Load Jekyll plugins from BUNDLE_GEMFILE location (#8585)

Merge pull request 8585

lib/jekyll/plugin_manager.rb

@@ -46,7 +46,7 @@ module Jekyll
     end
 
     def self.require_from_bundler
-      if !ENV["JEKYLL_NO_BUNDLER_REQUIRE"] && File.file?("Gemfile")
+      if !ENV["JEKYLL_NO_BUNDLER_REQUIRE"] && gemfile_exists?
         require "bundler"
 
         Bundler.setup
@@ -61,6 +61,13 @@ module Jekyll
       end
     end
 
+    # Check for the existence of a Gemfile.
+    #
+    # Returns true if a Gemfile exists in the places bundler will look
+    def self.gemfile_exists?
+      File.file?("Gemfile") || (ENV["BUNDLE_GEMFILE"] && File.file?(ENV["BUNDLE_GEMFILE"]))
+    end
+
     # Check whether a gem plugin is allowed to be used during this build.
     #
     # plugin_name - the name of the plugin

test/test_plugin_manager.rb

@@ -10,6 +10,13 @@ class TestPluginManager < JekyllUnitTest
     FileUtils.mv "Gemfile.old", "Gemfile"
   end
 
+  def with_bundle_gemfile
+    FileUtils.mv "Gemfile", "AlternateGemfile"
+    yield
+  ensure
+    FileUtils.mv "AlternateGemfile", "Gemfile"
+  end
+
   context "JEKYLL_NO_BUNDLER_REQUIRE set to `nil`" do
     should "require from bundler" do
       with_env("JEKYLL_NO_BUNDLER_REQUIRE", nil) do
@@ -20,6 +27,18 @@ class TestPluginManager < JekyllUnitTest
     end
   end
 
+  context "BUNDLE_GEMFILE set to `AlternateGemfile`" do
+    should "require from bundler" do
+      with_env("BUNDLE_GEMFILE", "AlternateGemfile") do
+        with_bundle_gemfile do
+          assert Jekyll::PluginManager.require_from_bundler,
+                 "require_from_bundler should return true"
+          assert ENV["JEKYLL_NO_BUNDLER_REQUIRE"], "Gemfile plugins were not required."
+        end
+      end
+    end
+  end
+
   context "JEKYLL_NO_BUNDLER_REQUIRE set to `true`" do
     should "not require from bundler" do
       with_env("JEKYLL_NO_BUNDLER_REQUIRE", "true") do