Google Apps Script - HTML service “createTemplateFromFile” not usable from within App (spreadsheet, etc.)?

Question

The docs for HtmlService don\'t state that this shouldn\'t work, but it seems that the template approach is limited to web app Apps Script projects.

I am attempting

Answer 1

It seems you haven't gone through the documentation in detail. Please, look at the reference documentation of class HtmlTemplate.

Answer 2

You need to evaluate() a template to create an HtmlOutput object.

function showSidebar(){

  var html = HtmlService.createTemplateFromFile('changeDialog');

  var a = "test";

    SpreadsheetApp.getUi() 
      .showSidebar(html.evaluate());
                        //////////
}

Since your changeDialog.html file contains no template tags, you could instead create an HTML file from it directly:

function showSidebar(){

  var html = HtmlService.createOutputFromFile('changeDialog');
                               //////

  var a = "test";

    SpreadsheetApp.getUi() 
      .showSidebar(html);
}