Selecting Intellisense suggestion results in doubled content being typed

[jasonwilliams]

Raised from: styled-components/vscode-styled-components#325

@mjbvz do you have any idea where to look for debugging the below? I've been trawling through the typescript-styled-plugin code and don't see anything obvious. Do you have any tips on how to fix this?

It looks like it doesn't replace what's already there and only inserts instead. The issue though is we haven't changed anything in this plugin apart from maybe updated CSS lang server dependency.

Describe the bug (including copyable syntax)
I see this as a one solid issue, symptoms of which are being solved in other issues. This is a continuation of this styled-components/vscode-styled-components#219.
Namely, the Intellisense in styled-components code won't account for previously typed text when making suggestions and completions. I will describe it in several examples below.

1. Start creating some pseudo styling like after, selection, etc.
   
   After hitting ENTER you will get this
   

2. If you start typing some css, Intellisense box would pop-up, close it and continue typing again. Say, it was flex- before. After applying the suggested option, say, flow, you will get flex-flex-flow (so the previously typed text is not accounted).

This is happening to me since early versions (below 1.0) of the extension.

Expected behavior
The behavior should be identical with regular css files.

Build environment (please complete the following information):

• OS: ubuntu 18.04 or windows 10, both using the same versions of vscode and extension.
• [email protected]
• [email protected] (or other versions, does not matter)

[jasonwilliams]

I've tested this behaviour in an old version of typescript-styled-plugin 9769232 and it still happens. So i don't think its a regression