Add support for Elasticsearch api versioning header

Originally added in Elasticsearch in commit
2c5f1d1569, removed in OpenSearch in
3eac282c57

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

Signed-off-by: Rushi Agrawal <[email protected]>

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())
 

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:

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"{}"):