reimplement const-lookup from Faraday::RackBuilder::Handler

lib/faraday/adapter_registry.rb

@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+require 'monitor'
+
+module Faraday
+  # AdapterRegistry registers adapter class names so they can be looked up by a
+  # String or Symbol name.
+  class AdapterRegistry
+    def initialize
+      @lock = Monitor.new
+      @constants = nil
+    end
+
+    def get(name)
+      klass = @constants && @constants[name]
+      return klass if klass
+
+      klass =
+        if name.respond_to?(:constantize)
+          name.constantize
+        else
+          Object.const_get(name)
+        end
+
+      set(klass, name)
+
+      klass
+    end
+
+    def set(klass, name = nil)
+      name ||= klass.to_s
+      @lock.synchronize do
+        @constants ||= {}
+        @constants[name] = klass
+      end
+    end
+  end
+end