Add a whitespace trimming mode to ManifestAppenderTransformer

src/main/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformer.groovy

@@ -41,6 +41,9 @@ class ManifestAppenderTransformer implements Transformer {
 
     private byte[] manifestContents = []
     private final List<Tuple2<String, ? extends Comparable<?>>> attributes = []
+    private boolean trimTrailingWhitespace = false
+
+    ManifestAppenderTransformer() {}
 
     List<Tuple2<String, ? extends Comparable<?>>> getAttributes() { attributes }
 
@@ -49,6 +52,11 @@ class ManifestAppenderTransformer implements Transformer {
         this
     }
 
+    ManifestAppenderTransformer trimTrailingWhitespace() {
+        trimTrailingWhitespace = true
+        this
+    }
+
     @Override
     boolean canTransformResource(FileTreeElement element) {
         MANIFEST_NAME.equalsIgnoreCase(element.relativePath.pathString)
@@ -72,7 +80,13 @@ class ManifestAppenderTransformer implements Transformer {
         ZipEntry entry = new ZipEntry(MANIFEST_NAME)
         entry.time = TransformerContext.getEntryTimestamp(preserveFileTimestamps, entry.time)
         os.putNextEntry(entry)
-        os.write(manifestContents)
+
+        if (trimTrailingWhitespace) {
+            os.write(trimTrailingWhitespace(manifestContents))
+            os.write(EOL)
+        } else {
+            os.write(manifestContents)
+        }
 
         if (!attributes.isEmpty()) {
             for (attribute in attributes) {
@@ -85,4 +99,8 @@ class ManifestAppenderTransformer implements Transformer {
             attributes.clear()
         }
     }
+
+    static byte[] trimTrailingWhitespace(byte[] contents) {
+        new String(contents, UTF_8).replaceFirst("\\s++\$", "").getBytes(UTF_8)
+    }
 }

src/test/groovy/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformerTest.groovy

@@ -123,6 +123,35 @@ class ManifestAppenderTransformerTest extends TransformerTestSupport {
         assertEquals(sourceLines, targetLines)
     }
 
+    @Test
+    void testTransformationTrimmingTrailingWhitespace() {
+        def sourceLines = getResourceStream(MANIFEST_NAME).readLines()
+        def trimmedContent = sourceLines
+        while (trimmedContent.last().trim().isEmpty()) {
+            trimmedContent.removeLast()
+        }
+
+        transformer.with {
+            trimTrailingWhitespace()
+            append('Name', 'org/foo/bar/')
+            transform(new TransformerContext(MANIFEST_NAME, getResourceStream(MANIFEST_NAME), Collections.<Relocator>emptyList(), new ShadowStats()))
+        }
+
+        def testableZipFile = File.createTempFile("testable-zip-file-", ".jar")
+        def fileOutputStream = new FileOutputStream(testableZipFile)
+        def bufferedOutputStream = new BufferedOutputStream(fileOutputStream)
+        def zipOutputStream = new ZipOutputStream(bufferedOutputStream)
+
+        try {
+            transformer.modifyOutputStream(zipOutputStream, true)
+        } finally {
+            zipOutputStream.close()
+        }
+
+        def targetLines = readFrom(testableZipFile, MANIFEST_NAME)
+        assertEquals(trimmedContent + "Name: org/foo/bar/" + "", targetLines)
+    }
+
     static List<String> readFrom(File jarFile, String resourceName) {
         def zip = new ZipFile(jarFile)
         try {