From 1c02184e2c96c926222ad4f6c3119c102017677d Mon Sep 17 00:00:00 2001
From: Fernando Briano <fernando@picandocodigo.net>
Date: Fri, 12 Jun 2026 15:32:00 +0100
Subject: [PATCH] Fixes NoMethodError when Content-Type lacks compatible-with
 parameter

Fixes #2973
---
 .../lib/elasticsearch/api/utils.rb            |  2 +-
 .../spec/unit/ndjson_endpoints/bulk_spec.rb   | 60 ++++++++++++++-----
 2 files changed, 45 insertions(+), 17 deletions(-)

diff --git a/elasticsearch-api/lib/elasticsearch/api/utils.rb b/elasticsearch-api/lib/elasticsearch/api/utils.rb
index 65591d403..1f34f7bc6 100644
--- a/elasticsearch-api/lib/elasticsearch/api/utils.rb
+++ b/elasticsearch-api/lib/elasticsearch/api/utils.rb
@@ -178,7 +178,7 @@ def rescue_from_not_found(&block)
       def update_ndjson_headers!(headers, client_headers)
         current_content = client_headers.keys.find { |c| c.match?(/content-?_?type/i) } || 'content-type'
         current_accept = client_headers.keys.find { |c| c.match?(/accept/i) } || 'accept'
-        version = client_headers[current_content].match(/compatible-with=([0-9]+)/)[1] || 9
+        version = client_headers[current_content].match(/compatible-with=([0-9]+)/)&.[](1) || 9
 
         headers.merge!(
           {
diff --git a/elasticsearch-api/spec/unit/ndjson_endpoints/bulk_spec.rb b/elasticsearch-api/spec/unit/ndjson_endpoints/bulk_spec.rb
index d775c4e12..12a7064d1 100644
--- a/elasticsearch-api/spec/unit/ndjson_endpoints/bulk_spec.rb
+++ b/elasticsearch-api/spec/unit/ndjson_endpoints/bulk_spec.rb
@@ -33,14 +33,14 @@
     it 'does not override headers' do
       allow(client)
         .to receive(:perform_request)
-              .with(
-                Elasticsearch::API::HTTP_POST,
-                '_bulk',
-                {},
-                {},
-                expected_headers,
-                { endpoint: 'bulk' }
-              )
+        .with(
+          Elasticsearch::API::HTTP_POST,
+          '_bulk',
+          {},
+          {},
+          expected_headers,
+          { endpoint: 'bulk' }
+        )
       expect(client.bulk(body: {})).to be_a Elasticsearch::API::Response
     end
   end
@@ -110,15 +110,43 @@
     it 'does not override version in headers' do
       allow(client)
         .to receive(:perform_request)
-              .with(
-                Elasticsearch::API::HTTP_POST,
-                '_bulk',
-                {},
-                {},
-                expected_headers,
-                { endpoint: 'bulk' }
-              )
+        .with(
+          Elasticsearch::API::HTTP_POST,
+          '_bulk',
+          {},
+          {},
+          expected_headers,
+          { endpoint: 'bulk' }
+        )
       expect(client.bulk(body: {}, headers: { x_custom: 'Custom header' })).to be_a Elasticsearch::API::Response
     end
   end
+
+  context 'when using application/x-ndjson as a content-type header' do
+    let(:client) do
+      Elasticsearch::Client.new(
+        url: 'http://localhost:9200',
+        transport_options: {
+          headers: { 'Content-Type' => 'application/x-ndjson' }
+        }
+      )
+    end
+
+    it 'doesnt error when using bulk' do
+      allow(client)
+        .to receive(:perform_request)
+        .with(
+          Elasticsearch::API::HTTP_POST,
+          '_bulk',
+          {},
+          {},
+          {
+            'Content-Type' => 'application/vnd.elasticsearch+x-ndjson; compatible-with=9',
+            'accept' => 'application/vnd.elasticsearch+x-ndjson; compatible-with=9'
+          },
+          { endpoint: 'bulk' }
+        )
+      expect(client.bulk(body: {})).to be_a Elasticsearch::API::Response
+    end
+  end
 end