[SYSTEMDS-3813] Fix incorrect file format on list write

The writing of lists always produced individual matrix/frame files in
text format (even though the metadata of the list indicated otherwise).
This patch now properly writes the individual files in the correct
format.

Author: mboehm7

src/main/java/org/apache/sysds/lops/Data.java

@@ -276,12 +276,10 @@ else if (_op.isWrite()) {
 		OutputParameters oparams = getOutputParameters();
 		if ( _op.isWrite() ) {
 			sb.append( OPERAND_DELIMITOR );
-			FileFormat fmt = null;
-			if ( getDataType() == DataType.MATRIX || getDataType() == DataType.FRAME )
-				fmt = oparams.getFormat();
-			else // scalars will always be written in text format
-				fmt = FileFormat.TEXT;
-
+			// scalars will always be written in text format
+			FileFormat fmt = getDataType().isScalar() ?
+				FileFormat.TEXT : oparams.getFormat();
+			
 			//format literal or variable
 			Lop fmtLop = _inputParams.get(DataExpression.FORMAT_TYPE);
 			String fmtLabel = (fmt!=FileFormat.UNKNOWN) ? fmt.toString() : fmtLop.getOutputParameters().getLabel();

src/main/java/org/apache/sysds/runtime/instructions/cp/VariableCPInstruction.java

@@ -1084,7 +1084,8 @@ else if( getInput1().getDataType() == DataType.TENSOR ) {
 		}
 		else if( getInput1().getDataType() == DataType.LIST ) {
 			ListObject lo = ec.getListObject(getInput1().getName());
-			ListWriter.writeListToHDFS(lo, fname, fmtStr, _formatProperties);
+			int blen = Integer.parseInt(getInput4().getName());
+			ListWriter.writeListToHDFS(lo, fname, fmtStr, new FileFormatProperties(blen));
 		}
 	}
 

src/test/java/org/apache/sysds/test/functions/io/ReadWriteListTest.java

@@ -25,6 +25,7 @@
 import org.apache.commons.logging.LogFactory;
 import org.apache.sysds.common.Types.ExecMode;
 import org.apache.sysds.common.Types.FileFormat;
+import org.apache.sysds.runtime.meta.MetaDataAll;
 import org.apache.sysds.runtime.util.HDFSTool;
 import org.apache.sysds.test.AutomatedTestBase;
 import org.apache.sysds.test.TestConfiguration;
@@ -120,8 +121,14 @@ private void runListReadWriteTest(boolean named, FileFormat format, ExecMode mod
 			fullDMLScriptName = HOME + TEST_NAME2 + ".dml";
 			programArgs = new String[]{"-args", output("L"), output("R2")};
 			runTest(true, false, null, -1);
-			double val2 = HDFSTool.readDoubleFromHDFSFile(output("R2"));
 
+			//check meta data, incl implicitly format 
+			MetaDataAll meta = getMetaData("L", OUTPUT_DIR);
+			Assert.assertEquals(format.toString(), meta.getFormatTypeString());
+			Assert.assertEquals(4, meta.getDim1());
+			Assert.assertEquals(1, meta.getDim2());
+			
+			double val2 = HDFSTool.readDoubleFromHDFSFile(output("R2"));
 			Assert.assertEquals(Double.valueOf(val1), Double.valueOf(val2), eps);
 		}
 		catch(IOException e) {