Ghostbuster

Ghostbuster finds dead Python code without starting Python. It is a Rust command-line tool built directly on Ruff's parser, syntax tree, source ranges, and line index.

The project takes Vulture's practical dead-code model as its behavioral reference while keeping a small Rust-native interface and a slightly more precise distinction between normal names and object members.

Install

With a prebuilt binary from a tagged GitHub release, or from PyPI under the ghostbuster-code distribution name:

uv tool install ghostbuster-code

The PyPI name is longer because the unrelated ghostbuster name was already taken. Both methods install the same ghostbuster executable and do not require Python at runtime. To build the full source checkout instead:

cargo install --git https://github.com/mazdak/ghostbuster --locked

Try it

cargo run -- src tests

Example output:

src/example.py:8: V103 unused function 'retired_handler' (60% confidence)
src/example.py:13: V201 unreachable code after 'return' (100% confidence)

Useful options:

ghostbuster --min-confidence 80 src
ghostbuster --exclude 'generated/**,vendor/**' .
ghostbuster --ignore-names 'visit_*,legacy_hook' src
ghostbuster --ignore-decorators '@app.route,@registry.*' src
ghostbuster --format json src > findings.json

Run ghostbuster --help for the complete interface. Explicit files are accepted regardless of their extension. Directories are walked recursively for .py files while respecting Git and standard ignore files.

Exit codes are designed for CI:

Findings

Ghostbuster understands definitions and loads across all input files in one run. It also handles common dynamic-Python signals such as __all__, getattr, hasattr, decorators, properties, dunder conventions, pytest entry points, type comments, dynamic format strings, Vulture's packaged protocol whitelists, and # noqa comments. Source files support Python's UTF-8 BOM plus common PEP 263 encodings, including Latin-1, Macintosh encodings, and numeric cpNNN code pages. F401 suppresses V104 and F841 suppresses V107, so existing Ruff suppressions remain useful.

Reachability covers dead tails after return, raise, break, and continue; constant branches; non-terminating while loops; terminal if, try, and exhaustive match branches; and nested suites. Ruff's AST truthiness handles literals, with Vulture-compatible short-circuit evaluation for constant and, or, and not expressions.

Why Ruff rather than a new parser?

Python syntax evolves quickly and source positions are easy to get subtly wrong. Ghostbuster uses the same Rust crates as Ruff and ty for parsing, AST traversal, UTF-8 byte ranges, Unicode columns, CRLF lines, and BOM handling. The five required crates are checked into vendor/ruff and pinned to one upstream Git revision, so builds do not silently switch parser implementations.

Ghostbuster itself only implements the dead-code policy that those projects do not expose as a standalone public API. Pulling in ty's full database, module resolver, and type checker would make a simple scanner much larger without replacing that policy layer.

Vulture compatibility evaluation

The data-driven corpus in tests/vulture is derived from Vulture's upstream tests and pins the exact source revision. It contains 46 cases: eight compare the complete result and collectively cover V101–V107 plus V201; the other 38 project one diagnostic category so a focused reachability test does not fail because an unrelated function in its snippet is also unused.

Ghostbuster deliberately preserves Vulture's project-wide bare-name behavior, which keeps the compatibility oracle stable across modules. Its precision improvement is narrower: normal names and object members live in separate namespaces, so a bare function call does not automatically mark every same-named method alive. Intentional differences are documented separately from missing compatibility behavior.

Development

Ghostbuster pins the same Rust 1.97 toolchain currently used by Ruff. The required checks are:

cargo fmt --all -- --check
cargo clippy --workspace --all-targets --all-features -- -D warnings
cargo test --workspace --all-targets --all-features
cargo check --workspace --all-targets --all-features --locked --offline

The minimum supported Rust version is 1.95. The pinned 1.97 toolchain supplies the formatter and Clippy version used by CI. See CONTRIBUTING.md for the complete development workflow.

• Ruff source revision: f34ad603f07c766f9c4941a2f23ae88c84812c93
• Vulture source revision: 2c21cb0ae2afa657e36f6a397cb573608a65d79e

Ghostbuster is intentionally not a crates.io package: its Ruff internals are pinned path dependencies. Build or install it from a complete source checkout, use the platform wheels on PyPI, or download a native release archive.

License

Ghostbuster is MIT licensed. Vendored Ruff code and Vulture-derived test data retain their upstream MIT notices. See THIRD_PARTY.md for provenance and THIRD_PARTY.html for the complete generated dependency notices shipped with releases.