feat(docker): Add build var for optionally installing abiword (#4796)

This MR introduces a docker build variable `INSTALL_ABIWORD`. When set
to any value other than `0`, ABIWORD is installed in the resulting
docker container, enabling the possibility to configure ABIWORD in
settings.json.docker or via ENV VAR `ABIWORD` for exporting to
DOC/PDF/ODT.

Documentation is included inline and in the docker markdown file.

Dockerfile

@@ -15,6 +15,22 @@ LABEL maintainer="Etherpad team, https://github.com/ether/etherpad-lite"
 #   ETHERPAD_PLUGINS="ep_codepad ep_author_neat"
 ARG ETHERPAD_PLUGINS=
 
+# Control whether abiword will be installed, enabling exports to DOC/PDF/ODT formats.
+# By default, it is not installed.
+# If given any value, abiword will be installed.
+#
+# EXAMPLE:
+#   INSTALL_ABIWORD=true
+ARG INSTALL_ABIWORD=
+
+# Control whether libreoffice will be installed, enabling exports to DOC/PDF/ODT formats.
+# By default, it is not installed.
+# If given any value, libreoffice will be installed.
+#
+# EXAMPLE:
+#   INSTALL_LIBREOFFICE=true
+ARG INSTALL_SOFFICE=
+
 # By default, Etherpad container is built and run in "production" mode. This is
 # leaner (development dependencies are not installed) and runs faster (among
 # other things, assets are minified & compressed).
@@ -28,6 +44,13 @@ RUN useradd --uid 5001 --create-home etherpad
 
 RUN mkdir /opt/etherpad-lite && chown etherpad:0 /opt/etherpad-lite
 
+# install abiword for DOC/PDF/ODT export
+RUN [ -z "${INSTALL_ABIWORD}" ] || (apt update && apt -y install abiword && apt clean && rm -rf /var/lib/apt/lists/*)
+
+# install libreoffice for DOC/PDF/ODT export
+# the mkdir is needed for configuration of openjdk-11-jre-headless, see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=863199
+RUN [ -z "${INSTALL_SOFFICE}" ] || (apt update && mkdir -p /usr/share/man/man1 && apt -y install libreoffice && apt clean && rm -rf /var/lib/apt/lists/*)
+
 USER etherpad
 
 WORKDIR /opt/etherpad-lite

doc/docker.md

@@ -29,6 +29,30 @@ The variable value has to be a space separated, double quoted list of plugin nam
 
 Some plugins will need personalized settings. Just refer to the previous section, and include them in your custom `settings.json.docker`.
 
+### Rebuilding including export functionality for DOC/PDF/ODT
+
+If you want to be able to export your pads to DOC/PDF/ODT files, you can install
+either Abiword or Libreoffice via setting a build variable.
+
+#### Via Abiword
+
+For installing Abiword, set the `INSTALL_ABIWORD` build variable to any value.
+
+Also, you will need to configure the path to the abiword executable
+via setting the `abiword` property in `<BASEDIR>/settings.json.docker` to 
+`/usr/bin/abiword` or via setting the environment variable  `ABIWORD` to 
+`/usr/bin/abiword`.
+
+#### Via Libreoffice
+
+For installing Libreoffice instead, set the `INSTALL_SOFFICE` build variable
+to any value.
+
+Also, you will need to configure the path to the libreoffice executable
+via setting the `soffice` property in `<BASEDIR>/settings.json.docker` to 
+`/usr/bin/soffice` or via setting the environment variable  `SOFFICE` to 
+`/usr/bin/soffice`.
+
 ### Examples
 
 Build a Docker image from the currently checked-out code: