indentkit

Detect and convert indentation. Figure out whether a string is indented with tabs or N spaces — like Node's detect-indent (a Prettier dependency) — and re-indent between styles. Zero dependencies, #![no_std].

use indentkit::{detect, reindent, indent, IndentStyle};

let code = "fn main() {\n  println!(\"hi\");\n}\n";

// Detect
assert_eq!(detect(code), IndentStyle::Spaces(2));

// Convert 2-space -> tabs
assert_eq!(reindent(code, IndentStyle::Tabs), "fn main() {\n\tprintln!(\"hi\");\n}\n");

// Build indentation for code generation
assert_eq!(indent(2, IndentStyle::Spaces(4)), "        ");

Why indentkit?

The Rust ecosystem's only detect-indent port is a stale v0.1.0 from 2023 and detects only. indentkit is a small, well-tested toolkit that also converts between styles — useful for formatters, linters, code generators, and editor tooling — and runs in no_std environments with no dependencies.

	detects	converts	no_std	deps
`indentkit`	✅	✅	✅	0

Install

[dependencies]
indentkit = "0.1"

API

Function	Purpose
`detect(text) -> IndentStyle`	Detect tabs vs N spaces (or `Unknown`)
`reindent(text, to) -> String`	Re-indent to a target style (auto-detects source)
`indent(level, style) -> String`	Build indentation for a nesting level (codegen)
`IndentStyle::unit() -> String`	The one-level indent string (`"\t"`, `" "`, …)

IndentStyle is Tabs, Spaces(usize), or Unknown, and implements Display ("tab", "4 spaces", "unknown").

Behavior notes

Detection counts each indentation step (the change in width between lines) by type and picks the most frequent — robust against alignment, continuation, and block-comment * lines. Ties resolve to the step seen first.
Blank and whitespace-only lines are ignored when detecting, and emitted as clean empty lines when re-indenting (no trailing whitespace).
reindent rewrites leading indentation by nesting level; sub-level alignment after the indent is preserved as-is. Lines mixing leading tabs and spaces are converted on a best-effort basis.
If the source has no detectable indentation, or the target is Unknown (or Spaces(0)), reindent returns the text unchanged.

no_std

indentkit is #![no_std] and only needs alloc. It builds for bare-metal targets such as thumbv7em-none-eabi.

License

Licensed under either of Apache-2.0 or MIT at your option.