ferristseng/rust-sformat-dynamic

Dynamic string formatting for Rust

sformat-dynamic

Dynamic string formatting for Rust.

This crate tries to mimic the std::fmt syntax as closely as possible. One notable differentiation thus far is that the dynamic string format only supports named parameters like {name}, and not positional parameters like {}.

Always use the compile-time format! macro if you can. There are some situations where you might need a dynamic string formatting engine, for example if you need a lightweight library way for users to specify their own formats in a config file or something similar. Again, using dynamic string formatting is far less secure than using the compile-time format! macro, so always prefer that!

This is still a WIP, so use at your own risk!

Examples

See ./sformat-dynamic/examples for more examples.

// Note: This example requires the "derive" feature.
use sformat_dynamic::{compile, derive::Context};

#[derive(Context)]
struct ContextImpl {
  value: usize
}

let context = ContextImpl { value: 99 };
let format = compile("Value is {value:+010}").unwrap();
let formatted = format.format_str(&context).unwrap();

assert_eq!(formatted, "Value is +000000099");

You can also use a HashMap when specifying the context, although it is significantly more verbose.

use sformat_dynamic::{compile, TypedValue};
use std::collections::HashMap;

let context = HashMap::from([
    ("name", TypedValue::Str("Ferris"))
]);
let format = compile("Hello {name: >16}!").unwrap();
let formatted = format.format_str(&context).unwrap();

assert_eq!(formatted, "Hello           Ferris!")

Feature Parity

Consult the str::fmt documentation for what these features actually mean.

Feature	Implemented	Future Plan to Implement
Named Argument {name}	✅	N/A
Positional Argument {}	❌	❌
Fill / Alignment < , ^ , >	✅	N/A
Sign Flag +	✅	N/A
Alternate Form Flag #	❌	🤔
Zero Flag 0	✅	N/A
Precision - Fixed .N	✅	N/A
Precision - Arg .N$	❌	❌
Precision - Astrix .*	❌	❌

Derive Types

A table of types that can be derived using sformat-dynamic-derive.

Type	Implemented	Future Plan to Implement
&T : Debug	❌	✅
&T : Display	❌	✅
&str	✅	✅
isize	✅	N/A
i64	✅	N/A
i32	✅	N/A
i16	✅	N/A
i8	✅	N/A
usize	✅	N/A
u64	✅	N/A
u32	✅	N/A
u16	✅	N/A
u8	✅	N/A
f64	✅	N/A
f32	✅	N/A
bool	✅	N/A

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.