Plugins are ways of adding new languages to Prettier. Prettier's own implementations of all languages are expressed using the plugin API. The core `prettier` package contains JavaScript and other web-focussed languages built in. For additional languages you'll need to install a plugin.
Plugins are automatically loaded if you have them installed in your `package.json`. Prettier plugin package names must start with `@prettier/plugin-` or `prettier-plugin-` to be registered.
Languages is an array of language definitions that your plugin will contribute to Prettier. It can include all of the fields specified in [`prettier.getSupportInfo()`](./api.md#prettiergetsupportinfo-version).
It **must** include `name` and `parsers`.
```js
export const languages = [
{
// The language name
name: "InterpretedDanceScript",
// Parsers that can parse this language.
// This can be built-in parsers, or parsers you have contributed via this plugin.
parsers: ["dance-parse"]
}
];
```
### `parsers`
Parsers convert code as a string into an [AST](https://en.wikipedia.org/wiki/Abstract_syntax_tree).
The key must match the name in the `parsers` array from `languages`. The value contains a parse function, an AST format name, and two location extraction functions (`locStart` and `locEnd`).
Printers convert ASTs into a Prettier intermediate representation, also known as a Doc.
The key must match the `astFormat` that the parser produces. The value contains an object with a `print` function and (optionally) an `embed` function.
```js
export const printers = {
"dance-ast": {
print,
embed
}
};
```
Printing is a recursive process of coverting an AST node (represented by a path to that node) into a doc. The doc is constructed using the [builder commands](https://github.com/prettier/prettier/blob/master/commands.md):
```js
const { concat, join, line, ifBreak, group } = require("prettier").doc.builders;
```
The signature of the `print` function is:
```ts
function print(
// Path to the AST node to print
path: FastPath,
options: object,
// Recursively print a child node
print: (path: FastPath) => Doc
): Doc;
```
Check out [prettier-python's printer](https://github.com/prettier/prettier-python/blob/034ba8a9551f3fa22cead41b323be0b28d06d13b/src/printer.js#L174) as an example.
Embedding refers to printing one language inside another. Examples of this are CSS-in-JS and Markdown code blocks. Plugins can switch to alternate languages using the `embed` function. Its signature is:
```ts
function embed(
// Path to the current AST node
path: FastPath,
// Print a node with the current printer
print: (path: FastPath) => Doc,
// Parse and print some text using a different parser.
// You should set `options.parser` to specify which parser to use.
A `util` module from prettier core is considered a private API and is not meant to be consumed by plugins. Instead, the `util-shared` module provides the following limited set of utility functions for plugins:
