TypeError: Cannot read property 'set' of undefined

[bpasero]

I started on a fresh insiders opening a first folder, then added a second folder. Then I saved the workspace and hit refresh:

ERR Cannot read property 'set' of undefined: TypeError: Cannot read property 'set' of undefined
    at e.addChild (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:2409:129)
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:4694:92
    at Array.forEach (native)
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:4694:70
    at Object.g [as _notify] (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:146:729)
    at Object.enter (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:150:61)
    at n.Class.derive._creator._run (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:151:866)
    at n.Class.derive._creator._completed (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:151:307)
    at Object.g [as _notify] (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:146:729)
    at Object.enter (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:150:61)
    at n.Class.derive._oncancel._run (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:151:866)
    at n.Class.derive._oncancel._completed (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:151:307)
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:2945:168
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:2946:31
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:265:204
    at Function.<anonymous> (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:2946:4)
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:264:833
    at s (file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:264:364)
    at file:///Applications/Visual Studio Code - Insiders.app/Contents/Resources/app/out/vs/workbench/workbench.main.js:264:468
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickCallback (internal/process/next_tick.js:104:9)

Seems to be somewhere here:

[isidorn]

@bpasero I could not repro following your steps, however looking at the code we have null guards for this.chidlren for all methods.
For now I decided to handle the case when somebody is adding children to a ExplorerItem that is not yet fully initialised to make this ExplorerItem a directory, thus initalizing the children array.
An alternative would be to ignore the add but in that case we could loose some children.

[bpasero]

I tried to reproduce and cannot. I hope you know what you are doing with that change in the explorer model, I did not verify if that breaks anything...

[isidorn]

@bpasero thanks, if it breaks something I think we will see in insiders. Though it can break only already broken beahvior (trying to add children to a non folder)