Prettier for NGINX

---

A Prettier plugin that formats NGINX configuration files, including OpenResty *_by_lua_block directives. It is written in TypeScript, depends only on Prettier, and needs Prettier 3.6 or later.

Getting Started

Install Prettier and the plugin:

npm install --save-dev prettier prettier-plugin-nginx

Register the plugin in your Prettier configuration:

{
  "plugins": ["prettier-plugin-nginx"]
}

The plugin formats these files automatically:

• files with the extensions .nginx, .nginxconf and .vhost,
• nginx.conf, mime.types, fastcgi_params, fastcgi.conf, scgi_params, uwsgi_params, proxy_params, koi-utf, koi-win and win-utf,
• inside a directory named nginx: any .conf or .template file, such as docker/nginx/default.conf, and any file in a sites-available, sites-enabled, conf.d or snippets directory, such as /etc/nginx/sites-available/default, apart from dotfiles, certificates, scripts, logs and backups. List anything else that lives there, such as a supervisord.conf, in .prettierignore.

To format other files, assign them the nginx parser with an override:

{
  "plugins": ["prettier-plugin-nginx"],
  "overrides": [
    {
      "files": ["*.conf", "sites-enabled/*"],
      "options": { "parser": "nginx" }
    }
  ]
}

Or from the command line:

npx prettier --write --plugin prettier-plugin-nginx --parser nginx default.conf

Example

A messy file like this...

server {
# server definition
listen 443 ssl; listen [::]:443 ssl;
server_name example.com;
location / { proxy_pass http://proxy; proxy_set_header Host $http_host;
proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_read_timeout 1000; }
# end server definition
}

...is transformed to this:

server {
    # server definition
    listen      443 ssl;
    listen      [::]:443 ssl;
    server_name example.com;

    location / {
        proxy_pass         http://proxy;
        proxy_set_header   Host $http_host;
        proxy_set_header   X-Real-IP $remote_addr;
        proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header   X-Forwarded-Proto $scheme;
        proxy_read_timeout 1000;
    }
    # end server definition
}

Formatting

This plugin, like Prettier, is opinionated. The style follows the configuration examples in the NGINX documentation:

• Blocks are indented by one tabWidth, four spaces by default. Block directives are separated from their neighbours by a blank line, and a single blank line between other statements is kept; blank lines at the start or end of a block are not.
• The parameters of the simple directives in a block, or at the top level, are aligned to one column. A name that ends beyond the middle of the line stays out of the alignment, so one long name does not push everything else to the right.
• Parameters that do not fit within printWidth wrap onto continuation lines; the first parameter stays on the directive's line.
• Comments stay where they are: on their own line, after a ;, or after a { or } on the same line. A comment between a directive's parameters ends the line it is on, and one right before the ; or { moves after it, joining any comment already there.
• Every word is printed exactly as written. Quotes, escapes, regular expressions and multi-line strings are never altered, and an if condition is only re-spaced as if (...), on one line. With endOfLine set to crlf, the line breaks inside multi-line strings change with the rest of the file, and a word continued across lines with a backslash would be split, so keep the default lf for such files. cr is refused, since NGINX ends comments only at a line feed.
• *_by_lua_block bodies are re-indented as a unit; the Lua inside them is not otherwise changed, and lines inside [[...]] long brackets are kept byte for byte. If a Prettier plugin providing a lua parser is loaded, the Lua is formatted with it instead.
• A # prettier-ignore comment on its own line keeps the next statement, including a block and its original inner indentation, exactly as written. Other comments and blank lines may sit between the two.
• Range formatting (--range-start, --range-end) is not supported; with a range the file is left unchanged.
• # @format or # @prettier on the first line works with --require-pragma and --insert-pragma, and # @noformat or # @noprettier with --check-ignore-pragma.

Invalid configuration, such as a directive without its ;, is reported as a syntax error with its location; NGINX would reject it too. Template syntax is not supported: {{ ... }} is rejected as a stray brace, and <% ... %> is not detected at all, so it would be merged into the surrounding directive. envsubst style ${VAR} references are fine.

Configuration

The following options are available.

Note that tabWidth defaults to 4 rather than Prettier's 2, to match the NGINX documentation.

Contributing

Bug reports and pull requests are welcome on GitHub.

Development needs Node.js 24 (see .node-version). npm test builds the plugin and runs the test suite; CI also runs npm run typecheck and npm run format:check, and npm run coverage reports coverage. The fixtures under test/fixtures are grouped by case; each case holds two example configurations taken from the NGINX or OpenResty documentation or from NGINX's conf/ directory, cited on their first line and cut down to an excerpt where marked, and one written to break the formatter, next to their formatted output or expected error. A documented example is named after its source page or file and its position among that page's configuration examples. Run npm run test:update after an intentional change to the output.

License

The package is available as open source under the terms of the MIT License.