From e61f32585955b9e9ea61397c8fbc90deff91266c Mon Sep 17 00:00:00 2001
From: Tara Drwenski <tdrwenski@ucar.edu>
Date: Thu, 27 Apr 2023 15:48:46 -0600
Subject: [PATCH] Make FilteredIterator::hasNext idempotent

---
 .../java/thredds/filesystem/s3/ControllerS3.java  |  7 +++++--
 .../thredds/filesystem/s3/TestControllerS3.java   | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/cdm/s3/src/main/java/thredds/filesystem/s3/ControllerS3.java b/cdm/s3/src/main/java/thredds/filesystem/s3/ControllerS3.java
index c15d03b144..b123a6ab34 100644
--- a/cdm/s3/src/main/java/thredds/filesystem/s3/ControllerS3.java
+++ b/cdm/s3/src/main/java/thredds/filesystem/s3/ControllerS3.java
@@ -141,6 +141,7 @@ private static class FilteredIterator implements Iterator<MFile> {
       this.mc = mc;
       this.wantDirs = wantDirs;
       this.fullInventory = false;
+      this.next = nextFilteredFile();
     }
 
     FilteredIterator(CollectionConfig mc, Iterator<MFile> iter, boolean wantDirs, boolean fullInventory) {
@@ -148,17 +149,19 @@ private static class FilteredIterator implements Iterator<MFile> {
       this.mc = mc;
       this.wantDirs = wantDirs;
       this.fullInventory = fullInventory;
+      this.next = nextFilteredFile();
     }
 
     public boolean hasNext() {
-      next = nextFilteredFile();
       return (next != null);
     }
 
     public MFile next() {
       if (next == null)
         throw new NoSuchElementException();
-      return next;
+      final MFile mFile = next;
+      next = nextFilteredFile();
+      return mFile;
     }
 
     public void remove() {
diff --git a/cdm/s3/src/test/java/thredds/filesystem/s3/TestControllerS3.java b/cdm/s3/src/test/java/thredds/filesystem/s3/TestControllerS3.java
index 86a23fa1b4..342cbec4dd 100644
--- a/cdm/s3/src/test/java/thredds/filesystem/s3/TestControllerS3.java
+++ b/cdm/s3/src/test/java/thredds/filesystem/s3/TestControllerS3.java
@@ -64,6 +64,21 @@ public static void setup() {
 
   }
 
+  @Test
+  public void shouldReturnSameValueFromHasNext() throws URISyntaxException {
+    final CdmS3Uri uri = new CdmS3Uri("cdms3:thredds-test-data");
+    final MFileFilter filter = new WildcardMatchOnName("testData.nc");
+    final CollectionConfig collectionConfig = new CollectionConfig(uri.getBucket(), uri.toString(), true, filter, null);
+    final ControllerS3 controller = new ControllerS3();
+    final Iterator<MFile> iterator = controller.getInventoryTop(collectionConfig, false);
+
+    assertThat(iterator.hasNext()).isTrue();
+    assertThat(iterator.hasNext()).isTrue();
+    iterator.next();
+    assertThat(iterator.hasNext()).isFalse();
+    assertThat(iterator.hasNext()).isFalse();
+  }
+
   //////////////////////
   // getInventoryTop() tests
   //