tdf#124651: always write "name" attribute to dataField element

Despite being optional as per ECMA-376-1:2016, Excel 2016 seems to
require the presence of "name" attribute in dataField element of
pivot table definition, so make sure to write at least empty string
there.

Change-Id: Iaab5674f86b7dd0b267776678e11af47086635d7
Reviewed-on: https://gerrit.libreoffice.org/70522Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>
Tested-by: Mike Kaganski <mike.kaganski@collabora.com>

sc/qa/unit/pivottable_filters_test.cxx

@@ -85,6 +85,7 @@ public:
     void testTdf112106();
     void testTdf123923();
     void testTdf123939();
+    void testTdf124651();
 
     CPPUNIT_TEST_SUITE(ScPivotTableFiltersTest);
 
@@ -127,6 +128,7 @@ public:
     CPPUNIT_TEST(testTdf112106);
     CPPUNIT_TEST(testTdf123923);
     CPPUNIT_TEST(testTdf123939);
+    CPPUNIT_TEST(testTdf124651);
 
     CPPUNIT_TEST_SUITE_END();
 
@@ -2430,6 +2432,19 @@ void ScPivotTableFiltersTest::testTdf123939()
                 "containsMixedTypes", "1");
 }
 
+void ScPivotTableFiltersTest::testTdf124651()
+{
+    ScDocShellRef xDocSh = loadDoc("tdf124651_simplePivotTable.", FORMAT_ODS);
+    CPPUNIT_ASSERT(xDocSh.is());
+
+    xmlDocPtr pDoc = XPathHelper::parseExport2(*this, *xDocSh, m_xSFactory,
+        "xl/pivotTables/pivotTable1.xml", FORMAT_XLSX);
+    CPPUNIT_ASSERT(pDoc);
+    // We have to export name attribute, even though it's optional according to ECMA-376 standard,
+    // because Excel (at least 2016) seems to require it.
+    assertXPath(pDoc, "/x:pivotTableDefinition/x:dataFields/x:dataField", "name", "");
+}
+
 CPPUNIT_TEST_SUITE_REGISTRATION(ScPivotTableFiltersTest);
 
 CPPUNIT_PLUGIN_IMPLEMENT();

sc/source/filter/excel/xepivotxml.cxx

@@ -947,9 +947,12 @@ void XclExpXmlPivotTables::SavePivotTableXml( XclExpXmlStream& rStrm, const ScDP
             assert(aCachedDims[nDimIdx]); // the loop above should have screened for NULL's.
             const ScDPSaveDimension& rDim = *rDataField.mpDim;
             const boost::optional<OUString> & pName = rDim.GetLayoutName();
+            // tdf#124651: despite being optional in CT_DataField according to ECMA-376 Part 1,
+            // Excel (at least 2016) seems to insist on the presence of "name" attribute in
+            // dataField element, even if empty
+            const OString sName = pName ? pName->toUtf8() : "";
             pPivotStrm->write("<")->writeId(XML_dataField);
-            if (pName)
-                rStrm.WriteAttributes(XML_name, pName->toUtf8(), FSEND);
+            rStrm.WriteAttributes(XML_name, sName, FSEND);
 
             rStrm.WriteAttributes(XML_fld, OString::number(nDimIdx).getStr(), FSEND);