Crate swc_ecma_parser

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.

Modules

error

input

lexer

ECMAScript lexer.

token

Ported from babel/babylon

Structs

Capturing

Note: Lexer need access to parser’s context to lex correctly.

Context

Syntactic context.

EsSyntax

Parser

EcmaScript parser.

StringInput

Implementation of Input.

TokensInput

TsSyntax

Enums

Syntax

Traits

Input

Tokens

Clone should be cheap if you are parsing typescript because typescript syntax requires backtracking.

Functions

parse_file_as_expr

Note: This is recommended way to parse a file.

parse_file_as_module

Note: This is recommended way to parse a file.

parse_file_as_program

Note: This is recommended way to parse a file.

parse_file_as_script

Note: This is recommended way to parse a file.

with_file_parser

Type Aliases

PResult

When error occurs, error is emitted and parser returns Err(()).