SOLR-13944: remove redundant checks in SpellCheckCollator

* After SOLR-14073, these checks become redundant and add
  additional tests for spellcheck with collapse

solr/CHANGES.txt

@@ -78,6 +78,9 @@ Other Changes
 
 * SOLR-10157: Improve error messages when unknown aggregations are specified in the request (hossman, Munendra S N)
 
+* SOLR-13944: Remove redundant checks in SpellCheckCollator and add tests for spellcheck with collapse
+  (Stefan, Munendra S N, Tomas Eduardo Fernandez Lobbe)
+
 ==================  8.5.0 ==================
 
 Consult the LUCENE_CHANGES.txt file for additional, low level, changes in this release.

solr/core/src/java/org/apache/solr/spelling/SpellCheckCollator.java

@@ -134,25 +134,15 @@ public class SpellCheckCollator {
         
         // Collate testing does not support the Collapse QParser (See SOLR-8807)
         params.remove("expand");
-        String[] filters = params.getParams(CommonParams.FQ);
-        if (filters != null) {
-          List<String> filtersToApply = new ArrayList<>(filters.length);
-          for (String fq : filters) {
-            if (!fq.startsWith("{!collapse")) {
-              filtersToApply.add(fq);
-            }
-          }
-          params.set("fq", filtersToApply.toArray(new String[filtersToApply.size()]));
-        }      
 
         // creating a request here... make sure to close it!
         ResponseBuilder checkResponse = new ResponseBuilder(
             new LocalSolrQueryRequest(ultimateResponse.req.getCore(), params),
-            new SolrQueryResponse(), Arrays.<SearchComponent> asList(queryComponent)); 
+            new SolrQueryResponse(), Arrays.asList(queryComponent));
         checkResponse.setQparser(ultimateResponse.getQparser());
         checkResponse.setFilters(ultimateResponse.getFilters());
         checkResponse.setQueryString(collationQueryStr);
-        checkResponse.components = Arrays.<SearchComponent>asList(queryComponent);
+        checkResponse.components = Arrays.asList(queryComponent);
 
         try {
           queryComponent.prepare(checkResponse);

solr/core/src/test/org/apache/solr/spelling/SpellCheckCollatorWithCollapseTest.java

@@ -18,6 +18,7 @@ package org.apache.solr.spelling;
 
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.common.params.CommonParams;
+import org.apache.solr.common.params.SolrParams;
 import org.apache.solr.common.params.SpellingParams;
 import org.apache.solr.handler.component.SpellCheckComponent;
 import org.junit.Before;
@@ -48,8 +49,15 @@ public class SpellCheckCollatorWithCollapseTest  extends SolrTestCaseJ4 {
       }
     }
     assertU(commit());
+
+    for (SolrParams params : new SolrParams[]{
+        params(CommonParams.FQ, "{!collapse field=group_i}"),
+        params(CommonParams.FQ, "${bleh}", "bleh", "{!collapse field=group_i}"), // substitution
+        params(CommonParams.FQ, "{!tag=collapser}{!collapse field=group_i}"), // with tag & collapse in localparams
+        params(CommonParams.FQ, "{!collapse tag=collapser field=group_i}")
+    }) {
       assertQ(
-        req(
+          req(params,
               SpellCheckComponent.COMPONENT_NAME, "true",
           SpellCheckComponent.SPELLCHECK_DICT, "direct",
           SpellingParams.SPELLCHECK_COUNT, "10",
@@ -59,9 +67,10 @@ public class SpellCheckCollatorWithCollapseTest  extends SolrTestCaseJ4 {
           CommonParams.Q, "a_s:lpve",
           CommonParams.QT, "/spellCheckCompRH_Direct",
           SpellingParams.SPELLCHECK_COLLATE_MAX_COLLECT_DOCS, "5",
-            CommonParams.FQ, "{!collapse field=group_i}",
           "expand", "true"),
-        "//lst[@name='spellcheck']/lst[@name='collations']/str[@name='collation']='a_s:love'");
+          "//lst[@name='spellcheck']/lst[@name='collations']/str[@name='collation']='a_s:love'"
+      );
+    }
   }
 
 }