b1a4cc044d
`Parser::parse` returns `Option<&Tree>`. An `unwrap()` or similar is required to get the actual `Tree`.
98 lines
2.8 KiB
Markdown
98 lines
2.8 KiB
Markdown
Rust Tree-sitter
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================
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[](https://travis-ci.org/tree-sitter/tree-sitter)
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[](https://ci.appveyor.com/project/maxbrunsfeld/tree-sitter/branch/master)
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[](https://crates.io/crates/tree-sitter)
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Rust bindings to the [Tree-sitter][] parsing library.
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### Basic Usage
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First, create a parser:
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```rust
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use tree_sitter::{Parser, Language};
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// ...
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let mut parser = Parser::new();
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```
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Then assign a language to the parser. Tree-sitter languages consist of generated C code. To use them from rust, you must declare them as `extern "C"` functions and invoke them with `unsafe`:
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```rust
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extern "C" { fn tree_sitter_c() -> Language; }
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extern "C" { fn tree_sitter_rust() -> Language; }
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extern "C" { fn tree_sitter_javascript() -> Language; }
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let language = unsafe { tree_sitter_rust() };
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parser.set_language(language).unwrap();
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```
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Now you can parse source code:
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```rust
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let source_code = "fn test() {}";
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let tree = parser.parse(source_code, None).unwrap();
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let root_node = tree.root_node();
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assert_eq!(root_node.kind(), "source_file");
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assert_eq!(root_node.start_position().column, 0);
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assert_eq!(root_node.end_position().column, 12);
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```
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### Editing
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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:
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```rust
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let new_source_code = "fn test(a: u32) {}"
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tree.edit(InputEdit {
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start_byte: 8,
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old_end_byte: 8,
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new_end_byte: 14,
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start_position: Point::new(0, 8),
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old_end_position: Point::new(0, 8),
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new_end_position: Point::new(0, 14),
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});
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let new_tree = parser.parse(new_source_code, Some(&tree));
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```
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### Text Input
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The source code to parse can be provided either 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:
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```rust
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// Store some source code in an array of lines.
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let lines = &[
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"pub fn foo() {",
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" 1",
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"}",
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];
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// Parse the source code using a custom callback. The callback is called
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// with both a byte offset and a row/column offset.
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let tree = parser.parse_with(&mut |_byte: u32, position: Point| -> &[u8] {
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let row = position.row as usize;
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let column = position.column as usize;
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if row < lines.len() {
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if column < lines[row].as_bytes().len() {
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&lines[row].as_bytes()[column..]
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} else {
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"\n".as_bytes()
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}
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} else {
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&[]
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}
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}, None).unwrap();
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assert_eq!(
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tree.root_node().to_sexp(),
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"(source_file (function_item (visibility_modifier) (identifier) (parameters) (block (number_literal))))"
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);
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```
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[tree-sitter]: https://github.com/tree-sitter/tree-sitter
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