Extend image_tag to accept ActiveStorage Attachments and Variants (#30084)

* Extend image_tag to accept ActiveStorage's Attachments and Variants

* Flip resolve_image_source around

* Add tests for the new use-cases of image_tag

* Remove the higher-level test

* Update image_tag documentation

* Add error states into the test suite

* Re-raise polymorhic_url's NoMethodError as ArgumentError

* delegate_missing_to will raise DelegationError instead of NoMethodError

2 files changed, 23 insertions, 5 deletions

diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index 66e31978c6..82b0fcbf2e 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -200,7 +200,7 @@ module ActionView
       end
 
       # Returns an HTML image tag for the +source+. The +source+ can be a full
-      # path or a file.
+      # path, a file or an Active Storage attachment.
       #
       # ==== Options
       #
@@ -217,6 +217,8 @@ module ActionView
       #
       # ==== Examples
       #
+      # Assets (images that are part of your app):
+      #
       #   image_tag("icon")
       #   # => <img alt="Icon" src="/assets/icon" />
       #   image_tag("icon.png")
@@ -235,12 +237,21 @@ module ActionView
       #   # => <img src="/assets/icon.png" srcset="/assets/icon_2x.png 2x, /assets/icon_4x.png 4x">
       #   image_tag("pic.jpg", srcset: [["pic_1024.jpg", "1024w"], ["pic_1980.jpg", "1980w"]], sizes: "100vw")
       #   # => <img src="/assets/pic.jpg" srcset="/assets/pic_1024.jpg 1024w, /assets/pic_1980.jpg 1980w" sizes="100vw">
+      #
+      # Active Storage (images that are uploaded by the users of your app):
+      #
+      #   image_tag(user.avatar)
+      #   # => <img src="/rails/active_storage/blobs/.../tiger.jpg" alt="Tiger" />
+      #   image_tag(user.avatar.variant(resize: "100x100"))
+      #   # => <img src="/rails/active_storage/variants/.../tiger.jpg" alt="Tiger" />
+      #   image_tag(user.avatar.variant(resize: "100x100"), size: '100')
+      #   # => <img width="100" height="100" src="/rails/active_storage/variants/.../tiger.jpg" alt="Tiger" />
       def image_tag(source, options = {})
         options = options.symbolize_keys
         check_for_image_tag_errors(options)
         skip_pipeline = options.delete(:skip_pipeline)
 
-        src = options[:src] = path_to_image(source, skip_pipeline: skip_pipeline)
+        src = options[:src] = resolve_image_source(source, skip_pipeline)
 
         unless src.start_with?("cid:") || src.start_with?("data:") || src.blank?
           options[:alt] = options.fetch(:alt) { image_alt(src) }
@@ -364,6 +375,16 @@ module ActionView
           end
         end
 
+        def resolve_image_source(source, skip_pipeline)
+          if source.is_a?(Symbol) || source.is_a?(String)
+            path_to_image(source, skip_pipeline: skip_pipeline)
+          else
+            polymorphic_url(source)
+          end
+        rescue NoMethodError => e
+          raise ArgumentError, "Can't resolve image into URL: #{e}"
+        end
+
         def extract_dimensions(size)
           size = size.to_s
           if /\A\d+x\d+\z/.match?(size)
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 4d312d3b6d..5b8e50cc5e 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -565,9 +565,6 @@ class AssetTagHelperTest < ActionView::TestCase
     def blank?; true; end
     def to_s; "no-image-yet.png"; end
   end
-  def test_image_tag_with_blank_placeholder
-    assert_equal '<img alt="" src="/images/no-image-yet.png" />', image_tag(PlaceholderImage.new, alt: "")
-  end
   def test_image_path_with_blank_placeholder
     assert_equal "/images/no-image-yet.png", image_path(PlaceholderImage.new)
   end