use liquid builtin variable resolution

features/citation.feature

@@ -242,3 +242,38 @@ Feature: Citations
     Then the _site directory should exist
     And the "_site/scholar.html" file should exist
     And I should see "Flanagan" in "_site/scholar.html"
+
+  @tags @cite @variables @data
+  Scenario: A Simple Citation using liquid variables
+    Given I have a scholar configuration with:
+      | key          | value             |
+      | source       | ./_bibliography   |
+      | bibliography | my_references     |
+    And I have a "_bibliography" directory
+    And I have a file "_bibliography/my_references.bib":
+      """
+      @book{ruby,
+        title     = {The Ruby Programming Language},
+        author    = {Flanagan, David and Matsumoto, Yukihiro},
+        year      = {2008},
+        publisher = {O'Reilly Media}
+      }
+      """
+    And I have a "_data" directory
+    And I have a file "_data/covers.yml":
+      """
+      - reference: "ruby"
+        image: "/img/covers/cover_01.png"
+      """
+    And I have a page "scholar.html":
+      """
+      ---
+      ---
+      {% for cover in site.data.covers %}
+        {% cite cover.reference %}
+      {% endfor %}
+      """
+    When I run jekyll
+    Then the _site directory should exist
+    And the "_site/scholar.html" file should exist
+    And I should see "Flanagan" in "_site/scholar.html"

lib/jekyll/scholar/utilities.rb

@@ -376,6 +376,13 @@ module Jekyll
       def set_context_to(context)
         @context, @site, = context, context.registers[:site]
         config.merge!(site.config['scholar'] || {})
+
+        # De-reference keys
+        keys.map! do |key|
+          context.send(:resolve, key) || key
+        end unless keys.nil?
+
+        self
       end
     end