Passing array though port causes error on macOS

[AquaCash5]

Good morning, I am having a frustrating and unique issue. I am using Elm as the renderer in an electron application. Everything works fine on Linux and Windows, but on macOS, I get an error when I try and send an array through a port.

My application is a font viewer called FontFinder I made for my wife to be able to view all of the thousands of fonts on her computer. I ran into this issue when fixing the menu for macOS on branch fix-macos.

The error occurs at this point:

• main.js [107]: send “ELM-EVENT” {port: "receiveFonts", args: [...array of fonts]} to renderer.js
• renderer.js [16]: receive event call send for port “receiveFonts” and send args
• Trying to send an unexpected type of value through port “receiveFonts”: [object Object]

System:

• Mac mini (Late 2014) running macOS Big Sur 11.1

Software:

• Node 15.5.1
• npm 7.3.0
• Elm 0.19.1
• Electron 11.1.1

Recreate the issue:

• Download the repository
• git checkout fix-macos
• npm ci
• npm start
• After the application starts the error will be in the DevTools window.

Thank you for reading,
I would really appreciate some help with this issue.

[AquaCash5]

With the help of @MartinS on the Elm slack, we determined the problem lies in the list being sent to the Elm app. The list contained an undefined, causing the error.

[mattpiz]

Ports errors can be hard to solve. Sometimes one way of figuring it out is to retrieve a Json.Decode.Value directly and build a decoder for it. Then you can get better errors from the decoder.