don't show nulled out fields with show=schema

Author: kotman12

solr/core/src/java/org/apache/solr/handler/admin/LukeRequestHandler.java

@@ -384,7 +384,11 @@ private void mergeDistributedResponses(SolrQueryResponse rsp, List<ShardResponse
       NamedList<Object> shardRsp = srsp.getSolrResponse().getResponse();
       LukeResponse lukeRsp = new LukeResponse();
       lukeRsp.setResponse(shardRsp);
-      ShardData shardData = new ShardData(shardAddress(srsp), lukeRsp.getFieldInfo());
+      // Only process field info if the shard explicitly included it in its response.
+      // LukeResponse.getFieldInfo() falls back to schema.fields which has incomplete data.
+      Map<String, LukeResponse.FieldInfo> fieldInfo =
+          shardRsp.get(RSP_FIELDS) != null ? lukeRsp.getFieldInfo() : null;
+      ShardData shardData = new ShardData(shardAddress(srsp), fieldInfo);
 
       NamedList<Object> shardIndex = lukeRsp.getIndexInfo();
       if (shardIndex != null) {

solr/core/src/test/org/apache/solr/handler/admin/LukeRequestHandlerDistribTest.java

@@ -289,6 +289,38 @@ public void testSparseShards() throws Exception {
     }
   }
 
+  @Test
+  @SuppressWarnings("unchecked")
+  public void testDistribShowSchema() throws Exception {
+    ModifiableSolrParams params = new ModifiableSolrParams();
+    params.set("distrib", "true");
+    params.set("show", "schema");
+
+    LukeResponse rsp = requestLuke(COLLECTION, params);
+
+    NamedList<Object> raw = rsp.getResponse();
+    NamedList<Object> schema = (NamedList<Object>) raw.get("schema");
+    assertNotNull("schema section should be present", schema);
+
+    NamedList<Object> fields = (NamedList<Object>) schema.get("fields");
+    assertNotNull("schema fields should be present", fields);
+    assertNotNull("'id' should be in schema fields", fields.get("id"));
+    assertNotNull("'name' should be in schema fields", fields.get("name"));
+
+    assertNotNull("dynamicFields should be present", schema.get("dynamicFields"));
+    assertNotNull("uniqueKeyField should be present", schema.get("uniqueKeyField"));
+    assertEquals("uniqueKeyField should be 'id'", "id", schema.get("uniqueKeyField"));
+    assertNotNull("types should be present", schema.get("types"));
+    assertNotNull("similarity should be present", schema.get("similarity"));
+
+    // show=schema should not produce merged top-level fields (matches local mode behavior)
+    assertNull("top-level fields should not be present with show=schema", raw.get("fields"));
+
+    // Shards are present for consistency: each shard entry mirrors the per-shard index info,
+    // just as the top-level index section is present in local mode with show=schema
+    assertNotNull("shards should still be present with show=schema", raw.get("shards"));
+  }
+
   @Test
   public void testDistribTrueOnSingleShardFallsBackToLocal() throws Exception {
     String singleShardCollection = "lukeSingleShard";