Argument and state validation utilities for Rust.

Qubit Argument provides extension traits and checking functions for validating function arguments, configuration values, indexes, ranges, and runtime state. It uses Rust's trait extension pattern for readable validation chains while returning a small structured ArgumentError.

• Readable validation: express checks close to the value being validated.
• Small error surface: use ArgumentError and ArgumentResult for all validation failures.
• Method chaining: return validated values or references so checks compose naturally.
• No panic by default: report invalid arguments through Result.
• Focused scope: provide validation utilities only, without pulling in broader common utilities.

• Zero and non-zero checks.
• Positive, negative, non-positive, and non-negative checks.
• Closed, open, left-open, and right-open range validation.
• Less-than, less-or-equal, greater-than, and greater-or-equal checks.
• Equality and inequality validation across two named arguments.

• Non-blank checks.
• Exact length, minimum length, maximum length, and range length checks.
• Regular expression match and non-match checks.
• Implementations for both str and String.

• Non-empty collection checks.
• Collection length constraints.
• Optional value presence checks.
• Conditional validation for present optional values.
• Element non-null checks for &[Option<T>].

• Boolean argument and state assertions.
• Slice-style bounds checks.
• Element index, position index, and position index range validation.

Add this to your Cargo.toml:

[dependencies]
qubit-argument = "0.3"

use qubit_argument::{
    ArgumentResult,
    NumericArgument,
    StringArgument,
};

fn validate_user(age: i32, username: &str) -> ArgumentResult<()> {
    age.require_in_closed_range("age", 0, 150)?;
    username
        .require_non_blank("username")?
        .require_length_in_range("username", 3, 20)?;
    Ok(())
}

use qubit_argument::{
    ArgumentResult,
    CollectionArgument,
};

fn validate_tags(tags: &[String]) -> ArgumentResult<&[String]> {
    tags.require_non_empty("tags")?
        .require_length_at_most("tags", 10)
}

use qubit_argument::{
    ArgumentResult,
    check_bounds,
    check_state_with_message,
};

fn read_range(offset: usize, length: usize, total: usize) -> ArgumentResult<()> {
    check_state_with_message(total > 0, "total length must be positive")?;
    check_bounds(offset, length, total)
}

• NumericArgument - numeric validation methods.
• StringArgument - string validation methods.
• CollectionArgument - collection validation methods.
• OptionArgument - optional value validation methods.

• ArgumentError - validation error with a human-readable message.
• ArgumentResult - result alias returned by validation APIs.

• check_argument, check_argument_with_message, check_argument_fmt
• check_state, check_state_with_message
• check_bounds, check_element_index, check_position_index, check_position_indexes
• require_equal, require_not_equal, require_element_non_null, require_null_or

This project maintains comprehensive test coverage for success paths, failure paths, boundary conditions, and representative type instantiations.

# Run all tests
cargo test

# Run with coverage report
./coverage.sh

# Generate text format report
./coverage.sh text

# Run CI checks (format, clippy, test, coverage, audit)
./ci-check.sh

See COVERAGE.md for detailed coverage statistics.

Runtime dependencies are intentionally small:

• regex powers regular expression validation for strings.

Copyright (c) 2025 - 2026. Haixing Hu, Qubit Co. Ltd. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

See LICENSE for the full license text.

Contributions are welcome! Please feel free to submit a Pull Request.

• Follow the Rust API guidelines.
• Maintain comprehensive test coverage.
• Document all public APIs with examples when they clarify usage.
• Run ./ci-check.sh before submitting PRs.

Haixing Hu - Qubit Co. Ltd.

More Rust libraries from Qubit are published under the qubit-ltd organization on GitHub.

Repository: https://github.com/qubit-ltd/rs-argument