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# Rust Tree-sitter
[![crates.io badge]][crates.io]
[crates.io]: https://crates.io/crates/tree-sitter
[crates.io badge]: https://img.shields.io/crates/v/tree-sitter.svg?color=%23B48723
Rust bindings to the [Tree-sitter][] parsing library.
## Basic Usage
First, create a parser:
```rust
use tree_sitter::{InputEdit, Language, Parser, Point};
let mut parser = Parser::new();
```
Add the `cc` crate to your `Cargo.toml` under `[build-dependencies]`:
```toml
[build-dependencies]
cc="*"
```
Then, add a language as a dependency:
```toml
[dependencies]
tree-sitter = "0.24"
tree-sitter-rust = "0.23"
```
To then use a language, you assign them to the parser.
```rust
parser.set_language(&tree_sitter_rust::LANGUAGE.into()).expect("Error loading Rust grammar");
```
Now you can parse source code:
```rust
let source_code = "fn test() {}";
let mut tree = parser.parse(source_code, None).unwrap();
let root_node = tree.root_node();
assert_eq!(root_node.kind(), "source_file");
assert_eq!(root_node.start_position().column, 0);
assert_eq!(root_node.end_position().column, 12);
```
### Editing
Once you have a syntax tree, you can update it when your source code changes.
Passing in the previous edited tree makes `parse` run much more quickly:
```rust
let new_source_code = "fn test(a: u32) {}";
tree.edit(&InputEdit {
start_byte: 8,
old_end_byte: 8,
new_end_byte: 14,
start_position: Point::new(0, 8),
old_end_position: Point::new(0, 8),
new_end_position: Point::new(0, 14),
});
let new_tree = parser.parse(new_source_code, Some(&tree));
```
### Text Input
The source code to parse can be provided either as a string, a slice, a vector,
or as a function that returns a slice. The text can be encoded as either UTF8 or UTF16:
```rust
// Store some source code in an array of lines.
let lines = &[
"pub fn foo() {",
" 1",
"}",
];
// Parse the source code using a custom callback. The callback is called
// with both a byte offset and a row/column offset.
let tree = parser.parse_with(&mut |_byte: usize, position: Point| -> &[u8] {
let row = position.row as usize;
let column = position.column as usize;
if row < lines.len() {
if column < lines[row].as_bytes().len() {
&lines[row].as_bytes()[column..]
} else {
b"\n"
}
} else {
&[]
}
}, None).unwrap();
assert_eq!(
tree.root_node().to_sexp(),
"(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (number_literal))))"
);
```
[tree-sitter]: https://github.com/tree-sitter/tree-sitter
## Features
- **std** - This feature is enabled by default and allows `tree-sitter` to use the standard library.
- Error types implement the `std::error:Error` trait.
- `regex` performance optimizations are enabled.
- The DOT graph methods are enabled.
- **wasm** - This feature allows `tree-sitter` to be built for Wasm targets using the `wasmtime-c-api` crate.
|
