EcmaScript/TypeScript parser for the rust programming language.

Features

Heavily tested

Passes almost all tests from tc39/test262.

Error reporting

error: 'implements', 'interface', 'let', 'package', 'private', 'protected',  'public', 'static', or 'yield' cannot be used as an identifier in strict mode
--> invalid.js:3:10
|
3 | function yield() {
|          ^^^^^

Error recovery

The parser can recover from some parsing errors. For example, parser returns Ok(Module) for the code below, while emitting error to handler.

const CONST = 9000 % 2;
const enum D {
// Comma is required, but parser can recover because of the newline.
d = 10
g = CONST
}

Example (lexer)

See lexer.rs in examples directory.

Example (parser)

#[macro_use]
extern crate swc_common;
extern crate swc_ecma_parser;
use swc_common::sync::Lrc;
use swc_common::{
errors::{ColorConfig, Handler},
FileName, FilePathMapping, SourceMap,
};
use swc_ecma_parser::{lexer::Lexer, Parser, StringInput, Syntax};

fn main() {
let cm: Lrc<SourceMap> = Default::default();
let handler =
Handler::with_tty_emitter(ColorConfig::Auto, true, false,
Some(cm.clone()));

// Real usage
// let fm = cm
//     .load_file(Path::new("test.js"))
//     .expect("failed to load test.js");
let fm = cm.new_source_file(
FileName::Custom("test.js".into()).into(),
"function foo() {}".into(),
);
let lexer = Lexer::new(
// We want to parse ecmascript
Syntax::Es(Default::default()),
// EsVersion defaults to es5
Default::default(),
StringInput::from(&*fm),
None,
);

let mut parser = Parser::new_from(lexer);

for e in parser.take_errors() {
e.into_diagnostic(&handler).emit();
}

let _module = parser
.parse_module()
.map_err(|mut e| {
// Unrecoverable fatal error occurred
e.into_diagnostic(&handler).emit()
})
.expect("failed to parser module");
}

Cargo features

typescript

Enables typescript parser.

verify

Verify more errors, using swc_ecma_visit.

Known issues

Null character after \

Because [String] of rust should only contain valid utf-8 characters while javascript allows non-utf8 characters, the parser stores invalid utf8 characters in escaped form.

As a result, swc needs a way to distinguish invalid-utf8 code points and input specified by the user. The parser stores a null character right after \\ for non-utf8 code points. Note that other parts of swc is aware of this fact.

Note that this can be changed at anytime with a breaking change.