Error running diagnostics: index 0 out of array bounds: 0...0

[maxnotarangelo]

Description

Ruby LSP Information

VS Code Version

1.96.2

Ruby LSP Extension Version

0.9.7

Ruby LSP Server Version

0.23.11

Ruby LSP Add-ons

• Ruby LSP Rails

Ruby Version

3.3.5

Ruby Version Manager

rbenv

Installed Extensions

Click to expand

• change-case (1.0.0)
• debugpy (2024.6.0)
• dotenv (1.0.1)
• even-better-toml (0.21.2)
• gc-excelviewer (4.2.63)
• gitlens (16.3.2)
• haml (1.4.1)
• implicit-parentheses (1.1.0)
• isort (2023.10.1)
• prettier-vscode (11.0.0)
• pyright (1.1.327)
• rewrap (1.16.3)
• rubocop-quick-fix (0.3.1)
• ruby-lsp (0.9.7)
• ruby-rstfilter (0.0.4)
• svg-preview (2.8.3)
• terraform (2.34.3)
• vscode-apollo (2.5.5)
• vscode-coverage-gutters (2.13.0)
• vscode-erb-beautify (0.5.0)
• vscode-eslint (3.0.10)
• vscode-github-actions (0.27.1)
• vscode-pylance (2025.2.1)
• vscode-rdbg (0.2.2)
• vscode-scss (0.10.0)
• vscode-stylelint (1.4.0)
• vscode-syntax-tree (0.5.1)
• vscode-yaml (1.16.0)
• vsliveshare (1.0.5948)

Ruby LSP Settings

Click to expand

Workspace

{
  "enabledFeatures": {
    "codeActions": true,
    "diagnostics": true,
    "documentHighlights": true,
    "documentLink": true,
    "documentSymbols": true,
    "foldingRanges": true,
    "formatting": true,
    "hover": true,
    "inlayHint": true,
    "onTypeFormatting": true,
    "selectionRanges": true,
    "semanticHighlighting": true,
    "completion": true,
    "codeLens": true,
    "definition": true,
    "workspaceSymbol": true,
    "signatureHelp": true,
    "typeHierarchy": true,
    "references": true
  },
  "rubyVersionManager": {
    "identifier": "rbenv"
  },
  "formatter": "rubocop"
}

User

{
  "enabledFeatures": {
    "codeActions": true,
    "diagnostics": true,
    "documentHighlights": true,
    "documentLink": true,
    "documentSymbols": true,
    "foldingRanges": true,
    "formatting": true,
    "hover": true,
    "inlayHint": true,
    "onTypeFormatting": true,
    "selectionRanges": true,
    "semanticHighlighting": true,
    "completion": true,
    "codeLens": true,
    "definition": true,
    "workspaceSymbol": true,
    "signatureHelp": true,
    "typeHierarchy": true,
    "references": true
  },
  "featuresConfiguration": {},
  "addonSettings": {},
  "rubyVersionManager": {
    "identifier": "rbenv"
  },
  "customRubyCommand": "",
  "formatter": "rubocop",
  "linters": null,
  "bundleGemfile": "",
  "testTimeout": 30,
  "branch": "",
  "pullDiagnosticsOn": "both",
  "useBundlerCompose": false,
  "bypassTypechecker": false,
  "rubyExecutablePath": "",
  "indexing": {},
  "erbSupport": true,
  "featureFlags": {
    "all": true
  },
  "sigOpacityLevel": "1"
}

Also, I'm using Cursor, which is a clone of VS Code. I'm guessing that's not the cause of the issue, but wanted to flag that just in case.

Reproduction steps

1. Restart Ruby LSP
2. Wait for it to finish initializing

The following warning pops up:

Error running diagnostics: index 0 outside of array bounds: 0...0

I tried restarting Ruby LSP with the output open. Here are the last four lines:

2025-03-01 09:52:57.846 [info] (myproject) Finished initializing Ruby LSP!
2025-03-01 09:53:24.221 [info] (myproject) Activating Ruby LSP Rails add-on v0.4.0
2025-03-01 09:53:24.226 [info] (myproject) Ruby LSP Rails booting server
2025-03-01 09:53:26.975 [info] (myproject) Finished booting Ruby LSP Rails server

The warning pops up after the Ruby LSP Rails booting server line.

Severity

It's not clear that this is breaking any functionality; syntax highlighting and format-on-save are still working for me. So this may not be very urgent to fix.

[vinistock]

Thank you for the report! Diagnostics is mostly about the integrations with linters, so the issue might be coming from another gem.

What linter are you using? RuboCop? And is that up to date?

Also, I assume that happens in the middle of typing, while the code is in an intermediate state. Were you able to detect what code pattern triggers this?

[maxnotarangelo]

Yes, using rubocop v1.57.1.

I was seeing it when I had a bunch of files (including ruby files) open, but it would happen even when the active files (i.e. the ones in the foreground in the editor) were not ruby files. When I restarted Ruby LSP in this state, it wouldn't print any lines in the output like the following:

2025-03-03 16:26:43.087 [info] (myproject) Determined that document should be indexed: file:///path/to/file/in/project.rb

which made me think it wasn't related to that.

But I just restarted vscode, closed all my files, and now I can't get the warning to pop up any more. I'll let you know if I see it again, if I figure out how to reproduce it more reliably, or if I figure out what's actually causing it.

And let me know if there's any more info I can provide to help debug this.

[andyw8]

This seems different from RuboCop failures we're seen in the past. Normally we'd expect to see this text as part of the error message.

@vinistock we could change the rescue to log the backtrace with send_log_message.