rebar3_format

A rebar plugin for code formatting

Build

$ rebar3 compile

Use

Add the plugin to your rebar config:

{profiles, [rebar3_format]}

Then just call your plugin directly in an existing application:

$ rebar3 format

This will format every Erlang file under /src by default. You can specify the directory/file to format as following:

$ rebar3 format --files src/my_subdir/*.erl
$ rebar3 format --files src/other_subdir/my_file.erl
$ rebar3 format --files test/**/*.erl

To save the formatted files in a different directory you have to pass it as a parameter:

$ rebar3 format --output formatted/

Configuration

The plugin supports the following configuration options in the format section of rebar.config:

• files ([file:filename_all()]):
  • List of wildcard patterns representing the files that will be formatted by default (i.e. when not using --files on command line).
  • The default value is ["src/**/*.?rl"]
• encoding(none | epp:source_encoding()):
  • Encoding to use when writing files.
  • The default value is none.
• paper(pos_integer()):
  • Specifies the preferred maximum number of characters on any line, including indentation.
  • The default value is 100.
• ribbon(pos_integer()):
  • Specifies the preferred maximum number of characters on any line, not counting indentation.
  • The default value is 80.

Per-File Configuration

You can tweak any of the options above for a particular file, using the format attribute in it, like this:

-format([{paper, 80}]).

Test

To test the plugin just run make test.
It will copy test_app files into test_app/after and run rebar3 format inside it.
Add modules with any "tricky" formatting you want to test_app/src, and push them to github including the after results.

The after results can be tought as the expected output behaviour.
It should be no changes afterwards when running make test, unless the format rules got updated.

You can run make diff to check diff between test_app/src and test_app/after/src.

Contribute

To contribute to rebar3_format, please refer to CONTRIBUTING.