github / github/codeql

CodeQL Ruby parser fails on bare & block forwarding in multi-line method calls

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bug question
Dominant language
CodeQL
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Description

# 🖼️ Context

CodeQL's Ruby parser encounters parse errors when using Ruby 3.1+'s anonymous block forwarding syntax (&) in specific contexts, despite this being valid Ruby syntax.

## Reproduction Case

```ruby
module TestCase
def method_with_bare_ampersand(&)
some_method_call(
keyword_arg1: "value1",
keyword_arg2: "value2",
keyword_arg3: "value3",
& # <-- CodeQL parse error occurs here
)
end

# This works fine - single line call
def working_method(&)
simple_call(&)
end

private

def some_method_call(keyword_arg1:, keyword_arg2:, keyword_arg3:, &block)
yield if block_given?
end

def simple_call(&block)
yield if block_given?
end
end
```

### Environment
- Repo: [rubygems/rubygems.org](https://github.com/rubygems/rubygems.org)
- recent [workflow run](https://github.com/rubygems/rubygems.org/actions/runs/17104368086/job/48509269173?pr=5925))
- [offending file](https://github.com/rubygems/rubygems.org/blob/ae3f654e67d74122a692de4e7832fa6657d98a7a/app/controllers/concerns/avo_auditable.rb#L26)
- [offending file](https://github.com/rubygems/rubygems.org/blob/ae3f654e67d74122a692de4e7832fa6657d98a7a/app/controllers/concerns/maintenance_tasks_auditable.rb#L26)
- CodeQL CLI version: 2.15.5
- Ruby version: 3.4.x
- Syntax: Valid Ruby (confirmed with ruby -c)

### 📝 Notes

- The issue only occurs with multi-line method calls where & appears on its own line
- Single-line calls with & work correctly
- Named block parameters (e.g., &block) work in all contexts
- This is valid Ruby 3.1+ anonymous block forwarding syntax

### Impact

This prevents CodeQL security analysis on codebases using modern Ruby block forwarding patterns, forcing developers to use less idiomatic code or exclude files from analysis.

Contributor guide

Open the contributing guide

Research direction

Start by reproducing CodeQL analysis against app/controllers/concerns/avo_auditable.rb and app/controllers/concerns/maintenance_tasks_auditable.rb, then compare the result with ruby -c and the supplied reproduction. Done means the CodeQL Ruby parser accepts anonymous block forwarding on its own line in a multi-line call and analysis proceeds without a parse error.

Written by the indexing model from the issue text.

Assessment

Tech stack
ruby
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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