rustfmtifchain

A wrapper around [rustfmt] to format inside [if_chain] invocations

rustfmt_if_chain is not guaranteed to work on all Rust source files, but it should work on most of [Clippy]'s source files.

cargo install rustfmt_if_chain

``` Usage: rustfmtifchain [ARGS]

Arguments ending with .rs are considered source files and are formatted. All other arguments are forwarded to rustfmt, with one exception.

The one argument not forwarded to rustfmt is --preformat-failure-is-warning. If this option is passed and rustfmt fails on an unmodified source file, a warning results instead of an error. ```

Example

• Before

  rust fn main() -> PhilosophicalResult<()> { if_chain! { if let Some (it) = tree . falls_in (forest) ; if ! listeners . any (| one | one . around_to_hear (it)) ; if ! it . makes_a_sound () ; then { return Err (PhilosophicalError :: new ()) ; } } Ok(()) }

• After

  rust fn main() -> PhilosophicalResult<()> { if_chain! { if let Some(it) = tree.falls_in(forest); if !listeners.any(|one| one.around_to_hear(it)); if !it.makes_a_sound(); then { return Err(PhilosophicalError::new()); } } Ok(()) }

How it works

1. Preformat check: rustfmt is run on the original source file to verify that it can be formatted.*
2. The if_chain invocations in the original source file are rewritten according to the following rules, where x is an identifier that does not appear elsewhere in the file:
   • if_chain! -> fn x()
   • if ... ; -> if ... { x; }
   • then -> if x
3. rustfmt is run on the file resulting from step 1.
4. In the file resulting from step 2, the rewrites of step 1 are undone.

* Step 0 is not strictly necessary, but it helps to identify failures of step 2 caused by the limitations of step 1.

Known problems

rustfmt_if_chain --check FILENAME does not work correctly. A workaround is to use rustfmt_if_chain FILENAME && git diff --exit-code.