Cheatrustfmt Rust code formatter
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Start here
rustup component add rustfmt
Install it
cargo fmtFormat the whole crate
cargo fmt --check
Verify only (CI)
cargo fmt --allWhole workspace
rustfmt <file.rs>
Format one file
rustfmt --edition 2021 <file.rs>
Set parse edition
rustfmt --print-config default rustfmt.toml
Write a config
cargo +nightly fmt
Use nightly options
Concepts
- Source files *.rs
- rustfmt rustfmt.toml + style_edition
- Result files, stdout or diff
Install and run
rustup component add rustfmt
Install on the stable toolchain
rustup component add rustfmt --toolchain nightly
Install on nightly
cargo fmtFormat all targets of the crate
cargo fmt --allFormat every workspace member
cargo fmt -p <crate>
Format one package
cargo fmt -- <rustfmt-args>
Pass flags through to rustfmt
cargo +nightly fmt
Run the nightly formatter
rustfmt <file.rs>
Format a file and its out-of-line modules
rustfmt <a.rs> <b.rs>
Format several files in place
echo 'fn main(){}' | rustfmt
Format stdin to stdout
rustfmt --version
Show the rustfmt version
rustfmt --helpList all flags
rustfmt --help=config
List config options and defaults
RUSTFMT=<path> cargo fmt
Make cargo use a specific binary
Checking and output
cargo fmt --check
Exit 1 and print a diff if unformatted
cargo fmt --all -- --check
Check the whole workspace in CI
rustfmt --check <file.rs>
Check one file without writing
rustfmt --emit stdout <file.rs>
Print the result instead of writing
rustfmt --emit files <file.rs>
Overwrite files (the default)
rustfmt -l <file.rs>
List files that would change
rustfmt --color never --check <file.rs>
Disable colored diff output
Configuration
rustfmt.toml / .rustfmt.toml
Config file in the project or any parent dir
rustfmt --print-config default rustfmt.toml
Write all defaults to a file
rustfmt --print-config current <file.rs>
Show the effective config for a file
rustfmt --print-config minimal rustfmt.toml
Write only non-default values
rustfmt --config-path <dir|file>
<file.rs>
Use a specific config
rustfmt --config max_width=80 <file.rs>
Override an option from the CLI
cargo fmt -- --config max_width=80,tab_spaces=2
Override options via cargo
edition = "2021"
Parse with this language edition
style_edition = "2024"
Pick the style guide edition
rustfmt --edition 2021 <file.rs>
Set the edition on the command line
rustfmt --style-edition 2024 <file.rs>
Set the style edition on the CLI
Common options (stable)
max_width = 100Maximum line width
tab_spaces = 4Spaces per indent level
hard_tabs = false
Indent with tabs instead of spaces
newline_style = "Auto"
Line endings: Auto, Native, Unix, Windows
use_small_heuristics = "Default"
Scale small-width limits: Off, Max, Default
fn_call_width = 60
Width before a call's args go vertical
chain_width = 60
Width before a method chain breaks
struct_lit_width = 18
Width before a struct literal breaks
match_block_trailing_comma
Comma after block match arms
match_arm_leading_pipes = "Never"
Leading | in match arms: Never, Always, Preserve
merge_derives = true
Merge adjacent #[derive] attributes
reorder_imports = true
Sort use statements within a group
reorder_modules = true
Sort mod declarations
hex_literal_case = "Preserve"
Hex digit case: Preserve, Upper, Lower
required_version = "1.8.0"
Fail if rustfmt version differs
Nightly-only options
unstable_features = true
Opt in to unstable options
imports_granularity = "Crate"
Merge imports: Preserve, Crate, Module, Item, One
group_imports = "StdExternalCrate"
Group imports: Preserve, StdExternalCrate, One
wrap_comments = true
Re-wrap long comments
comment_width = 80
Width used when wrapping comments
format_code_in_doc_comments
Format Rust code blocks in docs
format_strings = true
Break long string literals
normalize_comments = true
Turn /* */ into // where possible
imports_layout = "Vertical"
One import per line when braces
trailing_comma = "Vertical"
Trailing commas: Always, Never, Vertical
blank_lines_upper_bound = 1
Max consecutive blank lines
ignore = ["<path>"]
Skip files/dirs (gitignore patterns)
skip_children = true
Do not format out-of-line child modules
error_on_line_overflow = true
Report lines wider than max_width
Skipping and attributes
#[rustfmt::skip]
Do not format the next item or statement
#![rustfmt::skip]
Skip the whole module or file (inner attr)
skip_macro_invocations = ["<name>"]
Config form of macro skipping (nightly)
Recipes
cargo fmt --all -- --checkcargo clippy --all-targets -- -D warningsedition = "2021"style_edition = "2024"max_width = 100# nightly only:unstable_features = trueimports_granularity = "Crate"group_imports = "StdExternalCrate"rustup toolchain install nightly --component rustfmtcargo +nightly fmt --allrustfmt --check --edition 2021 src/main.rsecho $?
