fix(guzzle): distributed tracing header injection in HyperF/Swoole environments (#3544)

* fix(guzzle): inject distributed tracing headers before request execution

Use install_hook with pre-hook to inject headers into PSR-7 request
before it reaches any handler (curl or CoroutineHandler). This ensures
headers are propagated in HyperF/Swoole environments where CoroutineHandler
reads headers directly from the request object.

Fixes distributed tracing continuity for Guzzle in coroutine contexts.

* ALWAYS call overrideArguments() to prevent JIT compilation issues

Author: PROFeNoM

src/DDTrace/Integrations/Guzzle/GuzzleIntegration.php

@@ -2,6 +2,7 @@
 
 namespace DDTrace\Integrations\Guzzle;
 
+use DDTrace\HookData;
 use DDTrace\Http\Urls;
 use DDTrace\Integrations\HttpClientIntegrationHelper;
 use DDTrace\Integrations\Integration;
@@ -33,10 +34,65 @@ public static function handlePromiseResponse($response, SpanData $span)
 
     public static function init(): int
     {
-        /* Until we support both pre- and post- hooks on the same function, do
-         * not send distributed tracing headers; curl will almost guaranteed do
-         * it for us anyway. Just do a post-hook to get the response.
-         */
+        \DDTrace\install_hook(
+            'GuzzleHttp\Client::transfer',
+            static function (HookData $hook) {
+                // Note: We must ALWAYS call overrideArguments() to prevent JIT compilation issues.
+                // See ext/hook/uhook.c: "hooks wishing to override args must do so unconditionally"
+
+                $modified = false;
+
+                if (isset($hook->args[0])) {
+                    $request = $hook->args[0];
+
+                    if ($request instanceof \Psr\Http\Message\RequestInterface) {
+                        $dtHeaders = \DDTrace\generate_distributed_tracing_headers();
+
+                        if (!empty($dtHeaders)) {
+                            foreach ($dtHeaders as $name => $value) {
+                                if (!$request->hasHeader($name)) {
+                                    $request = $request->withHeader($name, $value);
+                                    $modified = true;
+                                }
+                            }
+
+                            if ($modified) {
+                                $hook->args[0] = $request;
+                            }
+                        }
+                    }
+                }
+
+                // CRITICAL: Always call overrideArguments to prevent JIT from breaking header injection
+                $hook->overrideArguments($hook->args);
+            },
+            static function (HookData $hook) {
+                $span = $hook->span();
+                if (!$span) {
+                    return;
+                }
+
+                $span->resource = 'transfer';
+                $span->name = 'GuzzleHttp\Client.transfer';
+                Integration::handleInternalSpanServiceName($span, self::NAME);
+                $span->type = Type::HTTP_CLIENT;
+                $span->meta[Tag::SPAN_KIND] = Tag::SPAN_KIND_VALUE_CLIENT;
+                $span->meta[Tag::COMPONENT] = self::NAME;
+                $span->peerServiceSources = HttpClientIntegrationHelper::PEER_SERVICE_SOURCES;
+
+                if (isset($hook->args[0])) {
+                    self::addRequestInfo($span, $hook->args[0]);
+                }
+
+                if (isset($hook->returned)) {
+                    $response = $hook->returned;
+                    if (\is_a($response, 'GuzzleHttp\Promise\PromiseInterface')) {
+                        self::handlePromiseResponse($response, $span);
+                    }
+                }
+            }
+        );
+
         \DDTrace\trace_method(
             'GuzzleHttp\Client',
             'send',
@@ -52,8 +108,6 @@ static function (SpanData $span, $args, $retval) {
                     \defined('GuzzleHttp\ClientInterface::VERSION')
                     && substr(\GuzzleHttp\ClientInterface::VERSION, 0, 2) === '5.'
                 ) {
-                    // On Guzzle 6+, we do not need to generate peer.service for the send span,
-                    // as the terminal span is 'transfer'
                     $span->peerServiceSources = HttpClientIntegrationHelper::PEER_SERVICE_SOURCES;
                 }
 
@@ -80,30 +134,6 @@ static function (SpanData $span, $args, $retval) {
             }
         );
 
-        \DDTrace\trace_method(
-            'GuzzleHttp\Client',
-            'transfer',
-            static function (SpanData $span, $args, $retval) {
-                $span->resource = 'transfer';
-                $span->name = 'GuzzleHttp\Client.transfer';
-                Integration::handleInternalSpanServiceName($span, self::NAME);
-                $span->type = Type::HTTP_CLIENT;
-                $span->meta[Tag::SPAN_KIND] = Tag::SPAN_KIND_VALUE_CLIENT;
-                $span->meta[Tag::COMPONENT] = self::NAME;
-                $span->peerServiceSources = HttpClientIntegrationHelper::PEER_SERVICE_SOURCES;
-
-                if (isset($args[0])) {
-                    self::addRequestInfo($span, $args[0]);
-                }
-                if (isset($retval)) {
-                    $response = $retval;
-                    if (\is_a($response, 'GuzzleHttp\Promise\PromiseInterface')) {
-                        self::handlePromiseResponse($response, $span);
-                    }
-                }
-            }
-        );
-
         return Integration::LOADED;
     }