set default value of colorTheme and iconTheme preference

[akosyakov]

What it does

fix #8374: make sure that color and icon themes are having default values.

Python extension reads these values to generate theme for a webview. If they are missing then dark is used what is happening here #8374 (comment)

How to test

• install python extension from the open vsxk
• create a new notebook
• check that highlighting in notebook matches to the current theme
  • there can be a bit of a delay, python extension needs to create json file with theme and load it in the webview to apply
• check that logs don't have errors about undefined theme
• change the heme, check that theme is eventually is applied
  • again here can be delay required on theme regeneration by the extension
• reload the page and observe that loading screen as well as shell never flickes between default dark theme and one which you selected before
• try again to create a notebook and check that theme is proper

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

[akosyakov]

tests are failing now, I will have a look

[akosyakov]

@kittaakos I've addressed your comments and fixed tests.

[vince-fugnitto]

I'll perform a functional review shortly.

[kittaakos]

I've addressed your comments and fixed tests.

Nice, I checked the code, it looks good, now I am going to verify it with the Python extension as suggested.

[kittaakos]

I see a lot of errors in the console:

f JSON input
    at JSON.parse (<anonymous>)
    at /Users/akos.kitta/git/theia/node_modules/jsonfile/index.js:33:18
    at /Users/akos.kitta/git/theia/node_modules/graceful-fs/graceful-fs.js:115:16
    at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:61:3)
root ERROR Failed to parse data from " /Users/akos.kitta/.theia/plugin-storage/global-state.json ". Reason: SyntaxError: /Users/akos.kitta/.theia/plugin-storage/global-state.json: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at /Users/akos.kitta/git/theia/node_modules/jsonfile/index.js:33:18
    at /Users/akos.kitta/git/theia/node_modules/graceful-fs/graceful-fs.js:115:16
    at FSReqCallback.readFileAfterClose [as oncomplete] (internal/fs/read_file_context.js:61:3)
root ERROR Failed to parse data from " /Users/akos.kitta/.theia/plugin-storage/global-state.json ". Reason: SyntaxError: /Users/akos.kitta/.theia/plugin-storage/global-state.json: Unexpected end of JSON input

I am not sure if it is related to the theme changes or nor; probably not.

[kittaakos]

I evaluated (Ctrl+Enter) println('123') and got this as an error. It's OK to see the error, I do not have the required Python 3.x interpreter, but it's not good that I cannot copy the stack trace. 😕

[kittaakos]

I have verified it locally with the electron example. The changeset looks good, the app works well. Thank you! 👍

[akosyakov]

@kittaakos I don't think an exception related to changes. I've opened a follow-up issue: #8384