Dompa

A lightweight, zero-dependency HTML5 document parser for Rust. Dompa takes an HTML string as input, parses it into a node tree, and provides an API for querying, manipulating, and serializing the node tree back to HTML.

Installation

Add Dompa to your Cargo.toml:

[dependencies]
dompa = "1.0.0"

Usage

Basic usage looks like this:

use dompa;

fn main() {
    let html = String::from("<div>Hello, World</div>");
    let nodes = dompa::nodes(html);
    
    /* gdb! output of nodes:
    [
        Block(
            BlockNode {
                name: "div",
                attributes: {},
                children: [
                    Text(
                        TextNode {
                            value: "Hello, World",
                        },
                    ),
                ],
            },
        ),
    ]
    */
        
    // Turn the node tree back into HTML
    let html_output = dompa::to_html(nodes);
}

Node Types

Dompa defines four types of nodes that represent HTML elements:

BlockNode

Represents standard HTML elements that can contain children:

A BlockNode can be created either by using the full, verbose way, such as:

use dompa::{Node, BlockNode};
use std::collections::HashMap;

let block_node = Node::Block(BlockNode {
  name: String::from("div"),
  attributes: HashMap::new(),
  children: Vec::new()
});

Or you can use a shorthand helper, like so:

let block_node = Node::block("div", HashMap::new(), vec![]);

But if you don't care about manually adding attributes then you can use an even shorter shorthand helper, like so:

let block_node = Node::simple_block("div", vec![]);

Example with content:

use dompa::Node;
use std::collections::HashMap;

// Create a div with text content
let div = Node::simple_block("div", vec![
    Node::text("Hello, World!")
]);

VoidNode

Represents self-closing HTML elements that cannot have children. Dompa automatically treats the following tags as void nodes:

• !doctype
• area
• base
• br
• col
• embed
• hr
• img
• input
• link
• meta
• source
• track
• wbr

A VoidNode can be created either by using the full, verbose way, such as:

use dompa::{Node, VoidNode};
use std::collections::HashMap;

let void_node = Node::Void(VoidNode {
    name: String::from("img"),
    attributes: HashMap::new()
});

Or you can use a shorthand helper, like so:

let void_node = Node::void("img", HashMap::new());

But if you don't care about manually adding attributes then you can use an even shorter shorthand helper, like so:

let void_node = Node::simple_void("img");

Example with attributes:

use dompa::{Node, NodeAttributeValue};
use std::collections::HashMap;

// Create an img element with attributes
let mut attrs = HashMap::new();
attrs.insert(String::from("src"), NodeAttributeValue::string("/images/logo.png"));
attrs.insert(String::from("alt"), NodeAttributeValue::string("Logo"));

let img = Node::void("img", attrs);

TextNode

Represents plain text content inside HTML elements:

A TextNode can be created either by using the full, verbose way, such as:

use dompa::{Node, TextNode};

let text_node = Node::Text(TextNode {
    value: String::from("Hello, World!")
});

Or you can use a shorthand helper, like so:

use dompa::Node;

let text_node = Node::text("Hello, World!");

FragmentNode

A special node type that allows grouping multiple nodes without creating a parent element:

A FragmentNode can be created either by using the full, verbose way, such as:

use dompa::{Node, FragmentNode};

let fragment_node = Node::Fragment(FragmentNode {
    children: vec![
        Node::text("First part "),
        Node::simple_void("br"),
        Node::text("Second part")
    ]
});

Or you can use a shorthand helper, like so:

use dompa::Node;

let fragment_node = Node::fragment(vec![
    Node::text("First part "),
    Node::simple_void("br"),
    Node::text("Second part")
]);

Essentially, a FragmentNode is a node which children replace itself.

HTML Parsing and Manipulation

nodes function

The nodes function parses an HTML string into a node tree:

let html = String::from("<h1>Title</h1><p>Content</p>");
let nodes = dompa::nodes(html);

traverse function

The traverse function allows you to manipulate the node tree by applying a callback function to each node:

let html = String::from("<h1>Old Title</h1><p>Content</p>");
let nodes = dompa::nodes(html);

// Update the title text
let updated_nodes = dompa::traverse(nodes, |node| {
    match node {
        Node::Block(block) if block.name == "h1" => {
            // Create new h1 with updated text
            let mut new_block = block.clone();
            new_block.children = vec![Node::text("New Title")];
            Some(Node::Block(new_block))
        },
        _ => Some(node.clone())
    }
});

The callback function must return an Option<Node>:

• If you return None for a node, it will be removed from the tree
• If you return Some(node), that node will be kept in the tree, whether it's the original or a replacement
• For nodes you don't want to modify, you must return the original node wrapped in Some() (typically Some(node.clone()))
• For nodes you want to modify, return a new or updated node wrapped in Some()

Note that the callback function is called for every node in the tree, so you need to handle all cases. In most cases, you'll have specific patterns you want to match and transform, and then a catch-all case that returns the original node.

to_html function

The to_html function serializes the node tree back to an HTML string:

let html = dompa::to_html(nodes);

Note that since the attributes are stored in a HashMap, their order is not guaranteed to be the same as in your HTML. However, to not have unpredictable results, Dompa sorts the attributes alphabetically in the output.

Working with Attributes

Attributes are stored in a HashMap with string keys. Attribute values can be either String values or a boolean true:

use dompa::{Node, NodeAttributeValue};
use std::collections::HashMap;

let mut attrs = HashMap::new();
// String attribute
attrs.insert(String::from("href"), NodeAttributeValue::string("#top"));
// Boolean attribute (present without value)
attrs.insert(String::from("required"), NodeAttributeValue::True);

let anchor = Node::block("a", attrs, vec![Node::text("Go to top")]);

Dompa provides a convenient helper method for string attributes:

// Instead of:
NodeAttributeValue::String(String::from("value"))

// You can use:
NodeAttributeValue::string("value")