JSON parsing fails when gRPC PHP Extension is enabled and REST transport is used

[PierrickVoulet]

When C implementation of grpc is enabled in php.ini and rest transport is enabled from code ->withTransport('rest') the ConversionUploadServiceGapicClient.uploadClickConversions method fails:

#0 /home/vagrant/google-oct/app/Vendor/google/gax/src/Transport/RestTransport.php(125): Google\Protobuf\Internal\Message->mergeFromJsonString()
#1 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(204): Google\ApiCore\Transport\RestTransport->Google\ApiCore\Transport\{closure}()
#2 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(153): GuzzleHttp\Promise\Promise::callHandler()
#3 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/TaskQueue.php(48): GuzzleHttp\Promise\Promise::GuzzleHttp\Promise\{closure}()
#4 /home/vagrant/google-oct/app/Vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(118): GuzzleHttp\Promise\TaskQueue->run()
#5 /home/vagrant/google-oct/app/Vendor/guzzlehttp/guzzle/src/Handler/CurlMultiHandler.php(145): GuzzleHttp\Handler\CurlMultiHandler->tick()
#6 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(248): GuzzleHttp\Handler\CurlMultiHandler->execute()
#7 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(224): GuzzleHttp\Promise\Promise->invokeWaitFn()
#8 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(269): GuzzleHttp\Promise\Promise->waitIfPending()
#9 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(226): GuzzleHttp\Promise\Promise->invokeWaitList()
#10 /home/vagrant/google-oct/app/Vendor/guzzlehttp/promises/src/Promise.php(62): GuzzleHttp\Promise\Promise->waitIfPending()
#11 /home/vagrant/google-oct/app/Vendor/googleads/google-ads-php/src/Google/Ads/GoogleAds/V8/Services/Gapic/ConversionUploadServiceGapicClient.php(302): GuzzleHttp\Promise\Promise->wait()
#12 /home/vagrant/google-oct/app/Controller/Component/GoogleAdsApiComponent.php(383): Google\Ads\GoogleAds\V8\Services\Gapic\ConversionUploadServiceGapicClient->uploadClickConversions()
#13 /home/vagrant/google-oct/app/Controller/Component/GoogleAdsApiComponent.php(129): GoogleAdsApiComponent->uploadOfflineConversion()
#14 /home/vagrant/google-oct/app/Controller/ServicesController.php(8544): GoogleAdsApiComponent->handleOfflineConversion()
#15 [internal function]: ServicesController->testGoogleAdsLib()
#16 /home/vagrant/google-oct/lib/Cake/Controller/Controller.php(499): ReflectionMethod->invokeArgs()
#17 /home/vagrant/google-oct/lib/Cake/Routing/Dispatcher.php(193): Controller->invokeAction()
#18 /home/vagrant/google-oct/lib/Cake/Routing/Dispatcher.php(167): Dispatcher->_invoke()
#19 /home/vagrant/google-oct/app/webroot/index.php(110): Dispatcher->dispatch()
#20 {main}

Error: Error occurred during parsing: Error parsing JSON @7:87: Type was not found

Originally posted by @rpmgr in #640 (comment)

[PierrickVoulet]

A few other things to note:

• A workaround is to disable the grpc PHP extension.
• This does not seem to happen when using GoogleAdsServiceGapicClient.search.
• This has a fairly low impact because the rest transport is typically used when grpc is unavailable (i.e. the gRPC PHP extension cannot be installed and enabled on the environment).