Test for #141

When mutating objects from the cache, sometimes those objects are placed back into the cache leading to accidental absolute paths.

This commit verifies that no absolute paths are accidentally stored in the cache.

test/test_caching.rb

@@ -427,6 +427,41 @@ def teardown
     end
   end
 
+  test "history cache is not poluted" do
+    dependency_file = File.join(fixture_path('asset'), "dependencies", "a.js")
+    env1 = Sprockets::Environment.new(fixture_path('asset')) do |env|
+      env.append_path(".")
+      env.cache = @cache
+    end
+    env1['required_assets.js']
+
+    sandbox dependency_file do
+      write(dependency_file, "var aa = 2;")
+      env1['required_assets.js']
+
+      # We must use private APIs to test this behavior
+      # https://github.com/rails/sprockets/pull/141
+      cache_entries = @cache.send(:find_caches).map do |file, _|
+        key    = file.gsub(/\.cache\z/, ''.freeze).split(@cache_dir).last
+        result = @cache.get(key)
+
+        if result.is_a?(Array)
+          result if result.first.is_a?(Set)
+        else
+          nil
+        end
+      end.compact
+
+      assert cache_entries.any?
+
+      cache_entries.each do |sets|
+        sets.each do |set|
+          refute set.any? {|uri| uri.include?(env1.root) }, "Expected entry in cache to not include absolute paths but did: #{set.inspect}"
+        end
+      end
+    end
+  end
+
   test "no absolute paths are retuned from cache" do
     env1 = Sprockets::Environment.new(fixture_path('default')) do |env|
       env.append_path(".")