Slightly reduce RAM usage (#7301)

* No need to re-require sidekiq plugins, they are required via Gemfile

* Add derailed_benchmarks tool, no need to require TTY gems in Gemfile

* Replace ruby-oembed with FetchOEmbedService

Reduce startup by 45382 allocated objects

* Remove preloaded JSON-LD in favour of caching HTTP responses

Reduce boot RAM by about 6 MiB

* Fix tests

* Fix test suite by stubbing out JSON-LD contexts

1 files changed, 125 insertions, 0 deletions

diff --git a/spec/services/fetch_oembed_service_spec.rb b/spec/services/fetch_oembed_service_spec.rb
new file mode 100644
index 000000000..706eb3f2a
--- /dev/null
+++ b/spec/services/fetch_oembed_service_spec.rb
@@ -0,0 +1,125 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe FetchOEmbedService, type: :service do
+  subject { described_class.new }
+
+  before do
+    stub_request(:get, "https://host.test/provider.json").to_return(status: 404)
+    stub_request(:get, "https://host.test/provider.xml").to_return(status: 404)
+  end
+
+  describe 'discover_provider' do
+    context 'when status code is 200 and MIME type is text/html' do
+      context 'Both of JSON and XML provider are discoverable' do
+        before do
+          stub_request(:get, 'https://host.test/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_json_xml.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for JSON provider if :format option is set to :json' do
+          subject.call('https://host.test/oembed.html', format: :json)
+          expect(subject.endpoint_url).to eq 'https://host.test/provider.json'
+          expect(subject.format).to eq :json
+        end
+
+        it 'returns new OEmbed::Provider for XML provider if :format option is set to :xml' do
+          subject.call('https://host.test/oembed.html', format: :xml)
+          expect(subject.endpoint_url).to eq 'https://host.test/provider.xml'
+          expect(subject.format).to eq :xml
+        end
+      end
+
+      context 'JSON provider is discoverable while XML provider is not' do
+        before do
+          stub_request(:get, 'https://host.test/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_json.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for JSON provider' do
+          subject.call('https://host.test/oembed.html')
+          expect(subject.endpoint_url).to eq 'https://host.test/provider.json'
+          expect(subject.format).to eq :json
+        end
+      end
+
+      context 'XML provider is discoverable while JSON provider is not' do
+        before do
+          stub_request(:get, 'https://host.test/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_xml.html')
+          )
+        end
+
+        it 'returns new OEmbed::Provider for XML provider' do
+          subject.call('https://host.test/oembed.html')
+          expect(subject.endpoint_url).to eq 'https://host.test/provider.xml'
+          expect(subject.format).to eq :xml
+        end
+      end
+
+      context 'Invalid XML provider is discoverable while JSON provider is not' do
+        before do
+          stub_request(:get, 'https://host.test/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_invalid_xml.html')
+          )
+        end
+
+        it 'returns nil' do
+          expect(subject.call('https://host.test/oembed.html')).to be_nil
+        end
+      end
+
+      context 'Neither of JSON and XML provider is discoverable' do
+        before do
+          stub_request(:get, 'https://host.test/oembed.html').to_return(
+            status: 200,
+            headers: { 'Content-Type': 'text/html' },
+            body: request_fixture('oembed_undiscoverable.html')
+          )
+        end
+
+        it 'returns nil' do
+          expect(subject.call('https://host.test/oembed.html')).to be_nil
+        end
+      end
+    end
+
+    context 'when status code is not 200' do
+      before do
+        stub_request(:get, 'https://host.test/oembed.html').to_return(
+          status: 400,
+          headers: { 'Content-Type': 'text/html' },
+          body: request_fixture('oembed_xml.html')
+        )
+      end
+
+      it 'returns nil' do
+        expect(subject.call('https://host.test/oembed.html')).to be_nil
+      end
+    end
+
+    context 'when MIME type is not text/html' do
+      before do
+        stub_request(:get, 'https://host.test/oembed.html').to_return(
+          status: 200,
+          body: request_fixture('oembed_xml.html')
+        )
+      end
+
+      it 'returns nil' do
+        expect(subject.call('https://host.test/oembed.html')).to be_nil
+      end
+    end
+  end
+end