make all Directory.listAll's sort, and add BaseDirectoryTestCase; add TODO; suppress VirusCheckingFS for another test

lucene/core/src/java/org/apache/lucene/index/IndexFileDeleter.java

@@ -699,14 +699,15 @@ final class IndexFileDeleter implements Closeable {
       infoStream.message("IFD", "delete \"" + names + "\"");
     }
 
-    // nocommit put annoying windows-specific segments_N heroics back?
-
     for(String name : names) {
       try {
         directory.deleteFile(name);
       } catch (NoSuchFileException | FileNotFoundException e) {
         // IndexWriter should only ask us to delete files it knows it wrote, so if we hit this, something is wrong!
+
         if (Constants.WINDOWS) {
+          // TODO: can we remove this OS-specific hacky logic?  If windows deleteFile is buggy, we should instead contain this workaround in
+          // a WindowsFSDirectory ...
           // LUCENE-6684: we suppress this assert for Windows, since a file could be in a confusing "pending delete" state, and falsely
           // return NSFE/FNFE
         } else {

lucene/core/src/java/org/apache/lucene/index/IndexWriter.java

@@ -754,8 +754,9 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
    *           IO error
    */
   public IndexWriter(Directory d, IndexWriterConfig conf) throws IOException {
-    if (d instanceof FSDirectory && ((FSDirectory) d).checkPendingDeletions()) {
-      throw new IllegalArgumentException("Directory still has pending deleted files");
+    Directory unwrapped = FilterDirectory.unwrap(d);
+    if (unwrapped instanceof FSDirectory && ((FSDirectory) unwrapped).checkPendingDeletions()) {
+      throw new IllegalArgumentException("Directory still has pending deleted files; cannot initialize IndexWriter");
     }
 
     conf.setIndexWriter(this); // prevent reuse by other instances

lucene/core/src/java/org/apache/lucene/store/Directory.java

@@ -43,7 +43,7 @@ import org.apache.lucene.util.IOUtils;
 public abstract class Directory implements Closeable {
 
   /**
-   * Returns an array of strings, one for each entry in the directory.
+   * Returns an array of strings, one for each entry in the directory, in sorted (UTF16, java's String.compare) order.
    * 
    * @throws IOException in case of IO error
    */

lucene/core/src/java/org/apache/lucene/store/RAMDirectory.java

@@ -21,6 +21,7 @@ import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.nio.file.Files;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
@@ -119,8 +120,12 @@ public class RAMDirectory extends BaseDirectory implements Accountable {
     // concurrently
     Set<String> fileNames = fileMap.keySet();
     List<String> names = new ArrayList<>(fileNames.size());
-    for (String name : fileNames) names.add(name);
-    return names.toArray(new String[names.size()]);
+    for (String name : fileNames) {
+      names.add(name);
+    }
+    String[] namesArray = names.toArray(new String[names.size()]);
+    Arrays.sort(namesArray);
+    return namesArray;
   }
 
   public final boolean fileNameExists(String name) {

lucene/core/src/test/org/apache/lucene/index/TestIndexWriter.java

@@ -2738,7 +2738,7 @@ public class TestIndexWriter extends LuceneTestCase {
       try {
         w = new IndexWriter(dir, iwc);
       } catch (IllegalArgumentException iae) {
-        assertEquals("Directory still has pending deleted files", iae.getMessage());
+        assertEquals("Directory still has pending deleted files; cannot initialize IndexWriter", iae.getMessage());
       }
       in.close();
     }

lucene/suggest/src/java/org/apache/lucene/search/suggest/analyzing/AnalyzingInfixSuggester.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.io.StringReader;
 import java.nio.file.Path;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
@@ -58,8 +59,8 @@ import org.apache.lucene.index.SegmentReader;
 import org.apache.lucene.index.SortedSetDocValues;
 import org.apache.lucene.index.SortingMergePolicy;
 import org.apache.lucene.index.Term;
-import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanClause.Occur;
+import org.apache.lucene.search.BooleanClause;
 import org.apache.lucene.search.BooleanQuery;
 import org.apache.lucene.search.Collector;
 import org.apache.lucene.search.EarlyTerminatingSortingCollector;

lucene/suggest/src/test/org/apache/lucene/search/suggest/analyzing/AnalyzingInfixSuggesterTest.java

@@ -45,10 +45,12 @@ import org.apache.lucene.search.suggest.Lookup.LookupResult;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.IOUtils;
+import org.apache.lucene.util.LuceneTestCase.SuppressFileSystems;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.TestUtil;
 import org.junit.Test;
 
+@SuppressFileSystems("VirusCheckingFS")
 public class AnalyzingInfixSuggesterTest extends LuceneTestCase {
 
   public void testBasic() throws Exception {

lucene/suggest/src/test/org/apache/lucene/search/suggest/analyzing/BlendedInfixSuggesterTest.java

@@ -33,9 +33,11 @@ import org.apache.lucene.search.suggest.Input;
 import org.apache.lucene.search.suggest.InputArrayIterator;
 import org.apache.lucene.search.suggest.Lookup;
 import org.apache.lucene.util.BytesRef;
+import org.apache.lucene.util.LuceneTestCase.SuppressFileSystems;
 import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.TestUtil;
 
+@SuppressFileSystems("VirusCheckingFS")
 public class BlendedInfixSuggesterTest extends LuceneTestCase {