cli-forge 0.4.0

What's here

As of v0.4.0, the output layer, the command layer, and the help engine are implemented and stable:

• Plain output — out / err: one call, no parsing, no allocation for a string literal. The hot path stays cheap.
• Three styling paths — a chainable style builder, inline parse tags, and a named define_tag / tag registry. All three render to identical bytes for the same intent.
• Full color — the eight standard names plus any 24-bit color via hex or RGB, with graceful downgrade to 256- or 16-color terminals and clean fall-back to plain text on pipes, NO_COLOR, or the Windows console without ANSI.
• Command tree — a recursive Command tree with arg/flag parsing and aliases, registered into an App from anywhere (not just main), with .hidden() and .requires_auth() flags and structured, non-panicking errors.
• Help & version — auto-generated --help / -h (top-level and per-command) and --version / -V, rendered through the output layer with injectable header/footer.

The auth seam (v0.5.0) lands next — see the ROADMAP.

Installation

[dependencies]
cli-forge = "0.4"

Color is on by default. For a build that never emits escape sequences (the API stays complete; every styled value renders as its plain text):

[dependencies]
cli-forge = { version = "0.4", default-features = false, features = ["std"] }

Quick Start

use cli_forge::{define_tag, err, out, parse, style, tag};

// Plain output — the common case.
out("building...");
err("something went wrong");

// Styling, three ways, all rendering to the same bytes for the same intent:
out(style("done").green().bold());                          // builder
parse("<c=red><b>ERROR:</b></c> <c=#ff8800>low disk</c>");  // inline tags
define_tag("error", style("").red().bold());                // named registry
out(tag("error").render_with("build failed"));

The three styling paths

The same styled line, produced three ways. The choice is ergonomic, not visual — the bytes are identical.

use cli_forge::{define_tag, out, parse, style, tag};

// 1. Builder — chain methods; the result is `Display`. Best for computed/one-off.
out(style("ERROR: build failed").red().bold());

// 2. Tags — one string with inline markup. Best when text and style live together.
parse("<c=red><b>ERROR: build failed</b></c>");

// 3. Named registry — define the look once, reuse by name across the program.
define_tag("error", style("").red().bold());
out(tag("error").render_with("ERROR: build failed"));

Tag grammar: <b>…</b> (bold), <u>…</u> (underline), <c=VALUE>…</c> (color, where VALUE is a named color, #rrggbb, or r,g,b), and </> to close the innermost tag. Tags nest; unrecognized tags print literally, so parse never rejects input.

Colors and terminals

Colors are the eight standard names, plus any 24-bit value:

use cli_forge::{out, style};

out(style("amber").hex("#ff8800"));
out(style("teal").rgb(0, 200, 120));
out(style("link").hex("#3b82f6").underline());

The terminal's capability is detected once. A 24-bit color renders exactly on a true-color terminal, downgrades to the nearest 256- or 16-color value where that is all the terminal supports, and falls away to plain text when output is a pipe, NO_COLOR is set, or the crate is built without color. CLICOLOR_FORCE overrides detection and forces color on. The Windows console is handled behind the same API — virtual-terminal mode is enabled automatically, with a plain-text fall-back if it cannot be.

Commands

Build a recursive command tree, register commands into an App from anywhere, and let parse resolve the invocation, parse arguments, and run the selected command's handler:

use cli_forge::{App, Arg, Command, out};

let mut app = App::new("forge");

app.register(
    Command::new("build")
        .about("compile the project")
        .arg(Arg::flag("release").short('r'))
        .arg(Arg::option("jobs").short('j').default("1"))
        .run(|m| out(format!(
            "release={} jobs={}",
            m.flag("release"),
            m.value("jobs").unwrap_or("?"),
        ))),
);

app.register(
    Command::new("remote").subcommand(
        Command::new("add")
            .arg(Arg::positional("url").required(true))
            .run(|m| out(format!("added {}", m.value("url").unwrap_or("?")))),
    ),
);

let _ = app.parse();

Commands register from anywhere — a command built in a non-main module is reachable and behaves identically, the limitation that made the predecessor unusable. Give a command extra names with .alias("rm") / .aliases(["rm", "del"]); aliases resolve to the canonical command. The parser handles the standard forms (--long, --long=value, -s, -svalue, bundled -abc, positionals, --), and malformed input becomes a structured ParseError: parse prints it and exits 2, never panicking; try_parse_from returns it instead. .hidden() keeps a command invokable but out of help; .requires_auth() records the flag for the auth seam (v0.5.0).

Help and version come for free. -h / --help renders styled help for the app or any command (with your help_header / help_footer); -V / --version prints App::version(...). App::help() renders the top-level help as a string whenever you want it. Both exit 0 under parse; try_parse_from returns them as ParseError::HelpRequested / VersionRequested control signals.

Feature flags

Examples

Runnable examples live in examples/:

cargo run --example quick_start     # plain output and one styled line
cargo run --example three_paths     # the same line, three ways
cargo run --example colors          # named, hex, and rgb color
cargo run --example status_report   # a realistic deploy-style status report
cargo run --example commands -- build --release -j 8   # the command tree

Force color when output is captured, or disable it, to see both paths:

CLICOLOR_FORCE=1 cargo run --example status_report
NO_COLOR=1       cargo run --example status_report

Performance

The plain path is allocation-free for a string literal — proven by a counting-allocator test (tests/allocation.rs), not asserted. Local Criterion means (Windows x86_64, release build):

Styling costs more than the plain path because it builds an owned String and encodes escape sequences — a cost paid only when you opt into color. Reproduce with cargo bench --bench bench.

Status

v0.4.0 ships the help engine (plus aliases and version) on top of the command and output layers, per the ROADMAP and docs/API.md. The auth seam (v0.5.0) follows; the public API freezes at 1.0.0.

Contributing

See dev/DIRECTIVES.md for engineering standards and the definition of done. Before a PR: cargo fmt --all, cargo clippy --all-targets --all-features -- -D warnings, and cargo test --all-features must be clean.