From ea397e0f92806de9f27e5354691cb4b0d41893a8 Mon Sep 17 00:00:00 2001
From: Rushi Agrawal <rushi.agr@gmail.com>
Date: Thu, 26 Aug 2021 18:55:25 +0530
Subject: [PATCH] Add support for Elasticsearch api versioning header

Originally added in Elasticsearch in commit
2c5f1d15697e75f932a2c82634927e22931d4879, removed in OpenSearch in
3eac282c57552ef196e16c35132cca1d06f122b2

Note that this just adds support of 'elasticsearch' header, there's no
'opensearch' header support as such.

Signed-off-by: Rushi Agrawal <rushi.agr@gmail.com>
---
 opensearch/connection/base.py      |  6 ++++++
 opensearch/serializer.py           |  5 +++++
 test_opensearch/test_connection.py | 21 +++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/opensearch/connection/base.py b/opensearch/connection/base.py
index 05d81c71..b8c27237 100644
--- a/opensearch/connection/base.py
+++ b/opensearch/connection/base.py
@@ -28,6 +28,7 @@ import binascii
 import gzip
 import io
 import logging
+import os
 import re
 import warnings
 from platform import python_version
@@ -127,6 +128,11 @@ class Connection(object):
         if opaque_id:
             self.headers["x-opaque-id"] = opaque_id
 
+        if os.getenv("ELASTIC_CLIENT_APIVERSIONING") == "1":
+            self.headers.setdefault(
+                "accept", "application/vnd.elasticsearch+json;compatible-with=7"
+            )
+
         self.headers.setdefault("content-type", "application/json")
         self.headers.setdefault("user-agent", self._get_default_user_agent())
 
diff --git a/opensearch/serializer.py b/opensearch/serializer.py
index fcc9b146..d7180e8e 100644
--- a/opensearch/serializer.py
+++ b/opensearch/serializer.py
@@ -163,6 +163,11 @@ class Deserializer(object):
         if not mimetype:
             deserializer = self.default
         else:
+            # Treat 'application/vnd.elasticsearch+json'
+            # as application/json for compatibility.
+            if mimetype == "application/vnd.elasticsearch+json":
+                mimetype = "application/json"
+
             # split out charset
             mimetype, _, _ = mimetype.partition(";")
             try:
diff --git a/test_opensearch/test_connection.py b/test_opensearch/test_connection.py
index c02a7183..e296a29b 100644
--- a/test_opensearch/test_connection.py
+++ b/test_opensearch/test_connection.py
@@ -28,6 +28,7 @@
 import gzip
 import io
 import json
+import os
 import re
 import ssl
 import warnings
@@ -173,6 +174,26 @@ class TestBaseConnection(TestCase):
             conn = Connection(**kwargs)
             assert conn.host == expected_host
 
+    def test_compatibility_accept_header(self):
+        try:
+            conn = Connection()
+            assert "accept" not in conn.headers
+
+            os.environ["ELASTIC_CLIENT_APIVERSIONING"] = "0"
+
+            conn = Connection()
+            assert "accept" not in conn.headers
+
+            os.environ["ELASTIC_CLIENT_APIVERSIONING"] = "1"
+
+            conn = Connection()
+            assert (
+                conn.headers["accept"]
+                == "application/vnd.elasticsearch+json;compatible-with=7"
+            )
+        finally:
+            os.environ.pop("ELASTIC_CLIENT_APIVERSIONING")
+
 
 class TestUrllib3Connection(TestCase):
     def _get_mock_connection(self, connection_params={}, response_body=b"{}"):