don't preload sourcemaps

closes CFA-48

Change-Id: I38818cd14e681188663e74251658788054d1158e
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/339163
Reviewed-by: James Butters <jbutters@instructure.com>
Reviewed-by: Keith Garner <kgarner@instructure.com>
QA-Review: Aaron Shafovaloff <ashafovaloff@instructure.com>
Product-Review: Aaron Shafovaloff <ashafovaloff@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>

lib/canvas/cdn/registry/webpack.rb

@@ -48,7 +48,8 @@ module Canvas
         end
 
         def entries
-          @manifest.values.grep(/-entry-\w+\.js/).map { |file_path| realpath(file_path) }
+          # contains -entry- in filename, ends in .js, but doesn't end in .map.js
+          @manifest.values.grep(/-entry-\w+(?<!\.map)\.js/).map { |file_path| realpath(file_path) }
         end
 
         private

spec/lib/canvas/cdn/registry_spec.rb

@@ -104,5 +104,15 @@ describe Canvas::Cdn::Registry do
         ]
       )
     end
+
+    it "does not include .map.js files" do
+      @webpack_manifest = { "main" => "a-entry-1234.js", "foo" => "a-entry-1234.map.js" }
+
+      expect(subject.entries).to eq(
+        [
+          "/dist/webpack-dev/a-entry-1234.js"
+        ]
+      )
+    end
   end
 end