svelte-syntax

A Rust crate for parsing Svelte components into typed AST and CST representations.

svelte-syntax handles the syntax layer only — it parses .svelte files and CSS stylesheets into inspectable tree structures. It does not compile components into JavaScript or CSS. For compilation, use svelte-compiler.

Install

[dependencies]
svelte-syntax = "0.1.4"

Quick start

Parse a Svelte component into the modern AST (Svelte 5 runes mode):

use svelte_syntax::{parse, ParseMode, ParseOptions};

let doc = parse(
    "<script>let count = 0;</script><button>{count}</button>",
    ParseOptions {
        mode: ParseMode::Modern,
        ..ParseOptions::default()
    },
)?;

let root = match doc.root {
    svelte_syntax::ast::Root::Modern(root) => root,
    _ => unreachable!(),
};

assert!(root.instance.is_some());
assert!(!root.fragment.nodes.is_empty());
# Ok::<(), svelte_syntax::CompileError>(())

Parse raw source into a tree-sitter CST:

use svelte_syntax::{SourceId, SourceText, parse_svelte};

let source = SourceText::new(SourceId::new(0), "<div>hello</div>", None);
let cst = parse_svelte(source)?;

assert_eq!(cst.root_kind(), "document");
assert!(!cst.has_error());
# Ok::<(), svelte_syntax::CompileError>(())

What it provides

AST parsing

parse — parse a component into a Document containing a modern (Svelte 5 runes) or legacy (Svelte 3/4) AST root.
parse_modern_root — parse directly into a modern::Root with typed script, template, and style blocks.
parse_modern_root_incremental — reparse using a previous AST and CST, reusing unchanged subtrees for speed.
parse_css — parse a standalone CSS stylesheet.

CST parsing

parse_svelte — parse source into a tree-sitter concrete syntax tree for low-level inspection.
parse_svelte_incremental — incremental reparse using a previous tree and a CstEdit.
CstParser — configurable tree-sitter parser with language selection.

JavaScript handles

JsProgram — a parsed JavaScript/TypeScript program. Owns its source so you can access the AST without reparsing.
JsExpression — same idea for a single JS/TS expression.

Arena AST

SvelteAst — arena-allocated AST with stable node IDs, parent pointers, and position queries. Designed for language servers, linters, and formatters that need fast navigation and incremental updates.

Utilities

SourceText — borrowed source text with filename, UTF-16 offset conversion, and line/column lookups.
BytePos, Span, SourceId — lightweight position primitives.
Element and attribute classification helpers: classify_element_name, classify_attribute_name, is_component_name, is_void_element_name, and others.
CompileError — structured error type with source positions and diagnostic codes.

License

MIT

svelte-syntax 0.1.5