From d3a47eeb70166d1ffe66ffd1cf7f3926dbc89c4d Mon Sep 17 00:00:00 2001
From: Pascal Christoph <christoph@hbz-nrw.de>
Date: Fri, 27 Sep 2024 15:56:40 +0200
Subject: [PATCH] Don't insert a line break when nothing is processed (#543)

---
 .../org/metafacture/io/ObjectFileWriter.java  | 23 +++++++++++--------
 .../metafacture/io/ObjectFileWriterTest.java  | 20 +++++++++++-----
 2 files changed, 27 insertions(+), 16 deletions(-)

diff --git a/metafacture-io/src/main/java/org/metafacture/io/ObjectFileWriter.java b/metafacture-io/src/main/java/org/metafacture/io/ObjectFileWriter.java
index f7462982..36d45426 100644
--- a/metafacture-io/src/main/java/org/metafacture/io/ObjectFileWriter.java
+++ b/metafacture-io/src/main/java/org/metafacture/io/ObjectFileWriter.java
@@ -90,18 +90,21 @@ public void setCompression(final String compression) {
     @Override
     public void process(final T obj) {
         assert !closed;
-        try {
-            if (firstObject) {
-                getWriter().write(getHeader());
-                firstObject = false;
+        final String objStr = obj.toString();
+        if (!objStr.isEmpty()) {
+            try {
+                if (firstObject) {
+                    getWriter().write(getHeader());
+                    firstObject = false;
+                }
+                else {
+                    getWriter().write(getSeparator());
+                }
+                getWriter().write(objStr);
             }
-            else {
-                getWriter().write(getSeparator());
+            catch (final IOException e) {
+                throw new MetafactureException(e);
             }
-            getWriter().write(obj.toString());
-        }
-        catch (final IOException e) {
-            throw new MetafactureException(e);
         }
     }
 
diff --git a/metafacture-io/src/test/java/org/metafacture/io/ObjectFileWriterTest.java b/metafacture-io/src/test/java/org/metafacture/io/ObjectFileWriterTest.java
index 64d877fb..77d9ad61 100644
--- a/metafacture-io/src/test/java/org/metafacture/io/ObjectFileWriterTest.java
+++ b/metafacture-io/src/test/java/org/metafacture/io/ObjectFileWriterTest.java
@@ -20,6 +20,12 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assume.assumeFalse;
 
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import org.metafacture.commons.ResourceUtil;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
@@ -28,12 +34,6 @@
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 
-import org.junit.Before;
-import org.junit.Rule;
-import org.junit.Test;
-import org.junit.rules.TemporaryFolder;
-import org.metafacture.commons.ResourceUtil;
-
 /**
  * Tests for class {@link ObjectFileWriter}.
  *
@@ -105,6 +105,14 @@ public void shouldIncrementCountOnResetBeforeStartingNewFile() throws IOExceptio
         assertTrue(new File(tempFolder.getRoot(), "test-1").exists());
     }
 
+    @Test
+    public void issue543_shouldResultEmptyWhenNothingIsProcessed() throws IOException {
+        writer.process("");
+        writer.closeStream();
+
+        assertOutput("");
+    }
+
     @Override
     protected ConfigurableObjectWriter<String> getWriter() {
         return writer;