exceljs · Siemienik · Oct 5, 2020 · Jul 7, 2020 · Jul 7, 2020 · Jul 26, 2020
diff --git a/lib/doc/worksheet.js b/lib/doc/worksheet.js
@@ -411,7 +411,8 @@ class Worksheet {
   spliceRows(start, count, ...inserts) {
     // same problem as row.splice, except worse.
     const nKeep = start + count;
-    const nExpand = inserts.length - count;
+    const nInserts = inserts.length;
+    const nExpand = nInserts - count;
     const nEnd = this._rows.length;
     let i;
     let rSrc;
@@ -445,6 +446,16 @@ class Worksheet {
           // eslint-disable-next-line no-loop-func
           rSrc.eachCell({includeEmpty: true}, (cell, colNumber) => {
             rDst.getCell(colNumber).style = cell.style;
+
+            // remerge cells accounting for insert offset
+            if (cell._value.constructor.name === 'MergeValue') {
+              const cellToBeMerged = this.getRow(cell._row._number + nInserts).getCell(colNumber);
+              const prevMaster = cell._value._master;
+              const newMaster = this
+                .getRow(prevMaster._row._number + nInserts)
+                .getCell(prevMaster._column._number)
+              cellToBeMerged.merge(newMaster);
+            }
           });
         } else {
           this._rows[i + nExpand - 1] = undefined;
@@ -453,14 +464,14 @@ class Worksheet {
     }
 
     // now copy over the new values
-    for (i = 0; i < inserts.length; i++) {
+    for (i = 0; i < nInserts; i++) {
       const rDst = this.getRow(start + i);
       rDst.style = {};
       rDst.values = inserts[i];
     }
 
     // account for defined names
-    this.workbook.definedNames.spliceRows(this.name, start, count, inserts.length);
+    this.workbook.definedNames.spliceRows(this.name, start, count, nInserts);
   }
 
   // iterate over every row in the worksheet, including maybe empty rows

diff --git a/spec/unit/doc/worksheet.merge.spec.js b/spec/unit/doc/worksheet.merge.spec.js
@@ -212,5 +212,37 @@ describe('Worksheet', () => {
         testUtils.styles.numFmts.numFmt1
       );
     });
+
+    it('preserves merges after row inserts', function() {
+      const wb = new Excel.Workbook();
+      const ws = wb.addWorksheet('testMergeAfterInsert');
+
+      ws.addRow([1,2]);
+      ws.addRow([3,4]);
+      ws.mergeCells('A1:B2');
+      ws.insertRow(1, ['Inserted Row Text']);
+
+      const r2 = ws.getRow(2);
+      const r3 = ws.getRow(3);
+
+      let cellVals = [];
+      for (const r of [r2, r3]) {
+        for (const cell of r._cells) {
+          cellVals.push(cell._value);
+        }
+      }
+
+      let nNumberVals = 0;
+      let nMergeVals = 0;
+      for (let cellVal of cellVals) {
+          const name = cellVal.constructor.name; 
+          if (name === 'NumberValue') nNumberVals += 1;
+          if (name === 'MergeValue' && cellVal.model.master === "A2") {
+              nMergeVals += 1;
+          }
+      }
+      expect(nNumberVals).to.deep.equal(1);
+      expect(nMergeVals).to.deep.equal(3);
+    })
   });
 });