Detect .js files with source maps as generated (#2984)

* Fix .min.js test

* Detect .js files with source maps as generated

lib/linguist/generated.rb

@@ -59,6 +59,7 @@ module Linguist
       godeps? ||
       generated_by_zephir? ||
       minified_files? ||
+      has_source_map? ||
       source_map? ||
       compiled_coffeescript? ||
       generated_parser? ||
@@ -104,6 +105,21 @@ module Linguist
       end
     end
 
+    # Internal: Does the blob contain a source map reference?
+    #
+    # We assume that if one of the last 2 lines starts with a source map
+    # reference, then the current file was generated from other files.
+    # 
+    # We use the last 2 lines because the last line might be empty.
+    # 
+    # We only handle JavaScript, no CSS support yet.
+    # 
+    # Returns true or false.
+    def has_source_map?
+      return false unless extname.downcase == '.js'
+      lines.last(2).any? { |line| line.start_with?('//# sourceMappingURL') }
+    end
+
     # Internal: Is the blob a generated source map?
     #
     # Source Maps usually have .css.map or .js.map extensions. In case they

test/test_generated.rb

@@ -17,6 +17,7 @@ class TestGenerated < Minitest::Test
     assert_raises(DataLoadedError, "Data wasn't loaded when calling generated? on #{blob}") do
       Generated.generated?(blob, lambda { raise DataLoadedError.new })
     end
+    assert Generated.generated?(blob, lambda { IO.read(blob) }), "#{blob} was not recognized as a generated file"
   end
 
   def generated_fixture_without_loading_data(name)
@@ -62,6 +63,9 @@ class TestGenerated < Minitest::Test
     # Minified files
     generated_sample_loading_data("JavaScript/jquery-1.6.1.min.js")
 
+    # JS files with source map reference
+    generated_sample_loading_data("JavaScript/namespace.js")
+
     # Source Map
     generated_fixture_without_loading_data("Data/bootstrap.css.map")
     generated_fixture_loading_data("Data/sourcemap.v3.map")