URIs from VS Code are not always round-tripped accurately

[urbanfly]

When a new, untitled file is assigned to the Parametric Lang, the didOpen executes with params.getTextDocument().getUri() == "untitled:Untitled-1". A new TextDocumentState is created with a Java-side URI like |untitled:///:Untitled-1|.

When parse errors are reported back to VS Code, they appear in the Problems pane with a title like ":Untitled-1", but NOT as red squiggles in the open, untitled document. Clicking the problem opens a 2nd untitled document:

To Reproduce

Steps to reproduce the behavior:

1. Launch the 2nd-level VS Code
2. Load the PICO language via REPL
3. Open new untitled document
4. Set the document language to Parametric Rascal LSP
5. Any invalid program will generate parse errors in the Problems pane
   • An empty document is an invalid program
6. Click the "problem" to navigate to the document
7. A 2nd, blank "Plain Text" untitled document will open.

Expected behavior
Errors found in untitled documents (or other custom URI formats?) can be navigated to and cause red squiggles to appear.

Desktop:

• Context: VS Code w/ Rascal Metaprogramming Language 0.12.2
• DSL Extension using
  • rascal v0.40.17
  • rascal-lsp v2.21.1 (with changes from Add support for extensionless documents to the parametric language server #894)

Additional context
This appears to be related to special fallback logic in Locations.java toLoc(String uri) where the untitled:Untitled-1 URI fails with the "Opaque URI" message and is then converted to untitled:///:Untitled-1 (notice there are two colons).

I tried removing the 2nd colon, which I think is a mistake, but it doesn't solve the problem. I also tried using a single / instead of ///. None of these worked - probably because "untitlted:Untitled-1" <> "untitlted:/Untitled-1" within VS Code.

[DavyLandman]

Hi @urbanfly , thanks for the report!

Do you have to opportunity (since you're working on that #894 PR) to verify if this is also still happening on main? Since we solved quite a few of these roundtrip errors the past months.

[urbanfly]

I considered doing that, but since main doesn't even support untitled files (or files without extensions) I am not sure how to test it there.

[DavyLandman]

Is this also happening on your branch? That's close enough to main right?

Alternatively I think you might be able to trigger this bug my starting an Untitled tab and marking it as a rascal file?

[DavyLandman]

I think this might be because we don't support relative URIs in rascal. So we should think about how we map that.

[toinehartman]

Thanks for the clear reproduction case @urbanfly. I looked into this and can reproduce this on main and for the Rascal language setting as well. This is indeed caused by how we treat opaque/relative URIs, as @DavyLandman suspected. Working on a fix.