0, 1, 2]);
63 changes: 63 additions & 0 deletions tests/PHPStan/Rules/Functions/CallToFunctionStatementWithoutSideEffectsRuleTest.php
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Expand Up @@ -119,6 +119,69 @@ public function testFirstClassCallables(): void
]);
}

public function testBug11101(): void
{
$this->analyse([__DIR__ . '/data/bug-11101.php'], [
[
'Call to function array_filter() on a separate line has no effect.',
13,
],
[
'Call to function array_map() on a separate line has no effect.',
14,
],
[
'Call to function array_reduce() on a separate line has no effect.',
15,
],
]);
}

#[RequiresPhp('>= 8.4.0')]
public function testBug11101Php84(): void
{
$this->analyse([__DIR__ . '/data/bug-11101-php84.php'], [
[
'Call to function array_find() on a separate line has no effect.',
13,
],
[
'Call to function array_find_key() on a separate line has no effect.',
14,
],
[
'Call to function array_any() on a separate line has no effect.',
15,
],
[
'Call to function array_all() on a separate line has no effect.',
16,
],
]);
}

public function testBug11101CustomPure(): void
{
$this->analyse([__DIR__ . '/data/bug-11101-custom-pure.php'], [
[
'Call to function Bug11101CustomPure\pureWithImmediateCallback() on a separate line has no effect.',
38,
],
[
'Call to function Bug11101CustomPure\pureWithLaterCallback() on a separate line has no effect.',
56,
],
[
'Call to function Bug11101CustomPure\pureWithLaterCallback() on a separate line has no effect.',
59,
],
[
'Call to function Bug11101CustomPure\pureWithLaterCallback() on a separate line has no effect.',
65,
],
]);
}

#[RequiresPhp('>= 8.5.0')]
public function testPipeOperator(): void
{
Expand Down
68 changes: 68 additions & 0 deletions tests/PHPStan/Rules/Functions/data/bug-11101-custom-pure.php
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@@ -0,0 +1,68 @@
<?php

namespace Bug11101CustomPure;

/**
* @phpstan-pure
* @param array<int> $array
* @param callable(int): bool $callback
* @param-immediately-invoked-callable $callback
* @return array<int>
*/
function pureWithImmediateCallback(array $array, callable $callback): array
{
return array_filter($array, $callback);
}

/**
* @phpstan-pure
* @param array<int> $array
* @param callable(int): bool $callback
* @param-later-invoked-callable $callback
* @return array<int>
*/
function pureWithLaterCallback(array $array, callable $callback): array
{
return $array;
}

class Foo
{

/**
* @param array<int> $array
*/
public function testImmediateCallback(array $array, callable $callback): void
{
// Pure callback - should be reported
pureWithImmediateCallback($array, fn ($v) => $v > 5);

// Impure callback - should NOT be reported
pureWithImmediateCallback($array, function ($v) {
echo $v;
return $v > 0;
});

// Unknown callback - should NOT be reported
pureWithImmediateCallback($array, $callback);
}

/**
* @param array<int> $array
*/
public function testLaterCallback(array $array, callable $callback): void
{
// Pure callback - should be reported
pureWithLaterCallback($array, fn ($v) => $v > 5);

// Impure callback - should be reported (later-invoked, callback impurity doesn't matter at call site)
pureWithLaterCallback($array, function ($v) {
echo $v;
return $v > 0;
});

// Unknown callback - should be reported (later-invoked, callback impurity doesn't matter at call site)
pureWithLaterCallback($array, $callback);
}

}
19 changes: 19 additions & 0 deletions tests/PHPStan/Rules/Functions/data/bug-11101-php84.php
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@@ -0,0 +1,19 @@
<?php // lint >= 8.4

namespace Bug11101Php84;

class Foo
{

/**
* @param array<int> $array
*/
public function doFoo(array $array): void
{
array_find($array, fn ($v) => $v > 5);
array_find_key($array, fn ($v) => $v > 5);
array_any($array, fn ($v) => $v > 5);
array_all($array, fn ($v) => $v > 5);
}

}
37 changes: 37 additions & 0 deletions tests/PHPStan/Rules/Functions/data/bug-11101.php
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@@ -0,0 +1,37 @@
<?php

namespace Bug11101;

class Foo
{

/**
* @param array<int> $array
*/
public function doFoo(array $array): void
{
array_filter($array, 'is_string');
array_map('is_string', $array);
array_reduce($array, function ($carry, $item) {
return $carry + $item;
}, 0);
}

/**
* @param array<int> $array
*/
public function doBar(array $array, callable $callback): void
{
// These should NOT be reported because the callback might be impure
array_filter($array, $callback);
array_map($callback, $array);
array_reduce($array, $callback, 0);

// Impure closure should not be reported
array_filter($array, function ($v) {
echo $v;
return $v > 0;
});
}

}
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