Update the "write skip count" when items are removed from chunks during write

Resolves #4514

Signed-off-by: Florian Hof <florian.hof@sbb.ch>

Author: florianhof

spring-batch-core/src/main/java/org/springframework/batch/core/step/StepContribution.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2023 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -157,6 +157,15 @@ public void incrementWriteSkipCount() {
 		writeSkipCount++;
 	}
 
+	/**
+	 * Increment the write skip count for this contribution.
+	 * @param count The {@code long} amount to increment by.
+	 * @since 6.0.0
+	 */
+	public void incrementWriteSkipCount(long count) {
+		writeSkipCount += count;
+	}
+
 	/**
 	 *
 	 */

spring-batch-core/src/main/java/org/springframework/batch/core/step/item/FaultTolerantChunkProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2024 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -347,6 +347,7 @@ protected void write(final StepContribution contribution, final Chunk<I> inputs,
 					stopTimer(sample, contribution.getStepExecution(), "chunk.write", status, "Chunk writing");
 				}
 				contribution.incrementWriteCount(outputs.size());
+				contribution.incrementWriteSkipCount(outputs.getSkipsSize());
 			}
 			else {
 				scan(contribution, inputs, outputs, chunkMonitor, false);

spring-batch-core/src/main/java/org/springframework/batch/core/step/item/SimpleChunkProcessor.java

@@ -309,6 +309,7 @@ protected void write(StepContribution contribution, Chunk<I> inputs, Chunk<O> ou
 			stopTimer(sample, contribution.getStepExecution(), "chunk.write", status, "Chunk writing");
 		}
 		contribution.incrementWriteCount(outputs.size());
+		contribution.incrementWriteSkipCount(outputs.getSkipsSize());
 	}
 
 	protected Chunk<O> transform(StepContribution contribution, Chunk<I> inputs) throws Exception {

spring-batch-core/src/test/java/org/springframework/batch/core/step/item/FaultTolerantChunkProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2024 the original author or authors.
+ * Copyright 2008-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -230,6 +230,25 @@ void testWriteSkipOnException() throws Exception {
 		assertEquals(0, contribution.getFilterCount());
 	}
 
+	@Test
+	void testWriteSkipOnIteratorRemove() throws Exception {
+		processor.setItemWriter(chunk -> {
+			Chunk<? extends String>.ChunkIterator iterator = chunk.iterator();
+			while (iterator.hasNext()) {
+				String item = iterator.next();
+				if (item.equals("skip")) {
+					iterator.remove((Exception) null);
+				}
+			}
+		});
+		Chunk<String> inputs = new Chunk<>(Arrays.asList("3", "skip", "2"));
+		processor.process(contribution, inputs);
+		assertEquals(1, contribution.getSkipCount());
+		assertEquals(2, contribution.getWriteCount());
+		assertEquals(1, contribution.getWriteSkipCount());
+		assertEquals(0, contribution.getFilterCount());
+	}
+
 	@Test
 	void testWriteSkipOnExceptionWithTrivialChunk() throws Exception {
 		processor.setWriteSkipPolicy(new AlwaysSkipItemSkipPolicy());

spring-batch-core/src/test/java/org/springframework/batch/core/step/item/SimpleChunkProcessorTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2024 the original author or authors.
+ * Copyright 2008-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -51,7 +51,16 @@ public void write(Chunk<? extends String> chunk) throws Exception {
 			if (chunk.getItems().contains("fail")) {
 				throw new RuntimeException("Planned failure!");
 			}
-			list.addAll(chunk.getItems());
+			Chunk<? extends String>.ChunkIterator iterator = chunk.iterator();
+			while (iterator.hasNext()) {
+				String item = iterator.next();
+				if (item.equals("skip")) {
+					iterator.remove((Exception) null);
+				}
+				else {
+					list.add(item);
+				}
+			}
 		}
 	});
 
@@ -88,4 +97,15 @@ void testTransform() throws Exception {
 		assertTrue(outputs.isEnd());
 	}
 
+	@Test
+	void testWriteWithSkip() throws Exception {
+		Chunk<String> inputs = new Chunk<>();
+		inputs.add("foo");
+		inputs.add("skip");
+		inputs.add("bar");
+		processor.process(contribution, inputs);
+		assertEquals(2, contribution.getWriteCount());
+		assertEquals(1, contribution.getWriteSkipCount());
+	}
+
 }

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/Chunk.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2024 the original author or authors.
+ * Copyright 2006-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -152,6 +152,14 @@ public int size() {
 		return items.size();
 	}
 
+	/**
+	 * @return the number of skipped items
+	 * @since 6.0.0
+	 */
+	public int getSkipsSize() {
+		return skips.size();
+	}
+
 	/**
 	 * Flag to indicate if the source data is exhausted.
 	 *