feat: Add canonical=false option to disable canonical URL output (#521)

Merge pull request 521

Author: rathboma

docs/advanced-usage.md

@@ -12,6 +12,18 @@ If for some reason, you don't want the plugin to output `<title>` tags on each p
 ```
 <!-- {% endraw %} -->
 
+### Disabling `<link rel="canonical">` output
+
+If you're using another plugin to generate canonical URLs (such as [jekyll-polyglot](https://github.com/untra/polyglot) for multilingual sites), you can disable the canonical URL output:
+
+<!-- {% raw %} -->
+```
+{% seo canonical=false %}
+```
+<!-- {% endraw %} -->
+
+This will prevent the plugin from outputting the `<link rel="canonical">` tag, while still outputting all other SEO tags including the `<meta property="og:url">` tag.
+
 ### Author information
 
 Author information is used to propagate the `creator` field of Twitter summary cards. This should be an author-specific, not site-wide Twitter handle (the site-wide username be stored as `site.twitter.username`).

lib/jekyll-seo-tag/drop.rb

@@ -33,6 +33,13 @@ def title?
         @display_title = (@text !~ %r!title=false!i)
       end
 
+      # Should the `<link rel="canonical">` tag be generated for this page?
+      def canonical?
+        return @canonical if defined?(@canonical)
+
+        @canonical = (@text !~ %r!canonical=false!i)
+      end
+
       def site_title
         @site_title ||= format_string(site["title"] || site["name"])
       end

lib/template.html

@@ -21,8 +21,8 @@
 {% endif %}
 
 {% if site.url %}
-  <link rel="canonical" href="{{ seo_tag.canonical_url }}" />
-  <meta property="og:url" content="{{ seo_tag.canonical_url }}" />
+  {% if seo_tag.canonical? %}<link rel="canonical" href="{{ seo_tag.canonical_url }}" />
+  {% endif %}<meta property="og:url" content="{{ seo_tag.canonical_url }}" />
 {% endif %}
 
 {% if seo_tag.site_title %}

spec/jekyll_seo_tag/drop_spec.rb

@@ -535,6 +535,28 @@
     end
   end
 
+  context "canonical?" do
+    it "knows to include the canonical by default" do
+      expect(subject.canonical?).to be_truthy
+    end
+
+    context "with canonical=false" do
+      let(:text) { "canonical=false" }
+
+      it "knows not to include the canonical" do
+        expect(subject.canonical?).to be_falsy
+      end
+    end
+
+    context "with CANONICAL=FALSE (case insensitive)" do
+      let(:text) { "CANONICAL=FALSE" }
+
+      it "knows not to include the canonical" do
+        expect(subject.canonical?).to be_falsy
+      end
+    end
+  end
+
   context "pagination" do
     let(:context) do
       make_context(

spec/jekyll_seo_tag_integration_spec.rb

@@ -622,6 +622,19 @@
     end
   end
 
+  context "with canonical=false" do
+    let(:site) { make_site("url" => "http://example.invalid") }
+    let(:text) { "canonical=false" }
+
+    it "does not output a canonical link tag" do
+      expect(output).not_to match(%r!<link rel="canonical"!)
+    end
+
+    it "still outputs og:url meta tag" do
+      expect(output).to match(%r!<meta property="og:url"!)
+    end
+  end
+
   context "with pagination" do
     let(:context) { make_context({}, "paginator" => paginator) }