GH-2949: Fix retryCount handling in the DefaultMessagePropertiesConverter

Fixes: #2949
Issue link: #2949

* The handling of `retryCount` is moved into `convertHeadersIfNecessary()`,
so that we can still return a `Collections.emptyMap()` if there are no headers
in the source `MessageProperties` and no `retryCount` to add.

Signed-off-by: Johan Kaving <[email protected]>

[[email protected] improve commit message]

**Auto-cherry-pick to `3.2.x`**

Signed-off-by: Artem Bilan <[email protected]>

Author: jkaving

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/support/DefaultMessagePropertiesConverter.java

@@ -43,6 +43,7 @@
  * @author Raylax Grey
  * @author Artem Bilan
  * @author Ngoc Nhan
+ * @author Johan Kaving
  *
  * @since 1.0
  */
@@ -155,11 +156,7 @@ else if (MessageProperties.RETRY_COUNT.equals(key)) {
 	@Override
 	public BasicProperties fromMessageProperties(final MessageProperties source, final String charset) {
 		BasicProperties.Builder target = new BasicProperties.Builder();
-		Map<String, Object> headers = convertHeadersIfNecessary(source.getHeaders());
-		long retryCount = source.getRetryCount();
-		if (retryCount > 0) {
-			headers.put(MessageProperties.RETRY_COUNT, retryCount);
-		}
+		Map<String, Object> headers = convertHeadersIfNecessary(source);
 		target.headers(headers)
 			.timestamp(source.getTimestamp())
 			.messageId(source.getMessageId())
@@ -186,14 +183,20 @@ public BasicProperties fromMessageProperties(final MessageProperties source, fin
 		return target.build();
 	}
 
-	private Map<String, Object> convertHeadersIfNecessary(Map<String, Object> headers) {
-		if (CollectionUtils.isEmpty(headers)) {
+	private Map<String, Object> convertHeadersIfNecessary(MessageProperties source) {
+		Map<String, Object> headers = source.getHeaders();
+		long retryCount = source.getRetryCount();
+
+		if (CollectionUtils.isEmpty(headers) && retryCount == 0) {
 			return Collections.emptyMap();
 		}
 		Map<String, Object> writableHeaders = new HashMap<>();
 		for (Map.Entry<String, Object> entry : headers.entrySet()) {
 			writableHeaders.put(entry.getKey(), this.convertHeaderValueIfNecessary(entry.getValue()));
 		}
+		if (retryCount > 0) {
+			writableHeaders.put(MessageProperties.RETRY_COUNT, retryCount);
+		}
 		return writableHeaders;
 	}
 

spring-rabbit/src/test/java/org/springframework/amqp/rabbit/support/DefaultMessagePropertiesConverterTests.java

@@ -38,6 +38,7 @@
 /**
  * @author Soeren Unruh
  * @author Gary Russell
+ * @author Johan Kaving
  * @since 1.3
  */
 public class DefaultMessagePropertiesConverterTests {
@@ -200,6 +201,17 @@ public void testClassHeader() {
 		assertThat(basic.getHeaders().get("aClass")).isEqualTo(getClass().getName());
 	}
 
+	@Test
+	public void testRetryCount() {
+		MessageProperties props = new MessageProperties();
+		props.incrementRetryCount();
+		BasicProperties basic = new DefaultMessagePropertiesConverter().fromMessageProperties(props, "UTF8");
+		assertThat(basic.getHeaders().get(MessageProperties.RETRY_COUNT)).isEqualTo(1L);
+		props.incrementRetryCount();
+		basic = new DefaultMessagePropertiesConverter().fromMessageProperties(props, "UTF8");
+		assertThat(basic.getHeaders().get(MessageProperties.RETRY_COUNT)).isEqualTo(2L);
+	}
+
 	private static class Foo {
 
 		Foo() {