Herb Syntax Tree Printer

Package: @herb-tools/printer

---

AST printer infrastructure for lossless HTML+ERB reconstruction and AST-to-source code conversion for the Herb Parser Syntax Tree.

Installation

:::code-group
``shell [npm]
npm add @herb-tools/printer
`

`shell [pnpm]
pnpm add @herb-tools/printer
`

`shell [yarn]
yarn add @herb-tools/printer
`

`shell [bun]
bun add @herb-tools/printer
`
:::

$3

#### IdentityPrinter (Provides lossless reconstruction of the original source)

For lossless reconstruction of the original source:

`javascript
import { IdentityPrinter } from '@herb-tools/printer'
import { Herb } from '@herb-tools/node-wasm'

await Herb.load()

const parseResult = Herb.parse(
'

Create custom printers by extending the base Printer class and override specific visitors for custom behavior:

`typescript
import { Printer } from "@herb-tools/printer"
import { HTMLAttributeNode } from "@herb-tools/core"

class CustomPrinter extends Printer {
protected write(content: string) {
super.write(content.toUpperCase())
}

protected visitHTMLAttributeNode(node: HTMLAttributeNode) {
// do nothing to strip attributes
}
}
`

and then printing the result using print

`js
import { Herb } from "@herb-tools/node-wasm"

await Herb.load()

const parseResult = Herb.parse(
'

`typescript
import { IdentityPrinter, DEFAULT_PRINT_OPTIONS } from "@herb-tools/printer"
import type { PrintOptions } from "@herb-tools/printer"

const printer = new IdentityPrinter()

// Will throw error if node has parse errors (default behavior)
const output1 = printer.print(nodeWithErrors)

// Will print the node despite parse errors
const output2 = printer.print(nodeWithErrors, { ignoreErrors: true })
`

When ignoreErrors is false (default), the printer will throw an error if you attempt to print a node that contains parse errors. Set ignoreErrors to true to print nodes with errors, which can be useful for debugging or partial AST reconstruction.

:::warning Important
The Printer expects the source to be parsed using the track_whitespace: true parser option for accurate source reconstruction.
:::

#### CLI Usage

`bash


Basic round-trip printing