Q. I am trying to submit an app to the 21.co marketplace via 21 publish submit and I am getting an error message saying “invalid YAML”.
A. You can validate your YAML using the online editor at editor.swagger.io or using YAMLlint at www.yamllint.com. Most of the problems that I have encountered have to do with single and double quoting as explained here and here and here. One particular tip is that you do not escape the single quote character by using \’ , instead you escape it using the single quote character, i.e. ”. What I usually do is take a working manifest.yaml file from one of the 21.co/learn tutorials and then carefully edit the text I want, leaving the existing quotation marks intact.