GET SM policies return empty list when ism config index does not exist (#1072)

(cherry picked from commit 67292ca)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]

src/main/kotlin/org/opensearch/indexmanagement/snapshotmanagement/api/transport/get/TransportGetSMPoliciesAction.kt

@@ -17,6 +17,7 @@ import org.opensearch.common.settings.Settings
 import org.opensearch.common.util.concurrent.ThreadContext
 import org.opensearch.commons.authuser.User
 import org.opensearch.index.IndexNotFoundException
+import org.opensearch.ExceptionsHelper
 import org.opensearch.index.query.BoolQueryBuilder
 import org.opensearch.index.query.ExistsQueryBuilder
 import org.opensearch.index.query.Operator
@@ -69,12 +70,18 @@ class TransportGetSMPoliciesAction @Inject constructor(
 
     private suspend fun getAllPolicies(searchParams: SearchParams, user: User?): Pair<List<SMPolicy>, Long> {
         val searchRequest = getAllPoliciesRequest(searchParams, user)
-        val searchResponse: SearchResponse = try {
-            client.suspendUntil { search(searchRequest, it) }
-        } catch (e: IndexNotFoundException) {
-            throw OpenSearchStatusException("Snapshot management config index not found", RestStatus.NOT_FOUND)
+        return try {
+            val searchResponse = client.suspendUntil { search(searchRequest, it) }
+            parseGetAllPoliciesResponse(searchResponse)
+        } catch (e: Exception) {
+            val unwrappedException = ExceptionsHelper.unwrapCause(e) as Exception
+            if (unwrappedException is IndexNotFoundException) {
+                // config index hasn't been initialized, catch this here and show empty result for policies
+                Pair(emptyList(), 0L)
+            } else {
+                throw unwrappedException
+            }
         }
-        return parseGetAllPoliciesResponse(searchResponse)
     }
 
     private fun getAllPoliciesRequest(searchParams: SearchParams, user: User?): SearchRequest {

src/test/kotlin/org/opensearch/indexmanagement/snapshotmanagement/resthandler/RestGetSnapshotManagementIT.kt

@@ -80,6 +80,20 @@ class RestGetSnapshotManagementIT : SnapshotManagementRestTestCase() {
         }
     }
 
+    @Throws(Exception::class)
+    @Suppress("UNCHECKED_CAST")
+    fun `test getting all snapshot management policies when config index doesn't exist`() {
+        val response = client().makeRequest(
+            "GET", IndexManagementPlugin.SM_POLICIES_URI, null,
+            BasicHeader(HttpHeaders.CONTENT_TYPE, "application/json")
+        )
+        val map = response.asMap()
+        val totalPolicies = map["total_policies"] as Int
+        val responsePolicies = map["policies"] as List<Map<String, Any?>>
+        assertTrue("Total policies is 0", totalPolicies == 0)
+        assertTrue("Response list of policies is empty", responsePolicies.isEmpty())
+    }
+
     @Throws(Exception::class)
     @Suppress("UNCHECKED_CAST")
     fun `test getting all snapshot management policies with search params`() {