Implement mechanism to serve files via custom protocols

[hmil]

In some scenarios, one may need the runtime files to be served over http:// instead of file:// (ie. to bypass cross origin request security).

In this first attempt, I created a new trait for file materializer which also provide an absolute access url for materialized files. This allows to encapsulate the "absolutePath" function together with the materializer. This trait has two direct implementations. One which is a refactoring of the current code (for the scenario where you don't care how selenium gets its runtime files, you just want it to work). The other one allows to customize the location where files get saved and the actual URL used by selenium to access them.

At usage it is pretty nice:

jsSettings(
  jsEnv := new SeleniumJSEnv(org.scalajs.jsenv.selenium.Firefox)
      // materializes files in the .tmp directory which is served over http by an external program
      .withMaterializer(new SpecificFileMaterializer(".tmp", "http://localhost:8080"))
)

The main problem I see with this approach is that my FileMaterializer trait is pretty redundant with respect to the VirtualFileMaterializer class. I suppose a cleaner approach would be to push all of this logic upstream such that VirtualFileMaterializer is the trait with two children and it exposes the getAbsolutePath method.

[nicolasstucki]

You will need to add some tests that can be run on the CI.

[nicolasstucki]

This comment should be formatted as follows.

/** Materializes virtual files in a temporary directory and links to them
 *  via file://
 */

[nicolasstucki]

The code logic looks good to me, but we really need to test it on the CI.
That's all.

[hmil]

Not sure how to test the feature exactly. I added a new target seleniumJSHttpEnv using the SpecificFileMaterializer and running one test which makes sure the script is served over HTTP.
I also added a python command to serve the files over http on travis.

I noticed there is no '.idea/' in the .gitignore, shall this be added ?

[sjrd]

I noticed there is no '.idea/' in the .gitignore, shall this be added ?

No. You should add that to your global .gitignore file, so that it applies only on machine, but to all your projects.

[sjrd]

I think, but needs verification, that it would be better if this method returned a URL, and getAbsolutePath was removed.

[nicolasstucki]

You should add fullOpt to the tests:

- sbt ++$TRAVIS_SCALA_VERSION seleniumJSHttpEnvTest/test 'set scalaJSStage in Global := FullOptStage' seleniumJSHttpEnvTest/test

[nicolasstucki]

That is all.

[nicolasstucki]

Could you also change the commit message to Fix #22: Implement mechanism to serve files via custom protocols. with no additional description.

[hmil]

All done, thanks for the review.

[nicolasstucki]

LGTM