HBASE-26871 shaded mapreduce and shaded byo-hadoop client artifacts contain no classes (#4279)

- add a test to the shaded artifact validation that checks for java classes

Signed-off-by: Andrew Purtell <apurtell@apache.org>

hbase-shaded/hbase-shaded-check-invariants/src/test/resources/ensure-jars-have-correct-contents.sh

@@ -114,6 +114,10 @@ declare -i bad_artifacts=0
 declare -a bad_contents
 for artifact in "${artifact_list[@]}"; do
   bad_contents=($(jar tf "${artifact}" | grep -v -E "${allowed_expr}" || true))
+  class_count=$(jar tf "${artifact}" | grep -c -E '\.class$' || true)
+  if [ ${#bad_contents[@]} -eq 0 ] && [ "${class_count}" -lt 1 ]; then
+    bad_contents=("The artifact contains no java class files.")
+  fi
   if [ ${#bad_contents[@]} -gt 0 ]; then
     echo "[ERROR] Found artifact with unexpected contents: '${artifact}'"
     echo "    Please check the following and either correct the build or update"

hbase-shaded/hbase-shaded-with-hadoop-check-invariants/src/test/resources/ensure-jars-have-correct-contents.sh

@@ -114,6 +114,10 @@ declare -i bad_artifacts=0
 declare -a bad_contents
 for artifact in "${artifact_list[@]}"; do
   bad_contents=($(jar tf "${artifact}" | grep -v -E "${allowed_expr}" || true))
+  class_count=$(jar tf "${artifact}" | grep -c -E '\.class$' || true)
+  if [ ${#bad_contents[@]} -eq 0 ] && [ "${class_count}" -lt 1 ]; then
+    bad_contents=("The artifact contains no java class files.")
+  fi
   if [ ${#bad_contents[@]} -gt 0 ]; then
     echo "[ERROR] Found artifact with unexpected contents: '${artifact}'"
     echo "    Please check the following and either correct the build or update"