tdf#124881: Provide a non-empty name for pivot table's data field

Otherwise, the empty string is used by Excel, so the field arrives
unnamed, disappearing from pivot table's cells upon refresh, etc.

Change-Id: I2e0f9fad2d766829f2b06425bec24ff182e3a869
Reviewed-on: https://gerrit.libreoffice.org/71065
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

sc/inc/dputil.hxx

@@ -47,9 +47,9 @@ public:
         double fValue, const ScDPNumGroupInfo* pInfo, sal_Int32 nDatePart,
         const SvNumberFormatter* pFormatter);
 
-    static OUString getDisplayedMeasureName(const OUString& rName, ScSubTotalFunc eFunc);
+    SC_DLLPUBLIC static OUString getDisplayedMeasureName(const OUString& rName, ScSubTotalFunc eFunc);
 
-    static ScSubTotalFunc toSubTotalFunc(ScGeneralFunction eGenFunc);
+    SC_DLLPUBLIC static ScSubTotalFunc toSubTotalFunc(ScGeneralFunction eGenFunc);
 };
 
 #endif

sc/qa/unit/pivottable_filters_test.cxx

@@ -2485,7 +2485,8 @@ void ScPivotTableFiltersTest::testTdf124651()
     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", "");
+    // tdf#124881: this shouldn't be an empty string
+    assertXPath(pDoc, "/x:pivotTableDefinition/x:dataFields/x:dataField", "name", "Sum - num");
 }
 
 void ScPivotTableFiltersTest::testTdf124736()

sc/source/filter/excel/xepivotxml.cxx

@@ -1078,13 +1078,16 @@ void XclExpXmlPivotTables::SavePivotTableXml( XclExpXmlStream& rStrm, const ScDP
             long nDimIdx = rDataField.mnPos;
             assert(aCachedDims[nDimIdx]); // the loop above should have screened for NULL's.
             const ScDPSaveDimension& rDim = *rDataField.mpDim;
-            const boost::optional<OUString> & pName = rDim.GetLayoutName();
+            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() : "";
+            // dataField element.
+            // tdf#124881: try to create a meaningful name; don't use empty string.
+            if (!pName)
+                pName = ScDPUtil::getDisplayedMeasureName(
+                    rDim.GetName(), ScDPUtil::toSubTotalFunc(rDim.GetFunction()));
             auto pItemAttList = sax_fastparser::FastSerializerHelper::createAttrList();
-            pItemAttList->add(XML_name, sName);
+            pItemAttList->add(XML_name, pName->toUtf8());
             pItemAttList->add(XML_fld, OString::number(nDimIdx));
             const char* pSubtotal = toOOXMLSubtotalType(rDim.GetFunction());
             if (pSubtotal)