Completion invocation not always calling completionFor

[nametable]

When completion is invoked, the relevant completionFor function is not always being called. Something appears to be wrong with the next features computation or the CompletionParser. It is also possible that I have a misunderstanding of how completions are supposed to work. See some screenshots below, relating to the reproduction steps:

Completions working

Completions not working

Langium version: main
Package name: langium

Steps To Reproduce

1. Checkout completion-issue-repro from my fork of Langium - https://github.com/nametable/langium/tree/completion-issue-repro
2. Build the DomainModel example
3. Run the extension for DomainModel example
4. Open blog.dmodel
5. Trigger completion inside of string literals within [Attribute2("")] with Ctrl+Space
6. See that completion works for the top Attribute2 but not the bottom Attribute2.

Link to code example:

https://github.com/nametable/langium/tree/completion-issue-repro

The current behavior

The completion provider is not invoked for the lower Attribute2 annotation, while it is for the upper.

The expected behavior

Both Attribute2 string literals should have working completion.

[msujew]

Looks like something is going wrong in the token interpreter that we use to identify the current position. See here. I'll take a look at this soon. Thank you for the reproducible report :)