test: Improve debugging ability for docker tests

The script in packager/testing/dockers/test_dockers.sh now outputs
more useful info for debugging, uses unique container names per OS so
that the containers can be debugged, and allows filtering to re-run
specific OSes if a build fails.

Change-Id: I0cace282549c093a643009f5e60e7545a039168c

packager/testing/dockers/test_dockers.sh

@@ -1,18 +1,66 @@
 #!/bin/bash
 
+# Exit on first error.
 set -e
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 PACKAGER_DIR="$(dirname "$(dirname "$(dirname "$(dirname ${SCRIPT_DIR})")")")"
 
 function docker_run() {
-  docker run -v ${PACKAGER_DIR}:/shaka-packager -w /shaka-packager/src my_container "$@"
+  docker run -v ${PACKAGER_DIR}:/shaka-packager -w /shaka-packager/src ${CONTAINER} "$@"
 }
 
-for docker_file in ${SCRIPT_DIR}/*_Dockerfile ; do
+# Command line arguments will be taken as an allowlist of OSes to run.
-  docker build -t my_container -f ${docker_file} ${SCRIPT_DIR}
+# By default, a regex that matches everything.
+FILTER=".*"
+if [[ $# != 0 ]]; then
+  # Join arguments with a pipe, to make a regex alternation to match any of
+  # them.  The syntax is a mess, but that's bash.  Set IFS (the separator
+  # variable) in a subshell and print the array.  This has the effect of joining
+  # them by the character in IFS. Then add parentheses to make a complete regex
+  # to match all the arguments.
+  FILTER=$(IFS="|"; echo "$*")
+  FILTER="($FILTER)"
+fi
+
+# On exit, print the name of the OS we were on.  This helps identify what to
+# debug when the start of a test run scrolls off-screen.
+trap 'echo "Failed on $OS_NAME!"' exit
+
+echo "Using OS filter: $FILTER"
+RAN_SOMETHING=0
+for DOCKER_FILE in ${SCRIPT_DIR}/*_Dockerfile ; do
+  # Take the basename of the dockerfile path, then remove the trailing
+  # "_Dockerfile" from the file name.  This is the OS name.
+  OS_NAME="$( basename "$DOCKER_FILE" | sed -e 's/_Dockerfile//' )"
+
+  if echo "$OS_NAME" | grep -Eqi "$FILTER"; then
+     echo "Testing $OS_NAME."
+     # Fall through.
+  else
+     echo "Skipping $OS_NAME."
+     continue
+  fi
+
+  # Build a unique container name per OS for debugging purposes and to improve
+  # caching.  Containers names must be in lowercase.
+  # To debug a failure in Alpine, for example, use:
+  #   docker run -it -v /path/to/packager:/shaka-packager \
+  #       packager_test_alpine:latest /bin/bash
+  CONTAINER="$( echo "packager_test_${OS_NAME}" | tr A-Z a-z )"
+
+  RAN_SOMETHING=1
+  docker build -t ${CONTAINER} -f ${DOCKER_FILE} ${SCRIPT_DIR}
   docker_run rm -rf out/Release
   docker_run gclient runhooks
   docker_run ninja -C out/Release
   docker_run out/Release/packager_test.py -v
 done
+
+# Clear the exit trap from above.
+trap - exit
+
+if [[ "$RAN_SOMETHING" == "0" ]]; then
+  echo "No tests were run!  The filter $FILTER did not match any OSes." 1>&2
+  exit 1
+fi