Set og:image:alt OpenGraph property

app/controllers/diary_entries_controller.rb

@@ -69,6 +69,7 @@ class DiaryEntriesController < ApplicationController
     if @entry
       @title = t ".title", :user => params[:display_name], :title => @entry.title
       @og_image = @entry.body.image
+      @og_image_alt = @entry.body.image_alt
       @comments = can?(:unhide, DiaryComment) ? @entry.comments : @entry.visible_comments
     else
       @title = t "diary_entries.no_such_entry.title", :id => params[:id]

app/helpers/open_graph_helper.rb

@@ -1,15 +1,16 @@
 module OpenGraphHelper
   require "addressable/uri"
 
-  def opengraph_tags(title = nil, og_image = nil)
+  def opengraph_tags(title = nil, og_image = nil, og_image_alt = nil)
     tags = {
       "og:site_name" => t("layouts.project_name.title"),
       "og:title" => title || t("layouts.project_name.title"),
       "og:type" => "website",
-      "og:image" => og_image_url(og_image),
       "og:url" => url_for(:only_path => false),
       "og:description" => t("layouts.intro_text")
-    }
+    }.merge(
+      opengraph_image_properties(og_image, og_image_alt)
+    )
 
     safe_join(tags.map do |property, content|
       tag.meta(:property => property, :content => content)
@@ -18,12 +19,20 @@ module OpenGraphHelper
 
   private
 
-  def og_image_url(og_image)
+  def opengraph_image_properties(og_image, og_image_alt)
     begin
-      return Addressable::URI.join(root_url, og_image).normalize if og_image
+      if og_image
+        properties = {}
+        properties["og:image"] = Addressable::URI.join(root_url, og_image).normalize
+        properties["og:image:alt"] = og_image_alt if og_image_alt
+        return properties
+      end
     rescue Addressable::URI::InvalidURIError
       # return default image
     end
-    image_url("osm_logo_256.png")
+    {
+      "og:image" => image_url("osm_logo_256.png"),
+      "og:image:alt" => t("layouts.logo.alt_text")
+    }
   end
 end

app/views/layouts/_meta.html.erb

@@ -21,7 +21,7 @@
 <% end -%>
 <%= tag.link :rel => "search", :type => "application/opensearchdescription+xml", :title => "OpenStreetMap Search", :href => asset_path("osm.xml") %>
 <%= tag.meta :name => "description", :content => "OpenStreetMap is the free wiki world map." %>
-<%= opengraph_tags(@title, @og_image) %>
+<%= opengraph_tags(@title, @og_image, @og_image_alt) %>
 <% if flash[:matomo_goal] -%>
 <%= tag.meta :name => "matomo-goal", :content => flash[:matomo_goal] %>
 <% end -%>

test/controllers/diary_entries_controller_test.rb

@@ -657,6 +657,9 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", ActionController::Base.helpers.image_url("osm_logo_256.png", :host => root_url)
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "OpenStreetMap logo"
+    end
   end
 
   def test_show_og_image
@@ -668,6 +671,9 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", "https://example.com/picture.jpg"
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "some picture"
+    end
   end
 
   def test_show_og_image_with_relative_uri
@@ -679,6 +685,9 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", "#{root_url}picture.jpg"
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "some local picture"
+    end
   end
 
   def test_show_og_image_with_spaces
@@ -690,6 +699,9 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", "https://example.com/the%20picture.jpg"
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "some picture"
+    end
   end
 
   def test_show_og_image_with_relative_uri_and_spaces
@@ -701,6 +713,9 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", "#{root_url}the%20picture.jpg"
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "some local picture"
+    end
   end
 
   def test_show_og_image_with_invalid_uri
@@ -712,6 +727,21 @@ class DiaryEntriesControllerTest < ActionDispatch::IntegrationTest
     assert_dom "head meta[property='og:image']" do
       assert_dom "> @content", ActionController::Base.helpers.image_url("osm_logo_256.png", :host => root_url)
     end
+    assert_dom "head meta[property='og:image:alt']" do
+      assert_dom "> @content", "OpenStreetMap logo"
+    end
+  end
+
+  def test_show_og_image_without_alt
+    user = create(:user)
+    diary_entry = create(:diary_entry, :user => user, :body => "<img src='https://example.com/no_alt.gif'>")
+
+    get diary_entry_path(user, diary_entry)
+    assert_response :success
+    assert_dom "head meta[property='og:image']" do
+      assert_dom "> @content", "https://example.com/no_alt.gif"
+    end
+    assert_dom "head meta[property='og:image:alt']", :count => 0
   end
 
   def test_hide