Fixing image lfs bug and also displaying text lfs

This commit, introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/23812,
fixes a problem creating a displaying image diff notes when the image
is stored in LFS. The main problem was that `Gitlab::Diff::File` was
returning an invalid valid in `text?` for this kind of files.

It also fixes a rendering problem with other LFS files, like text
ones. They LFS pointer shouldn't be shown when LFS is enabled
for the project, but they were.

35 files changed, 298 insertions, 154 deletions

diff --git a/app/assets/javascripts/diffs/components/diff_content.vue b/app/assets/javascripts/diffs/components/diff_content.vue
index 42d09e44768..ba6dcd63880 100644
--- a/app/assets/javascripts/diffs/components/diff_content.vue
+++ b/app/assets/javascripts/diffs/components/diff_content.vue
@@ -45,6 +45,9 @@ export default {
     isTextFile() {
       return this.diffFile.viewer.name === 'text';
     },
+    errorMessage() {
+      return this.diffFile.viewer.error;
+    },
     diffFileCommentForm() {
       return this.getCommentFormForDiffFile(this.diffFile.file_hash);
     },
@@ -75,7 +78,7 @@ export default {
 
 <template>
   <div class="diff-content">
-    <div class="diff-viewer">
+    <div v-if="!errorMessage" class="diff-viewer">
       <template v-if="isTextFile">
         <empty-file-viewer v-if="diffFile.empty" />
         <inline-diff-view
@@ -129,5 +132,8 @@ export default {
         </div>
       </diff-viewer>
     </div>
+    <div v-else class="diff-viewer">
+      <div class="nothing-here-block" v-html="errorMessage"></div>
+    </div>
   </div>
 </template>
diff --git a/app/controllers/projects/blob_controller.rb b/app/controllers/projects/blob_controller.rb
index 60fabd15333..ff286c0ccf0 100644
--- a/app/controllers/projects/blob_controller.rb
+++ b/app/controllers/projects/blob_controller.rb
@@ -260,7 +260,7 @@ class Projects::BlobController < Projects::ApplicationController
       extension: blob.extension,
       size: blob.raw_size,
       mime_type: blob.mime_type,
-      binary: blob.raw_binary?,
+      binary: blob.binary?,
       simple_viewer: blob.simple_viewer&.class&.partial_name,
       rich_viewer: blob.rich_viewer&.class&.partial_name,
       show_viewer_switcher: !!blob.show_viewer_switcher?,
diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index 4c8e1b209c0..3dea0975beb 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -193,7 +193,7 @@ module BlobHelper
 
   def open_raw_blob_button(blob)
     return if blob.empty?
-    return if blob.raw_binary? || blob.stored_externally?
+    return if blob.binary? || blob.stored_externally?
 
     title = 'Open raw'
     link_to icon('file-code-o'), blob_raw_path, class: 'btn btn-sm has-tooltip', target: '_blank', rel: 'noopener noreferrer', title: title, data: { container: 'body' }
diff --git a/app/helpers/diff_helper.rb b/app/helpers/diff_helper.rb
index b6844d36052..32431959851 100644
--- a/app/helpers/diff_helper.rb
+++ b/app/helpers/diff_helper.rb
@@ -138,30 +138,6 @@ module DiffHelper
     !diff_file.deleted_file? && @merge_request && @merge_request.source_project
   end
 
-  def diff_render_error_reason(viewer)
-    case viewer.render_error
-    when :too_large
-      "it is too large"
-    when :server_side_but_stored_externally
-      case viewer.diff_file.external_storage
-      when :lfs
-        'it is stored in LFS'
-      else
-        'it is stored externally'
-      end
-    end
-  end
-
-  def diff_render_error_options(viewer)
-    diff_file = viewer.diff_file
-    options = []
-
-    blob_url = project_blob_path(@project, tree_join(diff_file.content_sha, diff_file.file_path))
-    options << link_to('view the blob', blob_url)
-
-    options
-  end
-
   def diff_file_changed_icon(diff_file)
     if diff_file.deleted_file?
       "file-deletion"
diff --git a/app/helpers/snippets_helper.rb b/app/helpers/snippets_helper.rb
index c7d31f3469d..8fded0efe4d 100644
--- a/app/helpers/snippets_helper.rb
+++ b/app/helpers/snippets_helper.rb
@@ -110,7 +110,7 @@ module SnippetsHelper
 
   def embedded_snippet_raw_button
     blob = @snippet.blob
-    return if blob.empty? || blob.raw_binary? || blob.stored_externally?
+    return if blob.empty? || blob.binary? || blob.stored_externally?
 
     snippet_raw_url = if @snippet.is_a?(PersonalSnippet)
                         raw_snippet_url(@snippet)
diff --git a/app/models/blob.rb b/app/models/blob.rb
index 66a0925c495..c5766eb0327 100644
--- a/app/models/blob.rb
+++ b/app/models/blob.rb
@@ -102,7 +102,7 @@ class Blob < SimpleDelegator
   # If the blob is a text based blob the content is converted to UTF-8 and any
   # invalid byte sequences are replaced.
   def data
-    if binary?
+    if binary_in_repo?
       super
     else
       @data ||= super.encode(Encoding::UTF_8, invalid: :replace, undef: :replace)
@@ -149,7 +149,7 @@ class Blob < SimpleDelegator
   # an LFS pointer, we assume the file stored in LFS is binary, unless a
   # text-based rich blob viewer matched on the file's extension. Otherwise, this
   # depends on the type of the blob itself.
-  def raw_binary?
+  def binary?
     if stored_externally?
       if rich_viewer
         rich_viewer.binary?
@@ -161,7 +161,7 @@ class Blob < SimpleDelegator
         true
       end
     else
-      binary?
+      binary_in_repo?
     end
   end
 
@@ -180,7 +180,7 @@ class Blob < SimpleDelegator
   end
 
   def readable_text?
-    text? && !stored_externally? && !truncated?
+    text_in_repo? && !stored_externally? && !truncated?
   end
 
   def simple_viewer
@@ -220,7 +220,7 @@ class Blob < SimpleDelegator
   def simple_viewer_class
     if empty?
       BlobViewer::Empty
-    elsif raw_binary?
+    elsif binary?
       BlobViewer::Download
     else # text
       BlobViewer::Text
diff --git a/app/models/blob_viewer/base.rb b/app/models/blob_viewer/base.rb
index eaaf9af1330..df6b9bb2f0b 100644
--- a/app/models/blob_viewer/base.rb
+++ b/app/models/blob_viewer/base.rb
@@ -16,7 +16,7 @@ module BlobViewer
 
     def initialize(blob)
       @blob = blob
-      @initially_binary = blob.binary?
+      @initially_binary = blob.binary_in_repo?
     end
 
     def self.partial_path
@@ -52,7 +52,7 @@ module BlobViewer
     end
 
     def self.can_render?(blob, verify_binary: true)
-      return false if verify_binary && binary? != blob.binary?
+      return false if verify_binary && binary? != blob.binary_in_repo?
       return true if extensions&.include?(blob.extension)
       return true if file_types&.include?(blob.file_type)
 
@@ -72,7 +72,7 @@ module BlobViewer
     end
 
     def binary_detected_after_load?
-      !@initially_binary && blob.binary?
+      !@initially_binary && blob.binary_in_repo?
     end
 
     # This method is used on the server side to check whether we can attempt to
diff --git a/app/models/concerns/blob_like.rb b/app/models/concerns/blob_like.rb
index f20f01486a5..dc80f8d62f4 100644
--- a/app/models/concerns/blob_like.rb
+++ b/app/models/concerns/blob_like.rb
@@ -28,7 +28,7 @@ module BlobLike
     nil
   end
 
-  def binary?
+  def binary_in_repo?
     false
   end
 
diff --git a/app/models/diff_viewer/base.rb b/app/models/diff_viewer/base.rb
index 1176861a827..527ee33b83b 100644
--- a/app/models/diff_viewer/base.rb
+++ b/app/models/diff_viewer/base.rb
@@ -18,7 +18,7 @@ module DiffViewer
 
     def initialize(diff_file)
       @diff_file = diff_file
-      @initially_binary = diff_file.binary?
+      @initially_binary = diff_file.binary_in_repo?
     end
 
     def self.partial_path
@@ -48,7 +48,7 @@ module DiffViewer
 
     def self.can_render_blob?(blob, verify_binary: true)
       return true if blob.nil?
-      return false if verify_binary && binary? != blob.binary?
+      return false if verify_binary && binary? != blob.binary_in_repo?
       return true if extensions&.include?(blob.extension)
       return true if file_types&.include?(blob.file_type)
 
@@ -70,20 +70,49 @@ module DiffViewer
     end
 
     def binary_detected_after_load?
-      !@initially_binary && diff_file.binary?
+      !@initially_binary && diff_file.binary_in_repo?
     end
 
     # This method is used on the server side to check whether we can attempt to
-    # render the diff_file at all. Human-readable error messages are found in the
-    # `BlobHelper#diff_render_error_reason` helper.
+    # render the diff_file at all. The human-readable error message can be
+    # retrieved by #render_error_message.
     def render_error
       if too_large?
         :too_large
       end
     end
 
+    def render_error_message
+      return unless render_error
+
+      _("This %{viewer} could not be displayed because %{reason}. You can %{options} instead.") %
+        {
+          viewer: switcher_title,
+          reason: render_error_reason,
+          options: render_error_options.to_sentence(two_words_connector: _(' or '), last_word_connector: _(', or '))
+        }
+    end
+
     def prepare!
       # To be overridden by subclasses
     end
+
+    private
+
+    def render_error_options
+      options = []
+
+      blob_url = Gitlab::Routing.url_helpers.project_blob_path(diff_file.repository.project,
+                                                               File.join(diff_file.content_sha, diff_file.file_path))
+      options << ActionController::Base.helpers.link_to(_('view the blob'), blob_url)
+
+      options
+    end
+
+    def render_error_reason
+      if render_error == :too_large
+        _("it is too large")
+      end
+    end
   end
 end
diff --git a/app/models/diff_viewer/image.rb b/app/models/diff_viewer/image.rb
index c356c2ca50e..350bef1d42a 100644
--- a/app/models/diff_viewer/image.rb
+++ b/app/models/diff_viewer/image.rb
@@ -9,6 +9,6 @@ module DiffViewer
     self.extensions = UploaderHelper::IMAGE_EXT
     self.binary = true
     self.switcher_icon = 'picture-o'
-    self.switcher_title = 'image diff'
+    self.switcher_title = _('image diff')
   end
 end
diff --git a/app/models/diff_viewer/rich.rb b/app/models/diff_viewer/rich.rb
index 2faa1be6567..5caefa2031c 100644
--- a/app/models/diff_viewer/rich.rb
+++ b/app/models/diff_viewer/rich.rb
@@ -7,7 +7,7 @@ module DiffViewer
     included do
       self.type = :rich
       self.switcher_icon = 'file-text-o'
-      self.switcher_title = 'rendered diff'
+      self.switcher_title = _('rendered diff')
     end
   end
 end
diff --git a/app/models/diff_viewer/server_side.rb b/app/models/diff_viewer/server_side.rb
index 977204e6c97..0877c9dddec 100644
--- a/app/models/diff_viewer/server_side.rb
+++ b/app/models/diff_viewer/server_side.rb
@@ -24,5 +24,17 @@ module DiffViewer
 
       super
     end
+
+    private
+
+    def render_error_reason
+      return super unless render_error == :server_side_but_stored_externally
+
+      if diff_file.external_storage == :lfs
+        _('it is stored in LFS')
+      else
+        _('it is stored externally')
+      end
+    end
   end
 end
diff --git a/app/models/diff_viewer/simple.rb b/app/models/diff_viewer/simple.rb
index 8d28ca5239a..929d8ad5a7e 100644
--- a/app/models/diff_viewer/simple.rb
+++ b/app/models/diff_viewer/simple.rb
@@ -7,7 +7,7 @@ module DiffViewer
     included do
       self.type = :simple
       self.switcher_icon = 'code'
-      self.switcher_title = 'source diff'
+      self.switcher_title = _('source diff')
     end
   end
 end
diff --git a/app/serializers/diff_viewer_entity.rb b/app/serializers/diff_viewer_entity.rb
index 27fba03cb3f..587fa2347fd 100644
--- a/app/serializers/diff_viewer_entity.rb
+++ b/app/serializers/diff_viewer_entity.rb
@@ -4,4 +4,7 @@ class DiffViewerEntity < Grape::Entity
   # Partial name refers directly to a Rails feature, let's avoid
   # using this on the frontend.
   expose :partial_name, as: :name
+  expose :error do |diff_viewer|
+    diff_viewer.render_error_message
+  end
 end
diff --git a/app/views/projects/diffs/_render_error.html.haml b/app/views/projects/diffs/_render_error.html.haml
index c3dc47a56a7..7dbd9897e83 100644
--- a/app/views/projects/diffs/_render_error.html.haml
+++ b/app/views/projects/diffs/_render_error.html.haml
@@ -1,6 +1,2 @@
 .nothing-here-block
-  = _("This %{viewer} could not be displayed because %{reason}.") % { viewer: viewer.switcher_title, reason: diff_render_error_reason(viewer) }
-
-  You can
-  = diff_render_error_options(viewer).to_sentence(two_words_connector: ' or ', last_word_connector: ', or ').html_safe
-  instead.
+  = viewer.render_error_message.html_safe
diff --git a/changelogs/unreleased/fj-fix-lfs-image-comments-diffs.yml b/changelogs/unreleased/fj-fix-lfs-image-comments-diffs.yml
new file mode 100644
index 00000000000..dc1fe5d7417
--- /dev/null
+++ b/changelogs/unreleased/fj-fix-lfs-image-comments-diffs.yml
@@ -0,0 +1,5 @@
+---
+title: Fix bug commenting on LFS images
+merge_request: 23812
+author:
+type: fixed
diff --git a/lib/gitlab/blob_helper.rb b/lib/gitlab/blob_helper.rb
index 488c1d85387..d3e15a79a8b 100644
--- a/lib/gitlab/blob_helper.rb
+++ b/lib/gitlab/blob_helper.rb
@@ -12,7 +12,7 @@ module Gitlab
     end
 
     def viewable?
-      !large? && text?
+      !large? && text_in_repo?
     end
 
     MEGABYTE = 1024 * 1024
@@ -21,7 +21,7 @@ module Gitlab
       size.to_i > MEGABYTE
     end
 
-    def binary?
+    def binary_in_repo?
       # Large blobs aren't even loaded into memory
       if data.nil?
         true
@@ -40,8 +40,8 @@ module Gitlab
       end
     end
 
-    def text?
-      !binary?
+    def text_in_repo?
+      !binary_in_repo?
     end
 
     def image?
@@ -113,7 +113,7 @@ module Gitlab
     def content_type
       # rubocop:disable Style/MultilineTernaryOperator
       # rubocop:disable Style/NestedTernaryOperator
-      @content_type ||= binary_mime_type? || binary? ? mime_type :
+      @content_type ||= binary_mime_type? || binary_in_repo? ? mime_type :
                           (encoding ? "text/plain; charset=#{encoding.downcase}" : "text/plain")
       # rubocop:enable Style/NestedTernaryOperator
       # rubocop:enable Style/MultilineTernaryOperator
diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index bcbded6be9a..e410d5a8333 100644
--- a/lib/gitlab/diff/file.rb
+++ b/lib/gitlab/diff/file.rb
@@ -3,6 +3,8 @@
 module Gitlab
   module Diff
     class File
+      include Gitlab::Utils::StrongMemoize
+
       attr_reader :diff, :repository, :diff_refs, :fallback_diff_refs, :unique_identifier
 
       delegate :new_file?, :deleted_file?, :renamed_file?,
@@ -232,12 +234,12 @@ module Gitlab
         repository.attributes(file_path).fetch('diff') { true }
       end
 
-      def binary?
-        has_binary_notice? || try_blobs(:binary?)
+      def binary_in_repo?
+        has_binary_notice? || try_blobs(:binary_in_repo?)
       end
 
-      def text?
-        !binary?
+      def text_in_repo?
+        !binary_in_repo?
       end
 
       def external_storage_error?
@@ -279,12 +281,16 @@ module Gitlab
         valid_blobs.map(&:empty?).all?
       end
 
-      def raw_binary?
-        try_blobs(:raw_binary?)
+      def binary?
+        strong_memoize(:is_binary) do
+          try_blobs(:binary?)
+        end
       end
 
-      def raw_text?
-        !raw_binary? && !different_type?
+      def text?
+        strong_memoize(:is_text) do
+          !binary? && !different_type?
+        end
       end
 
       def simple_viewer
@@ -367,19 +373,19 @@ module Gitlab
         return DiffViewer::NotDiffable unless diffable?
 
         if content_changed?
-          if raw_text?
+          if text?
             DiffViewer::Text
           else
             DiffViewer::NoPreview
           end
         elsif new_file?
-          if raw_text?
+          if text?
             DiffViewer::Text
           else
             DiffViewer::Added
           end
         elsif deleted_file?
-          if raw_text?
+          if text?
             DiffViewer::Text
           else
             DiffViewer::Deleted
diff --git a/lib/gitlab/git/blob.rb b/lib/gitlab/git/blob.rb
index 2d25389594e..259a2b7911a 100644
--- a/lib/gitlab/git/blob.rb
+++ b/lib/gitlab/git/blob.rb
@@ -100,7 +100,7 @@ module Gitlab
         @loaded_all_data = @loaded_size == size
       end
 
-      def binary?
+      def binary_in_repo?
         @binary.nil? ? super : @binary == true
       end
 
@@ -174,7 +174,7 @@ module Gitlab
       private
 
       def has_lfs_version_key?
-        !empty? && text? && data.start_with?("version https://git-lfs.github.com/spec")
+        !empty? && text_in_repo? && data.start_with?("version https://git-lfs.github.com/spec")
       end
     end
   end
diff --git a/locale/gitlab.pot b/locale/gitlab.pot
index b27efe04966..bd0f2b5d122 100644
--- a/locale/gitlab.pot
+++ b/locale/gitlab.pot
@@ -19,6 +19,9 @@ msgstr ""
 msgid " Status"
 msgstr ""
 
+msgid " or "
+msgstr ""
+
 msgid "%d addition"
 msgid_plural "%d additions"
 msgstr[0] ""
@@ -185,6 +188,9 @@ msgstr ""
 msgid "+ %{moreCount} more"
 msgstr ""
 
+msgid ", or "
+msgstr ""
+
 msgid "- Runner is active and can process any new jobs"
 msgstr ""
 
@@ -6698,7 +6704,7 @@ msgstr ""
 msgid "Third party offers"
 msgstr ""
 
-msgid "This %{viewer} could not be displayed because %{reason}."
+msgid "This %{viewer} could not be displayed because %{reason}. You can %{options} instead."
 msgstr ""
 
 msgid "This GitLab instance does not provide any shared Runners yet. Instance administrators can register shared Runners in the admin area."
@@ -7888,6 +7894,9 @@ msgstr ""
 msgid "https://your-bitbucket-server"
 msgstr ""
 
+msgid "image diff"
+msgstr ""
+
 msgid "import flow"
 msgstr ""
 
@@ -7900,6 +7909,15 @@ msgstr ""
 msgid "issue boards"
 msgstr ""
 
+msgid "it is stored externally"
+msgstr ""
+
+msgid "it is stored in LFS"
+msgstr ""
+
+msgid "it is too large"
+msgstr ""
+
 msgid "latest deployment"
 msgstr ""
 
@@ -8140,6 +8158,9 @@ msgstr ""
 msgid "remove due date"
 msgstr ""
 
+msgid "rendered diff"
+msgstr ""
+
 msgid "reply"
 msgid_plural "replies"
 msgstr[0] ""
@@ -8151,6 +8172,9 @@ msgstr ""
 msgid "source"
 msgstr ""
 
+msgid "source diff"
+msgstr ""
+
 msgid "spendCommand|%{slash_command} will update the sum of the time spent."
 msgstr ""
 
@@ -8172,6 +8196,9 @@ msgstr ""
 msgid "view it on GitLab"
 msgstr ""
 
+msgid "view the blob"
+msgstr ""
+
 msgid "with %{additions} additions, %{deletions} deletions."
 msgstr ""
 
diff --git a/spec/features/merge_request/user_creates_image_diff_notes_spec.rb b/spec/features/merge_request/user_creates_image_diff_notes_spec.rb
index d790bdc82ce..d19408ee87f 100644
--- a/spec/features/merge_request/user_creates_image_diff_notes_spec.rb
+++ b/spec/features/merge_request/user_creates_image_diff_notes_spec.rb
@@ -90,9 +90,6 @@ describe 'Merge request > User creates image diff notes', :js do
 
   %w(inline parallel).each do |view|
     context "#{view} view" do
-      let(:merge_request) { create(:merge_request_with_diffs, :with_image_diffs, source_project: project, author: user) }
-      let(:path)          { "files/images/ee_repo_logo.png" }
-
       let(:position) do
         Gitlab::Diff::Position.new(
           old_path: path,
@@ -108,9 +105,11 @@ describe 'Merge request > User creates image diff notes', :js do
 
       let!(:note) { create(:diff_note_on_merge_request, project: project, noteable: merge_request, position: position) }
 
-      describe 'creating a new diff note' do
+      shared_examples 'creates image diff note' do
         before do
           visit diffs_project_merge_request_path(project, merge_request, view: view)
+          wait_for_requests
+
           create_image_diff_note
         end
 
@@ -132,6 +131,32 @@ describe 'Merge request > User creates image diff notes', :js do
           expect(page).to have_content('image diff test comment')
         end
       end
+
+      context 'when images are not stored in LFS' do
+        let(:merge_request) { create(:merge_request_with_diffs, :with_image_diffs, source_project: project, author: user) }
+        let(:path)          { 'files/images/ee_repo_logo.png' }
+
+        it_behaves_like 'creates image diff note'
+      end
+
+      context 'when images are stored in LFS' do
+        let(:merge_request) { create(:merge_request, source_project: project, target_project: project, source_branch: 'png-lfs', target_branch: 'master', author: user) }
+        let(:path)          { 'files/images/logo-black.png' }
+
+        before do
+          allow(Gitlab.config.lfs).to receive(:enabled).and_return(true)
+          project.update_attribute(:lfs_enabled, true)
+        end
+
+        it 'shows lfs badges' do
+          visit diffs_project_merge_request_path(project, merge_request, view: view)
+          wait_for_requests
+
+          expect(page.all('.diff-file span.label-lfs', visible: :all)).not_to be_empty
+        end
+
+        it_behaves_like 'creates image diff note'
+      end
     end
   end
 
diff --git a/spec/features/merge_request/user_sees_diff_spec.rb b/spec/features/merge_request/user_sees_diff_spec.rb
index 0df9e4bbc1a..04b07525919 100644
--- a/spec/features/merge_request/user_sees_diff_spec.rb
+++ b/spec/features/merge_request/user_sees_diff_spec.rb
@@ -87,20 +87,6 @@ describe 'Merge request > User sees diff', :js do
       let(:current_user) { project.owner }
       let(:branch_name) {"test_branch"}
 
-      def create_file(branch_name, file_name, content)
-        Files::CreateService.new(
-          project,
-          current_user,
-          start_branch: branch_name,
-          branch_name: branch_name,
-          commit_message: "Create file",
-          file_path: file_name,
-          file_content: content
-        ).execute
-
-        project.commit(branch_name)
-      end
-
       it 'escapes any HTML special characters in the diff chunk header' do
         file_content =
           <<~CONTENT
@@ -136,5 +122,61 @@ describe 'Merge request > User sees diff', :js do
         expect(page).to have_css(".line[lang='rust'] .k")
       end
     end
+
+    context 'when file is stored in LFS' do
+      let(:merge_request) { create(:merge_request, source_project: project) }
+      let(:current_user) { project.owner }
+
+      context 'when LFS is enabled on the project' do
+        before do
+          allow(Gitlab.config.lfs).to receive(:enabled).and_return(true)
+          project.update_attribute(:lfs_enabled, true)
+
+          create_file('master', file_name, project.repository.blob_at('master', 'files/lfs/lfs_object.iso').data)
+
+          visit diffs_project_merge_request_path(project, merge_request)
+        end
+
+        context 'when file is an image', :js do
+          let(:file_name) { 'files/lfs/image.png' }
+
+          it 'shows an error message' do
+            expect(page).not_to have_content('could not be displayed because it is stored in LFS')
+          end
+        end
+
+        context 'when file is not an image' do
+          let(:file_name) { 'files/lfs/ruby.rb' }
+
+          it 'shows an error message' do
+            expect(page).to have_content('This source diff could not be displayed because it is stored in LFS')
+          end
+        end
+      end
+
+      context 'when LFS is not enabled' do
+        before do
+          visit diffs_project_merge_request_path(project, merge_request)
+        end
+
+        it 'displays the diff' do
+          expect(page).to have_content('size 1575078')
+        end
+      end
+    end
+
+    def create_file(branch_name, file_name, content)
+      Files::CreateService.new(
+        project,
+        current_user,
+        start_branch: branch_name,
+        branch_name: branch_name,
+        commit_message: "Create file",
+        file_path: file_name,
+        file_content: content
+      ).execute
+
+      project.commit(branch_name)
+    end
   end
 end
diff --git a/spec/features/projects/commits/user_browses_commits_spec.rb b/spec/features/projects/commits/user_browses_commits_spec.rb
index 2159adf49fc..574a8aefd63 100644
--- a/spec/features/projects/commits/user_browses_commits_spec.rb
+++ b/spec/features/projects/commits/user_browses_commits_spec.rb
@@ -93,7 +93,7 @@ describe 'User browses commits' do
 
     it 'shows a blank label' do
       allow_any_instance_of(Gitlab::Diff::File).to receive(:blob).and_return(nil)
-      allow_any_instance_of(Gitlab::Diff::File).to receive(:raw_binary?).and_return(true)
+      allow_any_instance_of(Gitlab::Diff::File).to receive(:binary?).and_return(true)
 
       visit(project_commit_path(project, commit))
 
diff --git a/spec/fixtures/api/schemas/entities/diff_viewer.json b/spec/fixtures/api/schemas/entities/diff_viewer.json
index 19780f49a88..81325cd86c6 100644
--- a/spec/fixtures/api/schemas/entities/diff_viewer.json
+++ b/spec/fixtures/api/schemas/entities/diff_viewer.json
@@ -1,8 +1,20 @@
 {
   "type": "object",
-  "required": ["name"],
+  "required": [
+    "name"
+  ],
   "properties": {
-    "name": { "type": ["string"] }
+    "name": {
+      "type": [
+        "string"
+      ]
+    },
+    "error": {
+      "type": [
+        "string",
+        "null"
+      ]
+    }
   },
   "additionalProperties": false
 }
diff --git a/spec/helpers/diff_helper_spec.rb b/spec/helpers/diff_helper_spec.rb
index 53c010fa0db..5396243f44d 100644
--- a/spec/helpers/diff_helper_spec.rb
+++ b/spec/helpers/diff_helper_spec.rb
@@ -256,43 +256,6 @@ describe DiffHelper do
     end
   end
 
-  context 'viewer related' do
-    let(:viewer) { diff_file.simple_viewer }
-
-    before do
-      assign(:project, project)
-    end
-
-    describe '#diff_render_error_reason' do
-      context 'for error :too_large' do
-        before do
-          expect(viewer).to receive(:render_error).and_return(:too_large)
-        end
-
-        it 'returns an error message' do
-          expect(helper.diff_render_error_reason(viewer)).to eq('it is too large')
-        end
-      end
-
-      context 'for error :server_side_but_stored_externally' do
-        before do
-          expect(viewer).to receive(:render_error).and_return(:server_side_but_stored_externally)
-          expect(diff_file).to receive(:external_storage).and_return(:lfs)
-        end
-
-        it 'returns an error message' do
-          expect(helper.diff_render_error_reason(viewer)).to eq('it is stored in LFS')
-        end
-      end
-    end
-
-    describe '#diff_render_error_options' do
-      it 'includes a "view the blob" link' do
-        expect(helper.diff_render_error_options(viewer)).to include(/view the blob/)
-      end
-    end
-  end
-
   context '#diff_file_path_text' do
     it 'returns full path by default' do
       expect(diff_file_path_text(diff_file)).to eq(diff_file.new_path)
diff --git a/spec/lib/gitlab/blob_helper_spec.rb b/spec/lib/gitlab/blob_helper_spec.rb
index 0b56f8687c3..e057385b35f 100644
--- a/spec/lib/gitlab/blob_helper_spec.rb
+++ b/spec/lib/gitlab/blob_helper_spec.rb
@@ -53,11 +53,11 @@ describe Gitlab::BlobHelper do
 
   describe '#text?' do
     it 'returns true' do
-      expect(blob.text?).to be_truthy
+      expect(blob.text_in_repo?).to be_truthy
     end
 
     it 'returns false' do
-      expect(large_blob.text?).to be_falsey
+      expect(large_blob.text_in_repo?).to be_falsey
     end
   end
 
diff --git a/spec/lib/gitlab/diff/file_spec.rb b/spec/lib/gitlab/diff/file_spec.rb
index b15d22c634a..862590268ca 100644
--- a/spec/lib/gitlab/diff/file_spec.rb
+++ b/spec/lib/gitlab/diff/file_spec.rb
@@ -310,7 +310,7 @@ describe Gitlab::Diff::File do
     context 'when the content changed' do
       context 'when the file represented by the diff file is binary' do
         before do
-          allow(diff_file).to receive(:raw_binary?).and_return(true)
+          allow(diff_file).to receive(:binary?).and_return(true)
         end
 
         it 'returns a No Preview viewer' do
@@ -345,7 +345,7 @@ describe Gitlab::Diff::File do
 
       context 'when the file represented by the diff file is binary' do
         before do
-          allow(diff_file).to receive(:raw_binary?).and_return(true)
+          allow(diff_file).to receive(:binary?).and_return(true)
         end
 
         it 'returns an Added viewer' do
@@ -380,7 +380,7 @@ describe Gitlab::Diff::File do
 
       context 'when the file represented by the diff file is binary' do
         before do
-          allow(diff_file).to receive(:raw_binary?).and_return(true)
+          allow(diff_file).to receive(:binary?).and_return(true)
         end
 
         it 'returns a Deleted viewer' do
@@ -436,7 +436,7 @@ describe Gitlab::Diff::File do
         allow(diff_file).to receive(:deleted_file?).and_return(false)
         allow(diff_file).to receive(:renamed_file?).and_return(false)
         allow(diff_file).to receive(:mode_changed?).and_return(false)
-        allow(diff_file).to receive(:raw_text?).and_return(false)
+        allow(diff_file).to receive(:text?).and_return(false)
       end
 
       it 'returns a No Preview viewer' do
diff --git a/spec/lib/gitlab/diff/lines_unfolder_spec.rb b/spec/lib/gitlab/diff/lines_unfolder_spec.rb
index 8e00c8e0e30..f22c2c90334 100644
--- a/spec/lib/gitlab/diff/lines_unfolder_spec.rb
+++ b/spec/lib/gitlab/diff/lines_unfolder_spec.rb
@@ -185,7 +185,7 @@ describe Gitlab::Diff::LinesUnfolder do
 
   let(:project) { create(:project) }
 
-  let(:old_blob) { Gitlab::Git::Blob.new(data: raw_old_blob) }
+  let(:old_blob) { Blob.decorate(Gitlab::Git::Blob.new(data: raw_old_blob, size: 10)) }
 
   let(:diff) do
     Gitlab::Git::Diff.new(diff: raw_diff,
diff --git a/spec/lib/gitlab/git/blob_spec.rb b/spec/lib/gitlab/git/blob_spec.rb
index 80dd3dcc58e..1bcec04d28f 100644
--- a/spec/lib/gitlab/git/blob_spec.rb
+++ b/spec/lib/gitlab/git/blob_spec.rb
@@ -59,7 +59,7 @@ describe Gitlab::Git::Blob, :seed_helper do
       it { expect(blob.data[0..10]).to eq("*.rbc\n*.sas") }
       it { expect(blob.size).to eq(241) }
       it { expect(blob.mode).to eq("100644") }
-      it { expect(blob).not_to be_binary }
+      it { expect(blob).not_to be_binary_in_repo }
     end
 
     context 'file in root with leading slash' do
@@ -92,7 +92,7 @@ describe Gitlab::Git::Blob, :seed_helper do
       end
 
       it 'does not mark the blob as binary' do
-        expect(blob).not_to be_binary
+        expect(blob).not_to be_binary_in_repo
       end
     end
 
@@ -123,7 +123,7 @@ describe Gitlab::Git::Blob, :seed_helper do
           .with(hash_including(binary: true))
           .and_call_original
 
-        expect(blob).to be_binary
+        expect(blob).to be_binary_in_repo
       end
     end
   end
@@ -196,7 +196,7 @@ describe Gitlab::Git::Blob, :seed_helper do
       it { expect(blob.id).to eq('409f37c4f05865e4fb208c771485f211a22c4c2d') }
       it { expect(blob.data).to eq('') }
       it 'does not mark the blob as binary' do
-        expect(blob).not_to be_binary
+        expect(blob).not_to be_binary_in_repo
       end
     end
 
diff --git a/spec/lib/gitlab/gitaly_client/blobs_stitcher_spec.rb b/spec/lib/gitlab/gitaly_client/blobs_stitcher_spec.rb
index 9db710e759e..742b2872c40 100644
--- a/spec/lib/gitlab/gitaly_client/blobs_stitcher_spec.rb
+++ b/spec/lib/gitlab/gitaly_client/blobs_stitcher_spec.rb
@@ -21,7 +21,7 @@ describe Gitlab::GitalyClient::BlobsStitcher do
       expect(blobs[0].size).to eq(1642)
       expect(blobs[0].commit_id).to eq('f00ba7')
       expect(blobs[0].data).to eq("first-line\nsecond-line")
-      expect(blobs[0].binary?).to be false
+      expect(blobs[0].binary_in_repo?).to be false
 
       expect(blobs[1].id).to eq('abcdef2')
       expect(blobs[1].mode).to eq('100644')
@@ -30,7 +30,7 @@ describe Gitlab::GitalyClient::BlobsStitcher do
       expect(blobs[1].size).to eq(2461)
       expect(blobs[1].commit_id).to eq('f00ba8')
       expect(blobs[1].data).to eq("GIF87a\x90\x01".b)
-      expect(blobs[1].binary?).to be true
+      expect(blobs[1].binary_in_repo?).to be true
     end
   end
 end
diff --git a/spec/models/blob_spec.rb b/spec/models/blob_spec.rb
index e8c03b587e2..05cf242e84d 100644
--- a/spec/models/blob_spec.rb
+++ b/spec/models/blob_spec.rb
@@ -122,14 +122,14 @@ describe Blob do
     end
   end
 
-  describe '#raw_binary?' do
+  describe '#binary?' do
     context 'if the blob is stored externally' do
       context 'if the extension has a rich viewer' do
         context 'if the viewer is binary' do
           it 'returns true' do
             blob = fake_blob(path: 'file.pdf', lfs: true)
 
-            expect(blob.raw_binary?).to be_truthy
+            expect(blob.binary?).to be_truthy
           end
         end
 
@@ -137,7 +137,7 @@ describe Blob do
           it 'return false' do
             blob = fake_blob(path: 'file.md', lfs: true)
 
-            expect(blob.raw_binary?).to be_falsey
+            expect(blob.binary?).to be_falsey
           end
         end
       end
@@ -148,7 +148,7 @@ describe Blob do
             it 'returns false' do
               blob = fake_blob(path: 'file.txt', lfs: true)
 
-              expect(blob.raw_binary?).to be_falsey
+              expect(blob.binary?).to be_falsey
             end
           end
 
@@ -156,7 +156,7 @@ describe Blob do
             it 'returns false' do
               blob = fake_blob(path: 'file.ics', lfs: true)
 
-              expect(blob.raw_binary?).to be_falsey
+              expect(blob.binary?).to be_falsey
             end
           end
         end
@@ -166,7 +166,7 @@ describe Blob do
             it 'returns false' do
               blob = fake_blob(path: 'file.rb', lfs: true)
 
-              expect(blob.raw_binary?).to be_falsey
+              expect(blob.binary?).to be_falsey
             end
           end
 
@@ -174,7 +174,7 @@ describe Blob do
             it 'returns true' do
               blob = fake_blob(path: 'file.exe', lfs: true)
 
-              expect(blob.raw_binary?).to be_truthy
+              expect(blob.binary?).to be_truthy
             end
           end
         end
@@ -184,7 +184,7 @@ describe Blob do
             it 'returns false' do
               blob = fake_blob(path: 'file.ini', lfs: true)
 
-              expect(blob.raw_binary?).to be_falsey
+              expect(blob.binary?).to be_falsey
             end
           end
 
@@ -192,7 +192,7 @@ describe Blob do
             it 'returns true' do
               blob = fake_blob(path: 'file.wtf', lfs: true)
 
-              expect(blob.raw_binary?).to be_truthy
+              expect(blob.binary?).to be_truthy
             end
           end
         end
@@ -204,7 +204,7 @@ describe Blob do
         it 'returns true' do
           blob = fake_blob(path: 'file.pdf', binary: true)
 
-          expect(blob.raw_binary?).to be_truthy
+          expect(blob.binary?).to be_truthy
         end
       end
 
@@ -212,7 +212,7 @@ describe Blob do
         it 'return false' do
           blob = fake_blob(path: 'file.md')
 
-          expect(blob.raw_binary?).to be_falsey
+          expect(blob.binary?).to be_falsey
         end
       end
     end
diff --git a/spec/models/diff_viewer/base_spec.rb b/spec/models/diff_viewer/base_spec.rb
index c90b32c5d77..f4efe5a7b3a 100644
--- a/spec/models/diff_viewer/base_spec.rb
+++ b/spec/models/diff_viewer/base_spec.rb
@@ -58,7 +58,7 @@ describe DiffViewer::Base do
 
       context 'when the binaryness does not match' do
         before do
-          allow_any_instance_of(Blob).to receive(:binary?).and_return(true)
+          allow_any_instance_of(Blob).to receive(:binary_in_repo?).and_return(true)
         end
 
         it 'returns false' do
@@ -141,4 +141,25 @@ describe DiffViewer::Base do
       end
     end
   end
+
+  describe '#render_error_message' do
+    it 'returns nothing when no render_error' do
+      expect(viewer.render_error).to be_nil
+      expect(viewer.render_error_message).to be_nil
+    end
+
+    context 'when render_error error' do
+      before do
+        allow(viewer).to receive(:render_error).and_return(:too_large)
+      end
+
+      it 'returns an error message' do
+        expect(viewer.render_error_message).to include('it is too large')
+      end
+
+      it 'includes a "view the blob" link' do
+        expect(viewer.render_error_message).to include('view the blob')
+      end
+    end
+  end
 end
diff --git a/spec/models/diff_viewer/server_side_spec.rb b/spec/models/diff_viewer/server_side_spec.rb
index 98a8f6d4cc9..86b14b6ebf3 100644
--- a/spec/models/diff_viewer/server_side_spec.rb
+++ b/spec/models/diff_viewer/server_side_spec.rb
@@ -32,4 +32,24 @@ describe DiffViewer::ServerSide do
       end
     end
   end
+
+  describe '#render_error_reason' do
+    context 'when the diff file is stored externally' do
+      before do
+        allow(diff_file).to receive(:stored_externally?).and_return(true)
+      end
+
+      it 'returns error message if stored in LFS' do
+        allow(diff_file).to receive(:external_storage).and_return(:lfs)
+
+        expect(subject.render_error_message).to include('it is stored in LFS')
+      end
+
+      it 'returns error message if stored externally' do
+        allow(diff_file).to receive(:external_storage).and_return(:foo)
+
+        expect(subject.render_error_message).to include('it is stored externally')
+      end
+    end
+  end
 end
diff --git a/spec/support/helpers/fake_blob_helpers.rb b/spec/support/helpers/fake_blob_helpers.rb
index bc9686ed9cf..801ca8b7412 100644
--- a/spec/support/helpers/fake_blob_helpers.rb
+++ b/spec/support/helpers/fake_blob_helpers.rb
@@ -23,7 +23,7 @@ module FakeBlobHelpers
       0
     end
 
-    def binary?
+    def binary_in_repo?
       @binary
     end
 
diff --git a/spec/support/helpers/test_env.rb b/spec/support/helpers/test_env.rb
index d52c40ff4f1..d352a7cdf1a 100644
--- a/spec/support/helpers/test_env.rb
+++ b/spec/support/helpers/test_env.rb
@@ -62,7 +62,8 @@ module TestEnv
     'between-create-delete-modify-move'  => '3f5f443',
     'after-create-delete-modify-move'    => 'ba3faa7',
     'with-codeowners'                    => '219560e',
-    'submodule_inside_folder'            => 'b491b92'
+    'submodule_inside_folder'            => 'b491b92',
+    'png-lfs'                            => 'fe42f41'
   }.freeze
 
   # gitlab-test-fork is a fork of gitlab-fork, but we don't necessarily