Invalid FieldMask error while fetching batched gmail get responses

[mohsin]

I'm trying to make batched requests more efficient by getting partial responses. I'm interested to get just certain headers (from, to, subject) and the message body.

My code works fine when I run it like this:

$client = getClient();
$client->setUseBatch(true);
$service = new Google_Service_Gmail($client);

$batch = new Google_Http_Batch($client, false, null, 'batch/gmail/v1');
$request1 = $service->users_messages->get('me', '17eb57d85dd4933d', ['format'=>'full', 'fields' => 'id,snippet,payload(headers(name,value),body,parts)']);
$request2 = $service->users_messages->get('me', '17eb4fe58a1b3be6', ['format'=>'full', 'fields' => 'id,snippet,payload(headers(name,value),body,parts)']);
$batch->add($request1, "message" . '-17eb57d85dd4933d');
$batch->add($request2, "message" . '-17eb4fe58a1b3be6');
$result = $batch->execute();
var_dump($result);

As you can see in the above request, I'm getting ALL the header name, value pairs as payload(headers(name,value). But when I change the code to select only certain headers (I'm interested only in From, To, Subject).

$request1 = $service->users_messages->get('me', '17eb57d85dd4933d', ['format'=>'full', 'fields' => 'id,snippet,payload(headers(name,value)[name=From,To,Subject],body,parts)']);

The API throws me an error:

Invalid FieldMask 'id,snippet,payload(headers(name,value)[name=From,To,Subject],body,parts)'. Map keys should be represented as ["some_key"].

I tried changing it to headers(name,value)[name="From",name="To",name="Subject"] and a few other formats but cannot figure out how to get it right. The API documentation too doesn't go in-depth to discuss how to select specific headers in key-value pairs so some help would be appreciated. Thanks.

[LindaLawton]

As far as i know you cant map on keys like that use this I have never heard of it and cant really find anything in the docs about it. Would be awesome if it did work though.

This works:

   id,snippet,payload(headers,body,parts)

you should use the Try me on this page if you want to test it out though.