LSP crashes on didOpen for non-file URIs (mendix-mdl: scheme)

[kaspergff]

Summary
mxcli lsp --stdio panics when the client opens a document whose URI scheme is not file:. The VS Code MDL extension opens virtual documents with the mendix-mdl: scheme. Each open crashes the server. VS Code restarts it, the document is reopened, and the server crashes again. After 5 crashes in 3 minutes, VS Code stops restarting the server.

Environment

• MDL extension build: nightly-20260927-95091765 (2026-09-27T08:03:28Z)
• OS: Windows 11 Enterprise 10.0.26200
• Server command: mxcli lsp --stdio

Steps to reproduce

1. Open a Mendix project folder in VS Code with the MDL extension active.
2. Open a virtual document with the mendix-mdl: scheme, for example an extension preview or a describe view.
3. The language server crashes.

Actual result

panic: only file URIs are supported, got mendix-mdl

go.lsp.dev/uri.URI.Filename(...)
	go.lsp.dev/uri@v0.3.0/uri.go:52
main.checkableDocument(...)
	github.com/mendixlabs/mxcli/cmd/mxcli/lsp_diagnostics.go:32
main.(*mdlServer).publishDiagnostics(...)
	github.com/mendixlabs/mxcli/cmd/mxcli/lsp_diagnostics.go:104
main.(*mdlServer).DidOpen(...)
	github.com/mendixlabs/mxcli/cmd/mxcli/lsp_diagnostics.go:128

The server exits with code 2. VS Code then reports: "The MDL Language Server server crashed 5 times in the last 3 minutes. The server will not be restarted."

Expected result
The server ignores non-file documents for file-based diagnostics, or handles them in memory. It must not crash.

Suggested fix
In checkableDocument (lsp_diagnostics.go:32), check uri.Scheme before calling uri.Filename(). Return early when the scheme is not file. Other handlers that call Filename() probably need the same guard.

Workaround
Close all mendix-mdl: tabs and reload the VS Code window.

[github-actions]

Issue Triage

Summary
The mxcli language server panics and exits when it receives a didOpen notification for a document whose URI scheme is not file: (e.g., mendix-mdl: virtual documents).

Checklist of required bug‑report information

Required info	Present?	Notes
mxcli version (output of mxcli --version or commit/build)	❌	Not mentioned
Mendix version of the project (e.g., 10.x, 9.x)	❌	Not mentioned
Scenario – what the user was trying to do	✅	Opening a Mendix project in VS Code with the MDL extension and opening a virtual document
Expected output – what should have happened	✅	Server should ignore or handle non‑file documents without crashing
Experienced output – what actually happened (error, crash)	✅	Panic stack trace and server exit code 2
AI bug report – output of mxcli diag --bundle or session log	❌	Not provided

What’s missing
To help us reproduce and fix the issue, could you please add:

1. The version of mxcli you’re running (mxcli --version or the commit/build identifier).
2. The Mendix version of the project you’re working with (e.g., 10.6, 9.24).
3. If possible, a diagnostic bundle (mxcli diag --bundle) or at least the relevant session log from the crash.

Once we have those details, we’ll be able to investigate further. Thanks for reporting this!

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Automated triage via OpenRouter — workflow source

[ako]

Thanks for reporting this. It's fixed on main (f6f3956, synced in #1259): the language server no longer crashes on didOpen for a non-file URI. The fix is ako#919, with a regression test. Closing; if you still see it with a build from today or later, please reopen with a reproduction.