rustfmt-repl

A tiny adapter that lets rustfmt format Rust statement snippets used in Markdown code blocks and REPLs.

It first runs rustfmt on the input as a complete Rust source file. If that fails, it temporarily wraps the input in fn main(), formats it, and removes the wrapper again.

Build

cargo install rustfmt-repl

Usage

Read from stdin and write to stdout:

'let x=(1,2); dbg!(x,    x.0);' | rustfmt-repl

Or format a file in place:

rustfmt-repl path\to\snippet.rs

For repeated formatting of many snippets, enable the opt-in content cache:

rustfmt-repl --cache path\to\snippet.rs

Markdown code-block formatters

rustfmt-repl can be used as the Rust formatter behind either mdsf or Panache. The orchestrator extracts Rust code blocks; rustfmt-repl makes complete files and statement snippets usable with rustfmt.

Use one of these integrations in a formatting chain, not both.

mdsf

Add the following language entry to mdsf.json:

{
  "languages": {
    "rust": {
      "binary": "rustfmt-repl",
      "arguments": ["--cache", "$PATH"],
      "stdin": false
    }
  }
}

mdsf gives rustfmt-repl a temporary file through $PATH, so this example uses file mode.

Panache

Add the following entries to panache.toml:

external-max-parallel = 8

[formatters]
rust = "rustfmt-repl"
rs = "rustfmt-repl"

[formatters.rustfmt-repl]
cmd = "rustfmt-repl"
args = ["--cache"]
stdin = true

Panache sends each code block through stdin and can run independent code-block formatters in parallel. rustfmt-repl still performs the snippet wrapping and unwrapping required by rustfmt.

PATH

Make sure Cargo's binary directory is available on PATH. Its usual location is $HOME/.cargo/bin on Unix-like systems and %USERPROFILE%\.cargo\bin on Windows. If the editor does not inherit your shell environment, use the full path to the executable in your local configuration.