Centralize Abstraction for Thumbnail Generation

[mbarnett]

Right now we call ActiveStorage's variant and preview methods in a variety of places , with inconsistent error handling. This is leading to issues where an invalid or corrupted JPEG or other unknown format issue can lead to a page or search 500ing when it attempts to display a thumbnail for the file.

Arguably, calling into ActiveStorage for variants through the items and theses and communitiers and drafts that own these files is a law of demeter violation, and it's that anti-pattern that's at the root of our inability to correctly handle these errors. We should set up a single "clearing house" method for thumbnails across models that can abstract away the variant generation and handle errors consistently and easily.

If you're going to work on this please grab @mbarnett so that we can whiteboard out approaches and come up with a good, scalable solution that will serve us well down the road.

[pgwillia]

Some related tickets #1129 and #898

[pgwillia]

jupiter/app/models/community.rb

Lines 51 to 56 in 6c44b32

	# compatibility with item thumbnail API
	def thumbnail_path(args = { resize: '100x100', auto_orient: true })
	return nil if logo_attachment.blank?
	Rails.application.routes.url_helpers.rails_representation_path(logo_attachment.variant(args).processed)
	end

jupiter/app/models/jupiter_core/depositable.rb

Lines 99 to 118 in 2877fcb

	# this method came with us from LockedLdpObject, and it'll keep this name until it gets refactored
	# rubocop:disable Naming/AccessorMethodName
	def set_thumbnail(attachment)
	self.logo_id = attachment.id
	save!
	end
	# rubocop:enable Naming/AccessorMethodName
	def thumbnail_path(args = { resize: '100x100', auto_orient: true })
	logo = files.find_by(id: logo_id)
	return nil if logo.blank?
	Rails.application.routes.url_helpers.rails_representation_path(logo.variant(args).processed)
	rescue ActiveStorage::InvariableError
	begin
	Rails.application.routes.url_helpers.rails_representation_path(logo.preview(args).processed)
	rescue ActiveStorage::UnpreviewableError
	nil
	end
	end

jupiter/app/models/concerns/draft_properties.rb

Lines 53 to 64 in be07bda

	# compatibility with the thumbnail API used in Items/Theses and Communities
	def thumbnail_path(args = { resize: '100x100', auto_orient: true })
	return nil unless thumbnail.present? && thumbnail.blob.present?
	Rails.application.routes.url_helpers.rails_representation_path(thumbnail.variant(args).processed)
	rescue ActiveStorage::InvariableError
	begin
	Rails.application.routes.url_helpers.rails_representation_path(thumbnail.preview(args).processed)
	rescue ActiveStorage::UnpreviewableError
	nil
	end
	end

jupiter/app/views/items/draft/_thumbnail.html.erb

Lines 2 to 17 in f9c878a

	<%# NOTE: This is superficially similar to the logic in DraftItem#thumbnail, but this file is run against
	every file attached to an item via a JS callback rendering files/update_files_list.js.erb calling _files_list.html.erb
	whereas DraftItem#thumbnail specifically only deals with rendering the designated file for representing it as a
	thumbnail and is used on various other pages, like profiles, which use the application/_thumbnail partial.%>
	<% thumbnail = rails_representation_path(file.variant(resize: '100x100', auto_orient: true).processed) %>
	<%= safe_thumbnail_tag(thumbnail, alt: '', title: file.filename, size: '100x100') %>
	<% rescue ActiveStorage::InvariableError %>
	<% begin %>
	<% thumbnail = rails_representation_path(file.preview(resize: '100x100', auto_orient: true).processed) %>
	<%= safe_thumbnail_tag(thumbnail, alt: '', title: file.filename, size: '100x100') %>
	<% rescue ActiveStorage::UnpreviewableError %>
	<div class="text-muted text-center img-thumbnail p-3">
	<%= icon('far', file_icon(file.content_type), class: 'fa-5x') %>
	<span class="sr-only"><%= file.filename %></span>
	</div>
	<% end %>

jupiter/app/views/admin/theses/draft/_thumbnail.html.erb

Lines 2 to 17 in f9c878a

	<%# NOTE: This is superficially similar to the logic in DraftItem#thumbnail, but this file is run against
	every file attached to an item via a JS callback rendering files/update_files_list.js.erb calling _files_list.html.erb
	whereas DraftItem#thumbnail specifically only deals with rendering the designated file for representing it as a
	thumbnail and is used on various other pages, like profiles, which use the application/_thumbnail partial.%>
	<% thumbnail = rails_representation_path(file.variant(resize: '100x100', auto_orient: true).processed) %>
	<%= safe_thumbnail_tag(thumbnail, alt: '', title: file.filename, size: '100x100') %>
	<% rescue ActiveStorage::InvariableError %>
	<% begin %>
	<% thumbnail = rails_representation_path(file.preview(resize: '100x100', auto_orient: true).processed) %>
	<%= safe_thumbnail_tag(thumbnail, alt: '', title: file.filename, size: '100x100') %>
	<% rescue ActiveStorage::UnpreviewableError %>
	<div class="text-muted text-center img-thumbnail p-3">
	<%= icon('far', file_icon(file.content_type), class: 'fa-5x') %>
	<span class="sr-only"><%= file.filename %></span>
	</div>
	<% end %>

[pgwillia]

Here's the rough approach:

• Community, Depositable and DraftProperties all get an instance method #logo
• ImagesHelper gets a new method #logo_path which does the error_handling and rollbar reporting
• views call logo_path(item.logo)

[pgwillia]

Merged into postmigration branch.