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<?php
declare(strict_types=1);
namespace Shirabe\PluginClassifier;
/**
* Per-method pure/mutator decision (see "pure/mutator" in
* docs/dev/plugin-class-classification.md): a method is a mutator iff it
* writes $this directly, passes a $this-rooted expression into a by-ref
* parameter, contains a statically unresolvable call that a $this-rooted
* expression escapes into, or (transitively) calls a mutator method on the
* same object.
*/
final class PurityAnalyzer
{
/** @var array<string, string> "Fqcn::lowername" => 'pure' | 'mutator' | 'n/a' */
public array $verdicts = [];
public function __construct(private readonly SourceParser $sources)
{
}
public function run(): void
{
// Seed with local evidence.
foreach ($this->sources->classes as $fqcn => $info) {
foreach ($info->methods as $lname => $method) {
$key = "$fqcn::$lname";
if ($method->static || $method->abstract) {
$this->verdicts[$key] = 'n/a';
continue;
}
$this->verdicts[$key] = $this->locallyMutates($fqcn, $method) ? 'mutator' : 'pure';
}
}
// Propagate through same-object calls until stable.
do {
$changed = false;
foreach ($this->sources->classes as $fqcn => $info) {
foreach ($info->methods as $lname => $method) {
$key = "$fqcn::$lname";
if ($this->verdicts[$key] !== 'pure') {
continue;
}
foreach ($method->selfCalls as $call) {
$callee = $this->resolveMethod($fqcn, $call['name']);
if ($callee === null) {
// Magic __call or a method we cannot see.
$this->verdicts[$key] = 'mutator';
$changed = true;
break;
}
[$calleeClass, $calleeMethod] = $callee;
$calleeVerdict = $this->verdicts["$calleeClass::" . strtolower($calleeMethod->name)] ?? 'mutator';
if ($calleeVerdict === 'mutator') {
$this->verdicts[$key] = 'mutator';
$changed = true;
break;
}
if (array_intersect($call['thisArgs'], $calleeMethod->byRefParamPositions()) !== []) {
$this->verdicts[$key] = 'mutator';
$changed = true;
break;
}
}
}
}
} while ($changed);
}
private function locallyMutates(string $fqcn, MethodInfo $method): bool
{
if ($method->mutatesThisDirectly || $method->thisEscapesUnresolved) {
return true;
}
foreach ($method->externalCalls as $call) {
$positions = $this->byRefPositionsOf($call['class'], $call['method']);
if ($positions === null) {
// Callee signature unknown: conservative.
return true;
}
if (array_intersect($call['thisArgs'], $positions) !== []) {
return true;
}
}
return false;
}
/** @return list<int>|null null when the signature cannot be resolved */
private function byRefPositionsOf(string $class, string $lowerMethod): ?array
{
$resolved = $this->resolveMethod($class, $lowerMethod);
if ($resolved !== null) {
return $resolved[1]->byRefParamPositions();
}
$vendor = VendorPackages::BY_REF[$class] ?? null;
if ($vendor !== null) {
return $vendor[$lowerMethod] ?? [];
}
if (VendorPackages::lookup($class) !== null) {
// Vendor packages other than the ones tabled expose no by-ref
// parameters in APIs composer calls.
return [];
}
return null;
}
/** @return array{string, MethodInfo}|null resolved (declaring class, method) */
private function resolveMethod(string $class, string $lowerMethod): ?array
{
$seen = [];
$current = $class;
while ($current !== null && !isset($seen[$current])) {
$seen[$current] = true;
$info = $this->sources->classes[$current] ?? null;
if ($info === null) {
return null;
}
if (isset($info->methods[$lowerMethod])) {
return [$current, $info->methods[$lowerMethod]];
}
$current = $info->parent;
}
return null;
}
}
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