[editor] Error when doing an undo with Ctrl/Cmd+Z in a JSON editor

[kittaakos]

This happens on the branch GH-1479. My WS root is theia. Open the lerna.json in the WS root, edit it, undo it with Ctrl/Cmd+Z:

16:47:20.070 editor.main.js:31 Uncaught (in promise) TypeError: this._state.then is not a function
    at n.Class.derive._creator.then (editor.main.js:31)
then @ editor.main.js:31
Promise.then (async)
step @ monaco-outline-contribution.ts:6
(anonymous) @ monaco-outline-contribution.ts:6
__awaiter @ monaco-outline-contribution.ts:6
(anonymous) @ monaco-outline-contribution.ts:89
o @ editor.main.js:31
t._emitEvents @ editor.main.js:31
e._emitCollected @ editor.main.js:31
e.endDeferredEmit @ editor.main.js:31
t.undo @ editor.main.js:31
t.trigger @ editor.main.js:31
execute @ monaco-command.ts:137
MonacoCommandRegistry.execute @ monaco-command-registry.ts:60
execute @ monaco-command-registry.ts:50
KeybindingRegistry.tryKeybindingExecution @ keybinding.ts:372
KeybindingRegistry.run @ keybinding.ts:406
(anonymous) @ frontend-application.ts:98

Interestingly, this happens only, when you are trying to undo at least two characters long modification. The undo succeeds, by the way.

[kittaakos]

It seems to happen only if we are undoing some (2-* characters) deletion.

[kittaakos]

It also happens in the CSS editor, but for instance, not in a JS editor.

[kittaakos]

It does not happen in the HTML editor. (Unlike the CSS and the JSON editor, the HTML one does not provide code completion and CA though.)

[kittaakos]

I hit another error when I was trying to figure out the cause of the original issue:

Error: Canceled
    at Object.enter (winjs.base.raw.js:824)
    at Promise_ctor._run (winjs.base.raw.js:1068)
    at Promise_ctor.cancel (winjs.base.raw.js:964)
    at Object.enter (winjs.base.raw.js:782)
    at _Base.Class.derive._creator._run (winjs.base.raw.js:1068)
    at _Base.Class.derive._creator.cancel (winjs.base.raw.js:964)
    at _Base.Class.derive._creator._cancelAction (winjs.base.raw.js:1311)
    at Object.enter (winjs.base.raw.js:805)
    at _Base.Class.derive._creator._run (winjs.base.raw.js:1068)
    at _Base.Class.derive._creator.cancel (winjs.base.raw.js:964)

I am not sure if that is a real issue or the expected way to handle cancelations, but it would be nice not to show this in the console.

[kittaakos]

I have tried to reproduce this issue outside of Theia by cloning the examples from here, I have set the monaco-editor version to 0.10.1 and the languages to json, just like in Theia. The error does not happen.

[kittaakos]

I can confirm, it happens when autoSave is off. We need to revisit this issue once the monaco-editor and monaco-languages have been updated.

[kittaakos]

Ref: #1539.

[akosyakov]

@kittaakos Can you reproduce it against #7481?