implement getAll function in TextMap Extract (#1570)

* implement getAll function in TextMap Extract

* refactor propagation interfaces to introduce ExtendedPropagationGetterInterface

* Refactor getAll method in SanitizeCombinedHeadersPropagationGetter to streamline conditional logic for getter instance check

Author: ycchuang99

Propagation/ArrayAccessGetterSetter.php

@@ -16,10 +16,10 @@
 /**
  * @see https://github.com/open-telemetry/opentelemetry-specification/blob/v1.6.1/specification/context/api-propagators.md#textmap-propagator Getter and Setter.
  *
- * Default implementation of {@see PropagationGetterInterface} and {@see PropagationSetterInterface}.
+ * Default implementation of {@see ExtendedPropagationGetterInterface} and {@see PropagationSetterInterface}.
  * This type is used if no custom getter/setter is provided to {@see TextMapPropagatorInterface::inject()} or {@see TextMapPropagatorInterface::extract()}.
  */
-final class ArrayAccessGetterSetter implements PropagationGetterInterface, PropagationSetterInterface
+final class ArrayAccessGetterSetter implements ExtendedPropagationGetterInterface, PropagationSetterInterface
 {
     private static ?self $instance = null;
 
@@ -78,6 +78,29 @@ public function get($carrier, string $key): ?string
         );
     }
 
+    /** {@inheritdoc} */
+    public function getAll($carrier, string $key): array
+    {
+        if ($this->isSupportedCarrier($carrier)) {
+            $value = $carrier[$this->resolveKey($carrier, $key)] ?? null;
+            if (is_array($value) && $value) {
+                return array_values(array_filter($value, 'is_string'));
+            }
+
+            return is_string($value)
+                ? [$value]
+                : [];
+        }
+
+        throw new InvalidArgumentException(
+            sprintf(
+                'Unsupported carrier type: %s. Unable to get value associated with key:%s',
+                get_debug_type($carrier),
+                $key
+            )
+        );
+    }
+
     /** {@inheritdoc} */
     public function set(&$carrier, string $key, string $value): void
     {

Propagation/ExtendedPropagationGetterInterface.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OpenTelemetry\Context\Propagation;
+
+/**
+ * Interface for getting values from a carrier.
+ * This interface extends the base PropagationGetterInterface to avoid breaking changes.
+ */
+interface ExtendedPropagationGetterInterface extends PropagationGetterInterface
+{
+    /**
+     * Gets all values of a given key from a carrier.
+     *
+     * @see https://github.com/open-telemetry/opentelemetry-specification/blob/v1.44.0/specification/context/api-propagators.md#getall
+     *
+     * @return list<string>
+     */
+    public function getAll($carrier, string $key): array;
+}

Propagation/SanitizeCombinedHeadersPropagationGetter.php

@@ -12,7 +12,7 @@
  * handle edge cases where the header has a trailing ';' or an empty trace state.
  * We also need to trim trailing separators from the header, found when a header is empty.
  */
-final class SanitizeCombinedHeadersPropagationGetter implements PropagationGetterInterface
+final class SanitizeCombinedHeadersPropagationGetter implements ExtendedPropagationGetterInterface
 {
     private const LIST_MEMBERS_SEPARATOR = ',';
     private const SERVER_CONCAT_HEADERS_REGEX = '/;(?=[^,=;]*=|$)/';
@@ -40,4 +40,23 @@ public function get($carrier, string $key): ?string
             $value,
         );
     }
+
+    public function getAll($carrier, string $key): array
+    {
+        $value = $this->getter instanceof ExtendedPropagationGetterInterface
+            ? $this->getter->getAll($carrier, $key)
+            : (array) $this->getter->get($carrier, $key);
+
+        if ($value === []) {
+            return [];
+        }
+
+        $value = preg_replace(
+            [self::SERVER_CONCAT_HEADERS_REGEX, self::TRAILING_LEADING_SEPARATOR_REGEX],
+            [self::LIST_MEMBERS_SEPARATOR],
+            $value,
+        );
+
+        return array_values($value);
+    }
 }