chore: Address PR comments

Author: lqiu96

.kokoro/nightly/downstream-protobuf-binary-compatibility.sh

@@ -40,10 +40,8 @@ function build_artifact_list() {
   for artifact_id_prefix in "${!api_maven_mapping[@]}"; do
     group_id="${api_maven_mapping[${artifact_id_prefix}]}"
 
-    # Match all artifacts that start with the $artifact_id_prefix or grpc to exclude any proto modules.
-    # grpc-* module are included as gRPC-Java controls their Protobuf version and may generate code
-    # using a different version of Protobuf
-    repo_artifact_list=$(cat "versions.txt" | grep -E "^(${artifact_id_prefix}|grpc)" || true)
+    # Match all artifacts that start with the $artifact_id_prefix exclude any non-relevant modules.
+    repo_artifact_list=$(cat "versions.txt" | grep -E "^${artifact_id_prefix}" || true)
 
     # Only proceed if there are matching elements
     if [ -n "${repo_artifact_list}" ]; then
@@ -60,6 +58,26 @@ function build_artifact_list() {
         artifact_list="${artifact_list},${repo_artifact_list}"
       fi
     fi
+
+    # grpc-* module are included as gRPC-Java controls their Protobuf version and may generate code
+    # using a different version of Protobuf
+    grpc_repo_artifact_list=$(cat "versions.txt" | grep -E "^grpc" || true)
+
+    # Only proceed if there are matching elements
+    if [ -n "${grpc_repo_artifact_list}" ]; then
+      # Exclude any matches to BOM artifacts or emulators. The repo artifact list will look like:
+      # "com.google.cloud:google-cloud-accessapproval:2.60.0-SNAPSHOT,com.google.cloud:google-cloud-aiplatform:3.60.0-SNAPSHOT,"
+      grpc_repo_artifact_list=$(echo "${grpc_repo_artifact_list}" | awk -F: "{\$1=\"${group_id}:\"\$1; \$2=\"\"; print}" OFS=: | sed 's/::/:/' | tr '\n' ',')
+      # Remove the trailing comma after the last entry
+      grpc_repo_artifact_list=${grpc_repo_artifact_list%,}
+
+      # The first entry added is not separated with a comma. Avoids generating `,{ARTIFACT_LIST}`
+      if [ -z "${artifact_list}" ]; then
+        grpc_artifact_list="${grpc_repo_artifact_list}"
+      else
+        grpc_artifact_list="${grpc_artifact_list},${grpc_repo_artifact_list}"
+      fi
+    fi
   done
 }
 
@@ -78,6 +96,7 @@ for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
   mvn -B -ntp install -T 1C -DskipTests -Dclirr.skip -Denforcer.skip
 
   artifact_list=""
+  grpc_artifact_list=""
   if [ "${repo}" == "google-cloud-java" ]; then
     build_artifact_list monorepo_handwritten_libraries
   else
@@ -89,11 +108,18 @@ for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
 
   echo "Artifact List: ${artifact_list}"
   # Only run Linkage Checker if the repo has any relevant artifacts to test for
-  if [ -n "${artifact_list}" ]; then
+  if [ -n "${artifact_list}" ] && [ -n "${grpc_artifact_list}" ]; then
     # The `-s` argument filters the linkage check problems that stem from the artifact
+    # There are two calls to Linkage Checker: 1. repo's handwritten modules 2. repo's gRPC modules
+    # This is because mvn has a limit on the number of program arguments you can pass in
+
     program_args="-r --artifacts ${artifact_list},com.google.protobuf:protobuf-java:${PROTOBUF_RUNTIME_VERSION},com.google.protobuf:protobuf-java-util:${PROTOBUF_RUNTIME_VERSION} -s ${artifact_list}"
     echo "Linkage Checker Program Arguments: ${program_args}"
     mvn -B -ntp exec:java -Dexec.args="${program_args}" -P exec-linkage-checker
+
+    program_args="-r --artifacts ${artifact_list},com.google.protobuf:protobuf-java:${PROTOBUF_RUNTIME_VERSION},com.google.protobuf:protobuf-java-util:${PROTOBUF_RUNTIME_VERSION} -s ${grpc_artifact_list}"
+    echo "Linkage Checker Program Arguments for gRPC Modules: ${program_args}"
+    mvn -B -ntp exec:java -Dexec.args="${program_args}" -P exec-linkage-checker
   else
     echo "Unable to find any matching artifacts to test in ${repo}"
     exit 1