Fix module env var definition from changeset (#39611)

Updated MODULE env var definition script to match logic performed on Jenkins

.buildkite/scripts/changesets.sh

@@ -1,77 +1,66 @@
 #!/usr/bin/env bash
-
 # This script contains helper functions related to what should be run depending on Git changes
 
+set -euo pipefail
+
 OSS_MODULE_PATTERN="^[a-z0-9]+beat\\/module\\/([^\\/]+)\\/.*"
 XPACK_MODULE_PATTERN="^x-pack\\/[a-z0-9]+beat\\/module\\/([^\\/]+)\\/.*"
 
-are_paths_changed() {
-  local patterns=("${@}")
-  local changelist=()
-  for pattern in "${patterns[@]}"; do
-    changed_files=($(git diff --name-only HEAD@{1} HEAD | grep -E "$pattern"))
-    if [ "${#changed_files[@]}" -gt 0 ]; then
-      changelist+=("${changed_files[@]}")
-    fi
-  done
+definePattern() {
+  pattern="${OSS_MODULE_PATTERN}"
 
-  if [ "${#changelist[@]}" -gt 0 ]; then
-    echo "Files changed:"
-    echo "${changelist[*]}"
-    return 0
-  else
-    echo "No files changed within specified changeset:"
-    echo "${patterns[*]}"
-    return 1
+  if [[ "$beatPath" == *"x-pack/"* ]]; then
+    pattern="${XPACK_MODULE_PATTERN}"
   fi
 }
 
-are_changed_only_paths() {
-  local patterns=("${@}")
-  local changed_files=($(git diff --name-only HEAD@{1} HEAD))
-  local matched_files=()
-  for pattern in "${patterns[@]}"; do
-    local matched=($(grep -E "${pattern}" <<< "${changed_files[@]}"))
-    if [ "${#matched[@]}" -gt 0 ]; then
-      matched_files+=("${matched[@]}")
-    fi
-  done
-  if [ "${#matched_files[@]}" -eq "${#changed_files[@]}" ] || [ "${#changed_files[@]}" -eq 0 ]; then
-    return 0
-  fi
-  return 1
+defineExclusions() {
+  exclude="^$beatPath\/module\/(.*(?<!\.asciidoc|\.png))$"
 }
 
-defineModuleFromTheChangeSet() {
-  # This function sets a `MODULE` env var, required by IT tests, containing a comma separated list of modules for a given beats project (specified via the first argument).
-  # The list is built depending on directories that have changed under `modules/` excluding anything else such as asciidoc and png files.
-  # `MODULE` will empty if no changes apply.
-  local project_path=$1
-  local project_path_transformed=$(echo "$project_path" | sed 's/\//\\\//g')
-  local project_path_exclussion="((?!^${project_path_transformed}\\/).)*\$"
-  local exclude=("^(${project_path_exclussion}|((?!\\/module\\/).)*\$|.*\\.asciidoc|.*\\.png)")
+defineFromCommit() {
+  local changeTarget=${BUILDKITE_PULL_REQUEST_BASE_BRANCH:-$BUILDKITE_BRANCH}
 
-  if [[ "$project_path" == *"x-pack/"* ]]; then
-    local pattern=("$XPACK_MODULE_PATTERN")
+  if [[ -z ${changeTarget+x} ]]; then
+    # If not a PR (no target branch) - use last commit
+    from=$(git rev-parse HEAD^)
   else
-    local pattern=("$OSS_MODULE_PATTERN")
+    # If it's a PR - add "origin/"
+    from="origin/$changeTarget"
   fi
-  local changed_modules=""
-  local module_dirs=$(find "$project_path/module" -mindepth 1 -maxdepth 1 -type d)
-  for module_dir in $module_dirs; do
-    if are_paths_changed $module_dir && ! are_changed_only_paths "${exclude[@]}"; then
-      if [[ -z "$changed_modules" ]]; then
-        changed_modules=$(basename "$module_dir")
-      else
-        changed_modules+=",$(basename "$module_dir")"
-      fi
+}
+
+getMatchingModules() {
+  local changedPaths
+  mapfile -t changedPaths < <(git diff --name-only "$from"..."$BUILDKITE_COMMIT" | grep -P "$exclude" | grep -oP "$pattern")
+  mapfile -t modulesMatched < <(printf "%s\n" "${changedPaths[@]}" | grep -o 'module/.*' | awk -F '/' '{print $2}' | sort -u)
+}
+
+addToModuleEnvVar() {
+  local module
+  for module in "${modulesMatched[@]}"; do
+    if [[ -z ${modules+x} ]]; then
+      modules="$module"
+    else
+      modules+=",$module"
     fi
   done
+}
 
-  # export MODULE="" leads to an infinite loop https://github.com/elastic/ingest-dev/issues/2993
-  if [[ ! -z $changed_modules ]]; then 
-    export MODULE="${changed_modules}"
-    echo "~~~ Set env var MODULE to [$MODULE]"
+defineModuleFromTheChangeSet() {
+  beatPath=$1
+
+  definePattern
+  defineExclusions
+  defineFromCommit
+  getMatchingModules
+
+  if [ "${#modulesMatched[@]}" -gt 0 ]; then
+    addToModuleEnvVar
+    export MODULE=$modules
+    echo "~~~ Detected file changes for some modules. Setting env var MODULE to [$MODULE]"
     echo "~~~ Resuming commands"
+  else
+    echo "~~~ No changes in modules for $beatPath"
   fi
 }