Add new filter to merge suggestions before CleanOverlappingFilter rem…

languagetool-core/src/main/java/org/languagetool/JLanguageTool.java

@@ -1067,6 +1067,7 @@ private List<RuleMatch> filterMatches(AnnotatedText annotatedText, RuleSet rules
 
     ruleMatches = new SameRuleGroupFilter().filter(ruleMatches);
     // no sorting: SameRuleGroupFilter sorts rule matches already
+    ruleMatches = new LanguageDependentMergeSuggestionFilter(language, rules).filter(ruleMatches, annotatedText);
     if (cleanOverlappingMatches) {
       ruleMatches = new CleanOverlappingFilter(language, userConfig.getHidePremiumMatches()).filter(ruleMatches);
     }

languagetool-core/src/main/java/org/languagetool/Language.java

@@ -25,6 +25,7 @@
 import org.languagetool.language.Contributor;
 import org.languagetool.languagemodel.LanguageModel;
 import org.languagetool.languagemodel.LuceneLanguageModel;
+import org.languagetool.markup.AnnotatedText;
 import org.languagetool.rules.*;
 import org.languagetool.rules.patterns.AbstractPatternRule;
 import org.languagetool.rules.patterns.PatternRuleLoader;
@@ -941,4 +942,16 @@ public String getConsistencyRulePrefix() {
   public RuleMatch adjustMatch(RuleMatch rm, List<String> features) {
     return rm;
   }
+
+  /**
+   * This function is called by JLanguageTool before CleanOverlappingFilter removes overlapping ruleMatches
+   *
+   * @param ruleMatches
+   * @param text
+   * @param enabledRules
+   * @return filtered ruleMatches
+   */
+  public List<RuleMatch> mergeSuggestions(List<RuleMatch> ruleMatches, AnnotatedText text, Set<String> enabledRules) {
+    return ruleMatches;
+  }
 }

languagetool-core/src/main/java/org/languagetool/rules/LanguageDependentMergeSuggestionFilter.java

@@ -0,0 +1,43 @@
+/*
+ * LanguageTool, a natural language style checker
+ * Copyright (c) 2023.  Stefan Viol (https://stevio.de)
+ *
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2.1 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
+ *  USA
+ */
+
+package org.languagetool.rules;
+
+import org.languagetool.Language;
+import org.languagetool.markup.AnnotatedText;
+import org.languagetool.rules.patterns.RuleSet;
+
+import java.util.List;
+import java.util.Set;
+
+public class LanguageDependentMergeSuggestionFilter implements RuleMatchFilter {
+
+  private final Language language;
+  private final Set<String> enabledRules;
+  public LanguageDependentMergeSuggestionFilter(Language language, RuleSet rules) {
+    this.language = language;
+    this.enabledRules = rules.allRuleIds();
+  }
+
+  @Override
+  public List<RuleMatch> filter(List<RuleMatch> ruleMatches, AnnotatedText text) {
+    return language.mergeSuggestions(ruleMatches, text, enabledRules);
+  }
+}