Theia: firefox: application fails to load

[vince-fugnitto]

Bug Description:

The application fails to load on firefox.
The loading screen is displayed, and there is an error on startup:

It would be good for others to confirm that it is broken as well.

Steps to Reproduce:

1. start the example-brower application (yarn start:browser)
2. open localhost on firefox

Additional Information

• Operating System: macOS
• Theia Version: 7cf845b

[kittaakos]

It would be good for others to confirm that it is broken as well.

Confirmed.

[kittaakos]

I have seen this before, not all the browsers(?) allow positive lookahead groups for regexp, it's an ES7 thing (I am just guessing, though). I have seen lookahead groups commit recently, not sure where.

[kittaakos]

Here, FF and IE does not support groups, I remember I had the same issue a year ago.

[vince-fugnitto]

@kittaakos this is what I could find that was added recently (following #7105):

https://github.com/eclipse-theia/theia/blob/7cf845b389780846bf727f6ef914d97b6f16d368/packages/preferences/src/browser/util/preference-tree-generator.ts#L72

https://github.com/eclipse-theia/theia/blob/7cf845b389780846bf727f6ef914d97b6f16d368/packages/preferences/src/browser/util/preference-tree-generator.ts#L103

I'll try a commit before and see if the changes affected firefox.

[vince-fugnitto]

@kittaakos this is what I could find that was added recently (following #7105):

https://github.com/eclipse-theia/theia/blob/7cf845b389780846bf727f6ef914d97b6f16d368/packages/preferences/src/browser/util/preference-tree-generator.ts#L72

https://github.com/eclipse-theia/theia/blob/7cf845b389780846bf727f6ef914d97b6f16d368/packages/preferences/src/browser/util/preference-tree-generator.ts#L103

I'll try a commit before and see if the changes affected firefox.

I confirmed that a commit before the problem was not there, we will need to update the regular expressions.

[akosyakov]

@vince-fugnitto Do you take care about it?

[akosyakov]

I wonder is there some es linting for regex that we use only syntax supported by all browsers.