Fix exponential time complexity in AliasArguments with circular type references

[artem-schander]

Problem

AliasArguments::getAliasesInFields() has exponential time complexity when processing input types with circular references, causing severe performance degradation in mutations.

Root Cause: The method traverses ALL possible fields in the type schema, not just fields present in the request data. With circular type references (e.g., PageInput ↔ SectionInput) and a depth limit calculated from request data, this creates exponential traversal.

Evidence

Real-world example:

• Before fix: Mutation taking 11+ seconds
• After fix: Same mutation taking ~150ms
• Improvement: 98.7% reduction in execution time

Debug logging revealed:

• 6 million recursive calls before timeout
• Depth reaching 12-13 levels with circular paths like: newsletter.page.reference.page.redirect.page.translationOrigin.translationOrigin.translations.*.redirect.page...

Solution

Only traverse fields that exist in the actual request data. This prevents exponential explosion while preserving full alias functionality.

Changes

Modified signature:

protected function getAliasesInFields(array $fields, ?array $requestData = null, string $prefix = ''): array

Key addition:

// Skip fields not present in actual request data
if ($requestData !== null && !array_key_exists($name, $requestData)) {
    continue;
}

Recursive calls now pass data:

$pathAndAlias = $pathAndAlias + $this->getAliasesInFields(
    $type->getFields(),
    $fieldData,  // Pass actual data instead of all possible fields
    $newPrefix
);

Testing

• ✅ Tested with deeply nested input types (11 levels)
• ✅ Tested with circular type references (PageInput ↔ SectionInput)
• ✅ Verified alias functionality preserved (deprecated field name mapping)
• ✅ Verified legitimate nested types work (e.g., Page->translations array)
• ✅ 124 production mutations tested successfully

Impact

This fix affects any application with:

• Circular type references in input types (common in CMS/e-commerce)
• Deeply nested input data
• Alias usage for backward compatibility

Backward Compatibility

✅ Fully backward compatible - the fix only changes the traversal strategy, not the API or functionality.