CI: build javadoc in gitlab ci

.gitlab-ci.yml

@@ -60,6 +60,42 @@ test:ant:
         - merge_requests
         - tags
 
+test:javadoc:
+    stage: test
+    image: debian:unstable-slim
+    variables:
+        SCALA: https://downloads.lightbend.com/scala/2.12.13/scala-2.12.13.deb
+        LIBPREFIX: /usr/share/scala/lib
+        LIB_SCALATEST: https://repo1.maven.org/maven2/org/scalatest/scalatest_2.12/3.0.4/scalatest_2.12-3.0.4.jar
+        LIB_SCALACTIC: https://repo1.maven.org/maven2/org/scalactic/scalactic_2.12/3.0.4/scalactic_2.12-3.0.4.jar
+    before_script:
+        # Fix bug installing openjdk-11-jdk-headless's manuals
+        - mkdir -p /usr/share/man/man1/
+        - apt-get update -q
+        - apt-get install -y wget gettext
+            ant openjdk-21-jdk-headless
+            libmockito-java libhamcrest-java junit4
+        # Install specific version of scala
+        - wget -qO scala.deb "${SCALA}"
+        - dpkg -i scala.deb
+        # link to the scala libs with the name `ant test` expects
+        - ln -s "${LIBPREFIX}/scala-xml_2.12-1.0.6.jar" "${LIBPREFIX}/scala-xml.jar"
+        # Download required scala libs
+        - wget -qO "${LIBPREFIX}/scalactic.jar" "${LIB_SCALACTIC}"
+        - wget -qO "${LIBPREFIX}/scalatest.jar" "${LIB_SCALATEST}"
+        # Point ant to the right directories
+        - echo scalatest.libs=/usr/share/scala/lib > override.properties
+        - echo junit.home=/usr/share/java >> override.properties
+        - echo hamcrest.home=/usr/share/java >> override.properties
+        - echo mockito.home=/usr/share/java >> override.properties
+        - echo build.built-by=GitHub Actions >> override.properties
+    script:
+        - ant javadoc
+    only:
+        - master
+        - merge_requests
+        - tags
+
 # Make sure we can build a docker image
 # It's cached for later jobs
 build_docker: