RustCop

An experimental Rust style linter and formatter inspired by C#'s StyleCop.

RustCop checks and auto-fixes style violations in your Rust source files, starting with import statement formatting.

Installation

cargo install rustcop

Usage

Check for violations

cargo rustcop check [paths...]

Scans .rs files and reports style violations without modifying anything. Exits with code 1 if any diagnostics are found.

Auto-fix violations

cargo rustcop fix [paths...]

Fixes violations in-place and runs a verification pass to confirm everything is clean.

If no paths are given, both commands default to the current directory.

Options

Flag	Description
`-c`, `--config <FILE>`	Path to the config file (default: `rustcop.toml`)

Configuration

Create a rustcop.toml in your project root:

version = 1

# When true, warnings are treated as errors (default: false)
treat_warnings_as_errors = false

# When true, suppression directives must include justifications (default: true)
require_suppression_justification = true

[imports]
enabled = true
group = true    # Group imports: std → external → crate/self/super
sort = true     # Sort imports alphabetically within each group
merge = true    # Merge imports from the same crate into one `use` block

Suppression Directives

RustCop supports both comment-based and attribute-based suppression directives, similar to C#'s [SuppressMessage].

Comment-Based Suppressions

// Suppress all rules for the entire file
// rustcop:ignore-file

// Suppress all rules for the next line
// rustcop:ignore
fn my_function() { }

// Suppress a specific rule with justification (recommended)
// rustcop:ignore RC1001: Legacy code, will refactor in v2.0
fn another_function() { }

// Suppress multiple rules with a shared justification
// rustcop:ignore RC1001, RC1002: Performance critical section
fn performance_function() { }

// Stack multiple suppressions for different justifications per rule
// rustcop:ignore RC1001: Reason for RC1001
// rustcop:ignore RC1002: Reason for RC1002
fn complex_function() { }

Attribute-Based Suppressions

// Suppress all rules for a function
#[rustcop::ignore]
fn my_function() { }

// Suppress a specific rule with justification
#[rustcop::ignore(RC1001, justification = "Legacy API compatibility")]
fn another_function() { }

// Stack multiple attributes for different justifications per rule
#[rustcop::ignore(RC1001, justification = "Performance optimization")]
#[rustcop::ignore(RC1002, justification = "Required for backwards compatibility")]
fn complex_function() { }

// Suppress at module level
#![rustcop::ignore]

The attribute macro is re-exported from the main rustcop crate:

use rustcop::ignore;

#[rustcop::ignore]
fn my_function() { }

See examples/suppression_demo.rs for more examples.

Structured Output

RustCop can output diagnostics in machine-readable formats:

# Generate SARIF output
cargo rustcop check --out results.sarif

# Generate JSON output
cargo rustcop check --out results.json

The format is automatically detected from the file extension. SARIF v2.1.0 is supported.

Rules

ID	Name	Description
RC1001	ImportFormatting	Groups, sorts, and merges `use` statements
RC2001	DisallowSuperImports	Reports use of `super::` imports when configured
RC9001	UnusedSuppression	Reports suppression directives that don't suppress any diagnostics
RC9002	MissingSuppressionJustification	Reports suppressions without justifications when `require_suppression_justification = true`

Import formatting follows rustfmt conventions:

Grouping — standard library first, then third-party crates, then internal (crate/self/super), separated by blank lines.
Sorting — alphabetical within each group.
Merging — multiple imports from the same crate are combined into a single use block.
Multi-line expansion — imports with nested braces are expanded to one item per line.

Unused Suppression Detection: RustCop generates an error (RC9001) for any suppression directive that doesn't actually suppress any diagnostics. This helps keep your codebase clean by detecting:

Suppressions added for issues that have since been fixed
Suppressions targeting the wrong line or rule
Suppressions for rules that don't exist or aren't enabled

Suppression Justification Enforcement: When require_suppression_justification = true in your config, RustCop generates an error (RC9002) for any suppression that lacks a justification comment. This helps maintain documentation of why rules are being suppressed.

Super Import Validation: When [lints.disallow_super_imports] is configured with severity = "error", RustCop generates an error (RC2001) for any use of super:: imports. This can be useful for enforcing explicit import paths.

License

Licensed under either of

at your option.

rustcop 0.1.5