How do I know if spreadsheet cells are merged using google apps script

Question

In a Google docs spreadsheet. If cells A1 & A2 are merged, is there a way to confirm they are merged, using google apps script?

There is a merge function in GAS https://developers.google.com/apps-script/class_range#merge

But there is no function or example that shows how to check if cells are merged.

getValues etc just returns an empty string for the cell. e.g. this does not work.

function testMerge() {

  var spreadsheet = SpreadsheetApp.openById('Z3ppTjxNUE........'); 
  var sheet = spreadsheet.getSheets()[0];
  var range = sheet.getRange("A3:A4");
  var values = range.getValues();
  var formulas = range.getFormulasR1C1();
  var formulasA1 = range.getFormulas();

  range = sheet.getRange("A4");
  range.setValue("a");

  range = sheet.getRange("A3:A4");
  var values2 = range.getValues();
  var formulas2 = range.getFormulasR1C1();
  var formulasA12 = range.getFormulas();


  var count = range.getHeight();


}

Answer 1

range.isPartOfMerge()

It seems the .isPartOfMerge() method was implemented (11 sept 2016).

So you can check if a range is merged as such:

function testMerge() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheetByName("Sheet1");
  var range = sheet.getRange(1,1,2); // example for cells A1 and A2
  Logger.log(range.isPartOfMerge());
}

Docs https://developers.google.com/apps-script/reference/spreadsheet/range#ispartofmerge

---

OLD APPROACH

Posting here another approach that I like more than the accepted answer.

If you try to use GAS to store a value in a cell of a merged range, except the first cell, it will not store it.

As such, we can exploit this and attempt to store the value and check if it was stored, using a function similar to this one:

  function isMerged(range){
  try {
    range.getDataSourceUrl()
  } catch (err) {
    throw "isMerged function only works with valid GAS Range objects"
  }
  var sheet = range.getSheet();
  var rangeData = range.getValues();

  var testValue = "testing merge";

  if (rangeData.length == 1 && rangeData[0].length == 1) return false; // we have a single cell. Can't possible be merged :)

  if (rangeData.length == 1) {
    // We have a single row. Which means we're testing a row with multiple columns
    var mainCell=range.getA1Notation().split(":")[0];
    var rowNumber= sheet.getRange(mainCell).getRow();
    var nextColNumber = sheet.getRange(mainCell).getColumn()+1;
    var row = rangeData[0];
    var oldValue = row[1]; // for testing purposes, we're chosing the next possible column

    sheet.getRange(rowNumber,nextColNumber).setValue(testValue);
    if (sheet.getRange(rowNumber,nextColNumber).getValue() !== testValue) {
      return true;
    } else {
      sheet.getRange(rowNumber,nextColNumber).setValue(oldValue);
      return false;
    };
  } else if (rangeData[0].length == 1) {
    // We have multiple rows and a single column.
    var mainCell=range.getA1Notation().split(":")[0];
    var nextRowNumber= sheet.getRange(mainCell).getRow()+1;
    var colNumber = sheet.getRange(mainCell).getColumn();
    var oldValue = rangeData[1][0]; // for testing purposes, we're chosing the next possible row

    sheet.getRange(nextRowNumber,colNumber).setValue(testValue);
    if (sheet.getRange(nextRowNumber,colNumber).getValue() !== testValue) {
      return true;
    } else {
      sheet.getRange(nextRowNumber,colNumber).setValue(oldValue);
      return false;
    };
  } else {
    // We have multiple rows and multiple columns
    var mainCell=range.getA1Notation().split(":")[0];
    var nextRowNumber= sheet.getRange(mainCell).getRow()+1;
    var nextColNumber = sheet.getRange(mainCell).getColumn()+1;
    var oldValue = rangeData[1][1]; // for testing purposes, we're chosing the next possible row and next possible column

    sheet.getRange(nextRowNumber,nextColNumber).setValue(testValue);
    if (sheet.getRange(nextRowNumber,nextColNumber).getValue() !== testValue) {
      return true;
    } else {
      sheet.getRange(nextRowNumber,nextColNumber).setValue(oldValue);
      return false;
    };
  }

  // if none of these checks worked, something's fishy. Either way, return false
  return false
}

I've ran a series of quick tests and it returned true/false accordingly, but there is a limitation that I didn't have time to cover: If you had a merged range like "A1:F1" and you checked the range "A1:G1" (so, one more column), it will return true, even if G1 is not part of the merged range - because it checks only the next column using as reference the first bound row/column.