File: Project Index — RuboCop master

Note	The project index feature was introduced in RuboCop 1.87.

Warning

This feature is experimental and should not be considered stable. Changes to its behavior or interface may occur.

RuboCop can optionally use Rubydex to build a project-wide index of declarations and references. When enabled, cops that opt in can consult the index to detect issues that span multiple files.

This integration is opt-in and experimental. The default behavior of RuboCop is unchanged.

Enabling

Add rubydex to your Gemfile and bundle install:
```
gem 'rubydex', require: false
```
Set the flag in your .rubocop.yml:
```
AllCops:
  UseProjectIndex: true
```

If UseProjectIndex is true but the rubydex gem is not installed, or the running Ruby is older than the version rubydex supports, RuboCop prints a warning and falls back to its standard file-local behavior.

The integration requires Ruby 3.2 or later. On Ruby 3.1 and older, AllCops/UseProjectIndex has no effect even if set to true.

What it enables

Lint/ConstantReassignment reports reassignments whose previous definition lives in another file. For example:

# a.rb
CROSS_FILE_CONST = :first

# b.rb
CROSS_FILE_CONST = :second

With UseProjectIndex: true, RuboCop reports a Lint/ConstantReassignment offense referencing the other file. Index-aware cops automatically pick up the index whenever it is built; no per-cop opt-in is required.

Notes

rubydex requires Ruby 3.2 or newer and ships native (Rust) extensions.
Parallel inspection is currently disabled on Windows when UseProjectIndex is on; use serial inspection (omit --parallel).
The index is rebuilt once per rubocop invocation; no on-disk index is shared between runs.