1 files changed, 130 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/dynamic_matchers.rb b/activerecord/lib/active_record/dynamic_matchers.rb
new file mode 100644
index 0000000000..e278e62ce7
--- /dev/null
+++ b/activerecord/lib/active_record/dynamic_matchers.rb
@@ -0,0 +1,130 @@
+module ActiveRecord
+  module DynamicMatchers #:nodoc:
+    # This code in this file seems to have a lot of indirection, but the indirection
+    # is there to provide extension points for the active_record_deprecated_finders
+    # gem. When we stop supporting active_record_deprecated_finders (from Rails 5),
+    # then we can remove the indirection.
+
+    def respond_to?(name, include_private = false)
+      match = Method.match(self, name)
+      match && match.valid? || super
+    end
+
+    private
+
+    def method_missing(name, *arguments, &block)
+      match = Method.match(self, name)
+
+      if match && match.valid?
+        match.define
+        send(name, *arguments, &block)
+      else
+        super
+      end
+    end
+
+    class Method
+      @matchers = []
+
+      class << self
+        attr_reader :matchers
+
+        def match(model, name)
+          klass = matchers.find { |k| name =~ k.pattern }
+          klass.new(model, name) if klass
+        end
+
+        def pattern
+          /^#{prefix}_([_a-zA-Z]\w*)#{suffix}$/
+        end
+
+        def prefix
+          raise NotImplementedError
+        end
+
+        def suffix
+          ''
+        end
+      end
+
+      attr_reader :model, :name, :attribute_names
+
+      def initialize(model, name)
+        @model           = model
+        @name            = name.to_s
+        @attribute_names = @name.match(self.class.pattern)[1].split('_and_')
+      end
+
+      def valid?
+        attribute_names.all? { |name| model.columns_hash[name] || model.reflect_on_aggregation(name.to_sym) }
+      end
+
+      def define
+        model.class_eval <<-CODE, __FILE__, __LINE__ + 1
+          def self.#{name}(#{signature})
+            #{body}
+          end
+        CODE
+      end
+
+      def body
+        raise NotImplementedError
+      end
+    end
+
+    module Finder
+      # Extended in active_record_deprecated_finders
+      def body
+        result
+      end
+
+      # Extended in active_record_deprecated_finders
+      def result
+        "#{finder}(#{attributes_hash})"
+      end
+
+      # Extended in active_record_deprecated_finders
+      def signature
+        attribute_names.join(', ')
+      end
+
+      def attributes_hash
+        "{" + attribute_names.map { |name| ":#{name} => #{name}" }.join(',') + "}"
+      end
+
+      def finder
+        raise NotImplementedError
+      end
+    end
+
+    class FindBy < Method
+      Method.matchers << self
+      include Finder
+
+      def self.prefix
+        "find_by"
+      end
+
+      def finder
+        "find_by"
+      end
+    end
+
+    class FindByBang < Method
+      Method.matchers << self
+      include Finder
+
+      def self.prefix
+        "find_by"
+      end
+
+      def self.suffix
+        "!"
+      end
+
+      def finder
+        "find_by!"
+      end
+    end
+  end
+end