Add option to validate links

README.md

@@ -61,6 +61,7 @@ You can configure this plugin in `_config.yml` under the `relative_links` key. T
 relative_links:
   enabled:     true
   collections: false
+  validate_links: false
 ```
 
 ### Excluding files
@@ -104,3 +105,14 @@ File | Link
 ### Disabling
 
 Even if the plugin is enabled (e.g., via the `:jekyll_plugins` group in your Gemfile) you can disable it by setting the `enabled` key to `false`.
+
+### Validating Links
+
+By default, the plugin doesn't validate if linked files exist. It will silently keep the original Markdown links when the target file doesn't exist.
+
+Setting the `validate_links` option to `true` enables link validation, causing Jekyll to raise an error when attempting to link to a nonexistent file, similar to Jekyll's native `{% link %}` tag.
+
+```yml
+relative_links:
+  validate_links: true
+```

lib/jekyll-relative-links/generator.rb

@@ -18,6 +18,7 @@ class Generator < Jekyll::Generator
     CONFIG_KEY = "relative_links"
     ENABLED_KEY = "enabled"
     COLLECTIONS_KEY = "collections"
+    VALIDATE_LINKS_KEY = "validate_links"
     LOG_KEY = "Relative Links:"
 
     safe true
@@ -45,6 +46,7 @@ def generate(site)
       end
     end
 
+    # rubocop:disable Metrics/AbcSize
     def replace_relative_links!(document)
       url_base = File.dirname(document.relative_path)
       return document if document.content.nil?
@@ -55,6 +57,12 @@ def replace_relative_links!(document)
 
         path = path_from_root(link.path, url_base)
         url  = url_for_path(path)
+
+        if url.nil? && validate_links?
+          source = document.relative_path
+          raise "Invalid reference to '#{link.path}' in '#{source}'"
+        end
+
         next original unless url
 
         link.path = url
@@ -65,6 +73,7 @@ def replace_relative_links!(document)
     rescue ArgumentError => e
       raise e unless e.to_s.start_with?("invalid byte sequence in UTF-8")
     end
+    # rubocop:enable Metrics/AbcSize
 
     private
 
@@ -151,6 +160,10 @@ def collections?
       option(COLLECTIONS_KEY) == true
     end
 
+    def validate_links?
+      option(VALIDATE_LINKS_KEY) == true
+    end
+
     def excluded?(document)
       return false unless option("exclude")
 

spec/jekyll-relative-links/generator_spec.rb

@@ -340,6 +340,43 @@
     end
   end
 
+  context "link validation" do
+    it "knows when validation is enabled" do
+      plugin_config = { "validate_links" => true }
+      generator = described_class.new({ "relative_links" => plugin_config })
+      expect(generator.send(:validate_links?)).to be true
+    end
+
+    it "knows when validation is disabled" do
+      plugin_config = { "validate_links" => false }
+      generator = described_class.new({ "relative_links" => plugin_config })
+      expect(generator.send(:validate_links?)).to be false
+    end
+
+    it "has validation disabled by default" do
+      generator = described_class.new({})
+      expect(generator.send(:validate_links?)).to be false
+    end
+
+    context "when validation is enabled" do
+      let(:plugin_config) { { "validate_links" => true } }
+
+      before do
+        site.reset
+        site.read
+        subject.instance_variable_set :@site, site
+      end
+
+      it "raises an error when a file doesn't exist" do
+        page.content = "[Missing](./nonexistent.md)"
+
+        expect do
+          subject.replace_relative_links!(page)
+        end.to raise_error(%r!Invalid reference to './nonexistent.md' in 'page.md'!)
+      end
+    end
+  end
+
   context "a page without content" do
     before { page_by_path(site, "page.md").content = nil }