Formatting Move Contracts

movefmt is a formatter tool that makes Move code much easier to write, read, and maintain — greatly improving the development experience on Aptos.

movefmt is integrated into the Aptos CLI. To begin using it, first install it using the CLI update command.

# Install movefmt for first time usage
aptos update movefmt

To install a specific version of movefmt:

# Install movefmt with the target <VERSION>
aptos update movefmt --target-version <VERSION>

The latest release of movefmt can be found here.

Similar to compilation and testing, you can use the following command to format the Move package:

# Format the Move package
aptos move fmt

Different ways of emitting the formatting result is supported:

# Format and overwrite all the target move files in the package.
# This is the default behavior if `--emit-mode` is not explicitly specified
aptos move fmt --emit-mode=overwrite

# Print the formatting result to terminal
aptos move fmt --emit-mode=std-out

# Print the formatting result to new files with the suffix `.fmt.out` in the same directory
aptos move fmt --emit-mode=new-file

# Print the difference between before and after formatting
aptos move fmt --emit-mode=diff

movefmt also provides different options to configure how the code will be formatted. Here is the default configuration:

max_width = 90 # each line can have at most 90 characters
indent_size = 4 # the indent is 4 spaces
tab_spaces = 4 # each tab is identical to 4 spaces
hard_tabs = false # when a tab is inserted, it will be automatically replaced by 4 spaces

To override the default option, users can either specify a configuration file movefmt.toml and put it in Move package directory or manually specify it in the command line:

# When formatting the code, set `max_width` to 80 and `indent_size` to 2
aptos move fmt --config max_width=80,indent_size=2

Aptos Labs remains committed to improving the developer experience for builders using Move on Aptos. If you’re interested in shaping the style guidelines for Move, we would love to hear your comments and feedback here.