print-break

A simple Rust debugging macro that pretty-prints variables and pauses execution. No debugger needed.

Features

• Pretty-prints any Debug type with syntax highlighting
• Auto-detects JSON, TOML, YAML strings and formats them nicely
• Pauses execution until you press Enter
• Compiles to nothing in release builds - zero overhead in production
• Disable at runtime with PRINT_BREAK=0
• Interactive controls: continue, quit, skip remaining, show more
• Conditional breakpoints with print_break_if!
• Non-TTY safe - won't hang in CI/piped output
• Breakpoint counter - know which breakpoint you're at

Installation

[dependencies]
print-break = "0.1"

Usage

use print_break::{print_break, print_break_if};

fn main() {
    let user_id = 42;
    let name = "ferris";
    let items = vec![1, 2, 3];

    // Basic breakpoint
    print_break!(user_id, name, items);

    // Conditional breakpoint (great for loops)
    for i in 0..100 {
        print_break_if!(i == 50, i);
    }

    // JSON strings are auto-formatted
    let json = r#"{"status": "ok", "data": [1, 2, 3]}"#;
    print_break!(json);
}

Output

┌─ BREAK #1 ─────────────────────────────────────
│ src/main.rs:8                                  │
├────────────────────────────────────────────────
│ user_id = 42
│ name = "ferris"
│ items = [1, 2, 3]
└────────────────────────────────────────────────
[Enter=continue, m=more, s=skip all, q=quit]

Interactive Controls

When paused at a breakpoint:

Environment Variables

# Disable all breakpoints
PRINT_BREAK=0 cargo run

# Re-enable (default)
PRINT_BREAK=1 cargo run

CI / Non-Interactive Mode

When stderr is not a TTY (piped to file, running in CI), print-break automatically:

• Disables colors
• Skips the pause (won't hang your CI)
• Still prints the debug output for logging

Conditional Breakpoints

Perfect for debugging loops:

use print_break::print_break_if;

for i in 0..1000 {
    // Only break when i is 500
    print_break_if!(i == 500, i);

    // Break when condition is met
    print_break_if!(some_value > threshold, some_value, threshold);
}

Release Builds

In release builds (cargo build --release), all print_break! and print_break_if! calls compile to nothing - zero runtime overhead.

Format Detection

Strings are automatically detected and pretty-printed:

• JSON - Objects and arrays
• TOML - Configuration files
• YAML - Configuration files
• Plain text - Word-wrapped at 80 characters

Long output is truncated at 50 lines. Press m to see the full output.

License

MIT