Gmail API removes message part - ruby

Question

When I send a message with attachment using the Gmail API, the recipient receives the message without the attachment.
What is strange though is that:
1: in the sent folder of the sender, I do see the attachment properly
2: if I send to myself, both message are fine (in sent folder and in inbox folder)
3: if I use with GMail SMTP with the same raw message, it works fine
4: if I use a 3rd party SMTP with the same raw message, it works fine.
Point number 1+2 super puzzling.
Here is the source of the original message in the sent folder:
Received: from 13936824666 named unknown by gmailapi.google.com with HTTPREST; Wed, 25 Jan 2017 18:44:30 -0500
Date: Wed, 25 Jan 2017 18:44:30 -0500
From: Jeremy Chatelaine <source#gmail.com>
To: Jeremy <target#domain.com>
Message-Id: <CABX8Avad0vTtu8=jotRD5HM1r0My-ZKeV7RFRo0TmTxf5PNd0g#mail.gmail.com>
Subject: Export
Mime-Version: 1.0
Content-Type: multipart/alternative; boundary="--==_mimepart_5889385be5066_a133fd0f785e20837629"; charset=UTF-8
Content-Transfer-Encoding: 7bit
----==_mimepart_5889385be5066_a133fd0f785e20837629
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Please find attached the message
----==_mimepart_5889385be5066_a133fd0f785e20837629
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit
Please find attached the message
----==_mimepart_5889385be5066_a133fd0f785e20837629
Content-Type: text/csv; charset=UTF-8; filename=export.csv
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename=export.csv
Content-ID: <5889385be6fd7_a133fd0f785e20837735#jeremy.mail>
Some text...
----==_mimepart_5889385be5066_a133fd0f785e20837629--
Here is the source of the original message in the recipient inbox folder:
Delivered-To: target#domain.com
Received: by 10.55.110.193 with SMTP id j184csp1999707qkc;
Wed, 25 Jan 2017 16:30:42 -0800 (PST)
X-Received: by 10.107.34.213 with SMTP id i204mr540101ioi.203.1485390642385;
Wed, 25 Jan 2017 16:30:42 -0800 (PST)
Return-Path: <source#domain.com>
Received: from mail-it0-x22b.google.com (mail-it0-x22b.google.com. [2607:f8b0:4001:c0b::22b])
by mx.google.com with ESMTPS id 88si336719ioq.54.2017.01.25.16.30.42
for <target#domain.com>
(version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128);
Wed, 25 Jan 2017 16:30:42 -0800 (PST)
Received-SPF: pass (google.com: domain of source#domain.com designates 2607:f8b0:4001:c0b::22b as permitted sender) client-ip=2607:f8b0:4001:c0b::22b;
Authentication-Results: mx.google.com;
dkim=pass header.i=#domain.com;
spf=pass (google.com: domain of source#domain.com designates 2607:f8b0:4001:c0b::22b as permitted sender) smtp.mailfrom=source#domain.com
Received: by mail-it0-x22b.google.com with SMTP id 203so119411500ith.0
for <target#domain.com>; Wed, 25 Jan 2017 16:30:42 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=domain.com; s=domain;
h=from:mime-version:date:message-id:subject:to;
bh=wx26/V0bJk9VItDp3TAvKl28UAn7IRQq4NITJZDM+Co=;
b=L3KTzPTCoIJUfAacuJy+PE8jHnY9iwGuXUWSpZzneRs5bvMysigSMyPGn1YicyIvQ6
d/LvbEJPlsu+S0zElhIVPITjAmXKDKNIKwLQDHpkcKnnI3btBUrENN923fMtS1fDdHyV
3At0QenKrb34uQqYYoHtX2WU4nyYrISbYKL62=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=1e100.net; s=20161025;
h=x-gm-message-state:from:mime-version:date:message-id:subject:to;
bh=wx26/V0bJk9VItDp3TAvKl28UAn7IRQq4NITJZDM+Co=;
b=tGPSHjI3iRzjrI0jGHVX76uTw7OXYC4B2bP0qQKgQotBWru+Pn5Ci9A1Qop9oGN1Ys
fnxCgLOLG8ZJU165ODBNX1DGjPa8ud9SWg18FTsxIjNw9qTr1yJqbWr0LToJi7HdQUr8
7Aaiqil7PbPUf5SdxLCqwBNf660Rn9Sd/ADZeT1Bc2+iYQcizjiK/rOPPX+X1ZndvqxP
Ok3Ac2yyIWxi+m4xaPEztcF4JXFZDlJWFdclUDv4s5Jdc0eb1HmB5d2r1qroGLo5MTjd
d7jO1nRsKTO5I9I69p9AgC+LpDiWBxgzZMBVsU6vVpeZ03/pCroyk9DHDUAjn3ijtlFh
O2vw==
X-Gm-Message-State: AIkVDXJo2tPJlkHkthgEjnxYp7vz5Rfpn91pWCS7zEurkSiDhJtyzLpUoSDORq37K/7ATCRSyLAypKIYrdYwEiL2
X-Received: by 10.36.84.148 with SMTP id t142mr20263701ita.90.1485390641934; Wed, 25 Jan 2017 16:30:41 -0800 (PST)
Received: from 13936824667 named unknown by gmailapi.google.com with HTTPREST; Wed, 25 Jan 2017 19:30:41 -0500
From: Jeremy Chatelaine <source#domain.com>
Mime-Version: 1.0
Date: Wed, 25 Jan 2017 19:30:41 -0500
Message-ID: <CABK5xHonVstaJHWHfvBJFF1BK5Y0B8NJsAJTPFokPNAUcawhGA#mail.gmail.com>
Subject: Export
To: Jeremy <target#domain.com>
Content-Type: multipart/alternative; boundary=001a1143a6cc90c9040546f4753f
--001a1143a6cc90c9040546f4753f
Content-Type: text/plain; charset=UTF-8
Please find attached your requested export
--001a1143a6cc90c9040546f4753f
Content-Type: text/html; charset=UTF-8
Please find attached your requested export
--001a1143a6cc90c9040546f4753f--
As you can see, the mime part where I had my text attachment vanished.
Here is how the message is produced (cut for clarity)
msg = Mail.new
html_part = Mail::Part.new do
content_type 'text/html; charset=UTF-8'
body html_body
end
msg.html_part = html_part
new_text = plan_text
text_part = Mail::Part.new do
body new_text
end
msg.text_part = text_part
file_paths.each do |file_path|
msg.add_file(file_path)
# I also tried like that, same result
#open(file_path) do |file|
# msg.attachments[file_path] = file.read
#end
end
raw_message = msg.to_s
Here is how I send with the gmail api
client = Google::APIClient.new(:application_name => "app", :application_version => "1")
client.authorization.client_id = "someverylongnumbers.apps.googleusercontent.com"
client.authorization.client_secret = "morerandomletters"
client.authorization.access_token = token
client.authorization.scope = [
"https://www.googleapis.com/auth/gmail.modify"
]
gmail_api = client.discovered_api('gmail', 'v1') # https://www.googleapis.com/auth/gmail.modify
result = client.execute(
:api_method => gmail_api.users.messages.to_h['gmail.users.messages.send'],
:parameters => {
'userId' => "me"
},
:body_object => {
'raw' => Base64.urlsafe_encode64(raw_message)
}
)
What is wrong with this?