EvaluatedDocument.toInputStream usage may result in corrupt documents

[mbali]

The EvaluatedDocument.toInputStream function's default implementation uses a PipedInputStream/PipedOutputStream pair, and writes into the output stream in an executor thread. If this write results in an error, the thread reading the input stream will not get notified of the problem, and reads an unfinished and probably corrupt document.

[erdos]

Hey, this is a good catch.

Temporary solution is to use EvaluatedDocument.writeToStream(OutputStream outputStream) to render the document.

I will take a look at how we could change toInputStream to propagate any errors that happens during the rendering.
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