Started on ActiveStorage matchers

lib/shoulda/matchers/active_record.rb

@@ -23,6 +23,7 @@
 require "shoulda/matchers/active_record/define_enum_for_matcher"
 require "shoulda/matchers/active_record/uniqueness"
 require "shoulda/matchers/active_record/validate_uniqueness_of_matcher"
+require "shoulda/matchers/active_record/have_attached_matcher"
 
 module Shoulda
   module Matchers

lib/shoulda/matchers/active_record/have_attached_matcher.rb

@@ -0,0 +1,147 @@
+module Shoulda
+  module Matchers
+    module ActiveRecord
+      def have_one_attached(name)
+        HaveAttachedMatcher.new(:one, name)
+      end
+
+      def have_many_attached(name)
+        HaveAttachedMatcher.new(:many, name)
+      end
+
+      # @private
+      class HaveAttachedMatcher
+        attr_reader :name
+
+        def initialize(macro, name)
+          @macro = macro
+          @name = name
+        end
+
+        def description
+          "have a has_#{macro}_attached called #{name}"
+        end
+
+        def failure_message
+          <<-MESSAGE
+Expected #{expectation}, but this could not be proved.
+  #{@failure}
+          MESSAGE
+        end
+
+        def failure_message_when_negated
+          <<-MESSAGE
+Did not expect #{expectation}, but it does.
+          MESSAGE
+        end
+
+        def expectation
+          "#{model_class.name} to #{description}"
+        end
+
+        def matches?(subject)
+          @subject = subject
+          reader_attribute_exists? &&
+            writer_attribute_exists? &&
+            attachments_association_exists? &&
+            blobs_association_exists? &&
+            eager_loading_scope_exists?
+        end
+
+        private
+
+        attr_reader :subject, :macro
+
+        def reader_attribute_exists?
+          if subject.respond_to?(name)
+            true
+          else
+            @failure = "#{model_class.name} does not have a :#{name} method."
+            false
+          end
+        end
+
+        def writer_attribute_exists?
+          if subject.respond_to?("#{name}=")
+            true
+          else
+            @failure = "#{model_class.name} does not have a :#{name}= method."
+            false
+          end
+        end
+
+        def attachments_association_exists?
+          if attachments_association_matcher.matches?(subject)
+            true
+          else
+            @failure = attachments_association_matcher.failure_message
+            false
+          end
+        end
+
+        def attachments_association_matcher
+          @_attachments_association_matcher ||=
+            AssociationMatcher.new(
+              :"has_#{macro}",
+              attachments_association_name,
+            ).
+              conditions(name: name).
+              class_name('ActiveStorage::Attachment').
+              inverse_of(:record)
+        end
+
+        def attachments_association_name
+          case macro
+          when :one then
+            "#{name}_attachment"
+          when :many then
+            "#{name}_attachments"
+          end
+        end
+
+        def blobs_association_exists?
+          if blobs_association_matcher.matches?(subject)
+            true
+          else
+            @failure = blobs_association_matcher.failure_message
+            false
+          end
+        end
+
+        def blobs_association_matcher
+          @_blobs_association_matcher ||=
+            AssociationMatcher.new(
+              :"has_#{macro}",
+              blobs_association_name,
+            ).
+              through(attachments_association_name).
+              class_name('ActiveStorage::Blob').
+              source(:blob)
+        end
+
+        def blobs_association_name
+          case macro
+          when :one then
+            "#{name}_blob"
+          when :many then
+            "#{name}_blobs"
+          end
+        end
+
+        def eager_loading_scope_exists?
+          if model_class.respond_to?("with_attached_#{name}")
+            true
+          else
+            @failure = "#{model_class.name} does not have a " \
+                       ":with_attached_#{name} scope."
+            false
+          end
+        end
+
+        def model_class
+          subject.class
+        end
+      end
+    end
+  end
+end

spec/support/unit/helpers/active_record_versions.rb

@@ -47,6 +47,10 @@ def active_record_supports_expression_indexes?
       active_record_version >= 5
     end
 
+    def active_record_supports_active_storage?
+      active_record_version >= 5.2
+    end
+
     def active_record_supports_validate_presence_on_active_storage?
       active_record_version >= '6.0.0.beta1'
     end

spec/support/unit/helpers/rails_versions.rb

@@ -18,5 +18,9 @@ def rails_lt_5?
     def rails_5_x?
       rails_version =~ '~> 5.0'
     end
+
+    def rails_gte_5_2?
+      rails_version >= 5.2
+    end
   end
 end