Fixing SyncTeX errors in Server Pro 2.0.0 and 2.0.1

Unfortunately Server Pro in its versions 2.0.0 and 2.0.1 has been released with a problem with SyncTeX functionality, causing the server to return a 400 error every time we try to sync the position between a document and the generated pdf.

This problem is present only when using Sandboxed Compiles.

It's possible to fix the issue with a workaround that involves:

1. The addition of a new environment variable to sharelatex container in docker-compose.yml
2. Executing a command after sharelatex container has been initiated.

Step 1: adding SYNCTEX_BIN_HOST_PATH to docker-compose.yml

We need to add a new SYNCTEX_BIN_HOST_PATH, pointing to a synctex executable in the same host directory mounted as /var/lib/sharelatex inside the container. This means that if the volume is mounted as:

volumes:
  - /var/sharelatex_data:/var/lib/sharelatex

Then the new environment variable should be:

SYNCTEX_BIN_HOST_PATH: "/var/sharelatex_data/synctex"

Step 2: executing a command inside sharelatex container

Once we've restarted the sharelatex container after adding the environment variable we need to execute the following command:

docker exec sharelatex cp /var/www/sharelatex/clsi/bin/synctex /var/lib/sharelatex/synctex 

Once that's done, we should start seeing 200 responses when syncing the position between document and pdf.

Executing again this command shouldn't be required after a service restart.