A code formatter for Haxe

cli, formatter, style, haxe
haxelib install formatter 1.10.0


Haxe Formatter

Haxelib Version Build Status Haxe-Formatter Linux codecov Gitter chat

A Haxe Code Formatter based on the tokentree library.

VSCode format on save

It's recommended to make a backup of your files and use a diff tool.


  • Formatting handles:
    • Indentation
    • Whitespace
    • Wrapping
    • Empty Lines
    • Same Line
    • Line Ends
  • hxformat.json configuration files
  • supports latest Haxe 4 syntax
  • supports conditional compilation
  • Visual Studio Code Integration


Apart from IDE integration, there's also a command line version of haxe-formatter that can be installed from haxelib:

haxelib install formatter

Bulk Formatting

  • Run haxelib run formatter -s src to format folder src.
  • Run haxelib run formatter -s src -s test to format folders src and test.

If the node command is available on your system, the formatter automatically uses its NodeJS version instead of a Neko build (which is considerably faster).

Single File Formatting

Run haxelib run formatter -s src/Main.hx to format file src/Main.hx.

Format check

Use --check to run formatter in check mode to see if code is properly formatted without modifying it. This can be especially useful in a CI environment.

Piped mode

You can run formatter in "piped mode", where it reads code from STDIN and prints formatted results to STDOUT. You can enable piped mode by giving --stdin on command line. In piped mode formatter requires exactly one --source <path> to make sure configuration file detection knows where to start.

Formatter does not support a stream mode, where you can provide an endless stream of code to be formatted, your input data needs some sort of end of file.

Formatter will print formatted code to STDOUT.

In case of errors, it will print your input file without modifications (as long as formatter is able to read your input). When an error occurs formatter sets an exit code and prints an error message to STDERR.

Exit code Description STDOUT
0 Formatting succeeded Formatted code
-1 no input data or other unknwon error there might not be output
1 Formatting is disabled for --source <path> unformatted input
2 Formatter error unformatted input
3 no reference or invalid path specified via --source <path> unformatted input

Sample call: haxelib run formatter --stdin -s src/Main.hx < /tmp/code.txt > src/FormattedCode.hx


Formatter uses hxformat.json files for configuration. It searches for a hxformat.json file closest to the file being formatted, starting with the file's folder and moving upward all the way to your root folder. A configuration file in a subfolder will always overwrite any settings from a top or higher level folder.

The VSCode extension comes with a JSON schema providing completion and limited documentation for edition hxformat.json files:

JSON schema for hxformat.json in VSCode

An empty hxformat.json (containing only {}) or having hxformat.json will result in formatting using the built-in default which is the coding style of formatter itself.

When creating your custom hxformat.json file, you only need to provide settings that you want to override with respect to the built-in default. So configuration always starts with the default style of formatter. The following example changes curly braces placement and indentation to 4 space characters:

    "lineEnds": {
        "blockCurly": {
            "leftCurly": "both",
            "emptyCurly": "noBreak"
    "indentation": {
        "character": "    "

Pro tip: Visual Studio Code has Format on Save and Format on Paste settings that you can enable by adding

"[haxe]": {
  "editor.formatOnSave": true,
  "editor.formatOnPaste": true

to your configuration (local or global). formatOnPaste will also give you Format Selection in .hx files.

Ways to opt-out of formatting

  • turn off formatter in your IDE / don't run CLI version
    • affects all files
  • place a hxformat.json file with { "disableFormatting": true } in you workspace
    • affects all files and subfolders from where you placed hxformat.json
    • since formatter searches for a hxformat.json file closest to the file being formatted, you can disableFormatting in a subfolder, while enabling it everywhere else
    • you can reverse a disableFormatting by placing a hxformat.json with {} (for built-in formatter config) in a subfolder, every file in that subfolder and below will get formatted
  • use excludes inside your hxformat.json to specify a number of regexes, that will exclude any filename from formatting matching any one of these regexes
  • use // @formatter:off and // @formatter:on comments inside your code to turn off formatting for parts of your code, it's line based and includes lines containing // @formatter:off and // @formatter:on.

How to start using formatter in your projects

Switching from manually formatted source code to an automated formatter workflow can be a lot of work. The following steps should help you get started:

  1. make sure you have an unmodified checkout / clone of your project (assuming you are using a VCS)
  2. run formatter on your source folder(s) - if you already have a hxformat.json formatter will use it, otherwise it will use built-in defaults.
  3. use your IDE's diff view, or some other diff viewer to look at the changes formatter made - chances are you don't like what you see, at least for some parts
  4. open hxformat.json and add / change configuration settings for formatting choices you did not like - we recommend using VSCode, since it has a JSON schema for hxformat.json files providing completion support (including (incomplete) documentation for configuration options)
  5. goto step 1 and rerun formatter until you are happy with the resulting changelist or run out of options to try - you can rerun formatter on already formatted code, but some options might work better on unmodified sources (e.g. using keep in wrapping rules will try to conserve your original line breaks, but it will not recreate them after a previous formatter run removed them)

Depending on the size of your project your initial changelist is going to be large and quite possibly contains every source file. When you have a hxformat.json file that works for you, you can enable formatting in VSCode or add an external programm / command that simply calls haxelib run formatter -s <filename> (or node <path_to_formatter>/run.js -s <filename>) when saving or pressing a hotkey.


  • improve wrapping

Compiling formatter

git clone https://github.com/HaxeCheckstyle/haxe-formatter.git
npm install
lix download
haxe buildAll.hxml # for Neko, NodeJS and Java version + run Unittests and create schema
haxe buildCpp.hxml # for C++ version

Compiling with Haxe 3

git clone https://github.com/HaxeCheckstyle/haxe-formatter.git
mv haxe_libraries haxe4_libraries
mv haxe3_libraries haxe_libraries
npm install
lix use haxe 3.4.7
lix download
haxe buildAll.hxml # for Neko, NodeJS and Java version + run Unittests and create schema
haxe buildCpp.hxml # for C++ version


To run all unittests simply use npx haxe test.hxml

if you want to only run a single testcase you can either:

  • use vshaxe-debug-tools extension in VSCode which provides a Run current formatter test command that runs on any .hxtest file
  • run it on command line by
    1. place a file called single-run.txt in your workspace's test folder
    2. make single-run.txt contain your testcase's path and name (without .hxtest extension) like test/testcases/sameline/issue_235_keep_if_else
    3. run npx haxe test.hxml
    4. you will get a test/formatter-result.txt containing two sections with result and gold (empty sections for green tests)

Removing test/single-run.txt makes haxe test.hxml do a full run. vshaxe-debug-tools is recommended since it performs all manual steps outlined and also opens a diff-view editor so you can easily compare result and gold.