Getting Started

Version 0: expect changes

While the crate is at version 0.x:

• The split into modules, and so into Cargo features, may change. A helper can move to another module — and so to another feature to enable — from one release to the next.
• The code and security verification will keep improving. More checks (fuzzing and static analysis, for instance) are planned, and each helper’s page says what it guarantees and what it does not.

Pin the exact version and read the changelog before upgrading.

Installation

cargo add helpers4

That enables every module. Each module is a Cargo feature of the same name, so to take only some of them, turn the default features off and name the ones you want:

cargo add helpers4 --no-default-features --features string,hex

Every module page shows the command for its feature and the matching Cargo.toml line with the current version. The crate is pre-1.0: pin the exact version and read the changelog before upgrading.

Quick Start

Import through the module path:

use helpers4::array::{group_by, unique};
use helpers4::hex;
use helpers4::string::{slugify, truncate};

assert_eq!(slugify("Hello, World!"), "hello-world");
assert_eq!(truncate("A very long title", 10, "..."), "A very ...");
assert_eq!(unique(&[1, 2, 1, 3, 2]), vec![1, 2, 3]);
assert_eq!(hex::encode(&[0xde, 0xad, 0xbe, 0xef]), "deadbeef");

let by_parity = group_by(&[1, 2, 3, 4, 5], |n| n % 2 == 0);
assert_eq!(by_parity[&true], vec![2, 4]);

Helpers take borrowed data (&str, slices) and return new values: nothing is mutated unless the documentation says so.

Errors

A helper that can fail returns a Result with an error enum you can match on, never a bare bool that hides the reason:

use helpers4::hex::{decode, DecodeError};
use helpers4::net::{is_valid_hostname, HostnameError};

assert_eq!(decode("abc"), Err(DecodeError::OddLength));
assert_eq!(is_valid_hostname("-bad.example"), Err(HostnameError::HyphenEdge));

Error enums are #[non_exhaustive]: new variants can be added without breaking your match, so keep a wildcard arm.

Names and imports

Names repeat across modules on purpose, so always import through the module path rather than glob-importing a module (use helpers4::string::*; would make the next name collision your problem). When two helpers from different modules share a name, rename at the import site with as, suffixing the module name so the origin stays visible:

use helpers4::string::truncate as truncate_string;

See Names and imports for the list of names that exist in more than one module.

Explicit inputs

Nothing reads the time or the process environment behind your back:

• cache::ExpiringMap takes now as an argument, so it is trivially testable and works with unix seconds, milliseconds or an Instant.
• env works on the text of a .env file, not on the process: you read the file, edit the content, and write it back.
• time::unix_now is fallible: a clock set before 1970 is an error, not a silent 0 (which would make every expiry look valid).

Platforms

Target	Support	Notes
Linux, macOS, Windows	✅	Tested in CI on stable, beta and the minimum supported Rust version
wasm32-unknown-unknown, wasm32-wasip1	✅ builds	Checked to compile; not run there. time::unix_now needs a clock, which wasm32-unknown-unknown does not have
no_std	❌	The crate uses std

The minimum supported Rust version is shown on the modules overview.

Quality Standards

Every helper ships with:

• 100% code coverage (lines, functions and regions), enforced in CI
• Unit tests next to the implementation, and property-based tests (proptest): invariants checked against thousands of random inputs
• Doc tests — every example on the module pages is a test that runs on each change
• Mutation testing (cargo-mutants) — tests are checked to catch regressions, not just to execute the code
• Benchmarks (criterion) where speed matters, compared with the base branch on every pull request
• Lints — clippy in pedantic mode with unwrap, expect and panic denied outside tests, and unsafe forbidden
• Dependency and license audit (cargo-deny) on every pull request and release
• Traceable releases — published from CI with short-lived credentials (crates.io trusted publishing), with a build provenance attestation attached to each GitHub release

Next Steps

• Browse the Modules
• Read the Philosophy
• View the GitHub repository

Contributing

Found a bug? Want to add a helper? Read Contributing.

License

LGPL-3.0-or-later — see License for a summary and LICENSE for the full text.