swc-project/swc

Rust-based platform for the Web

Make the web (development) faster.

SWC (stands for Speedy Web Compiler) is a super-fast TypeScript / JavaScript compiler written in Rust. It's a library for Rust and JavaScript at the same time. If you are using SWC from Rust, see rustdoc and for most users, your entry point for using the library will be parser.

Also, SWC tries to ensure that

If you select the latest version of each crates, it will work

for rust users.

MSRV of crates is currently 1.71.

To update all SWC crates you use, you can run curl https://raw.githubusercontent.com/swc-project/swc/main/scripts/update-all-swc-crates.sh | bash -s. This script will update all dependencies to the latest version and run cargo build to ensure that everything works. Note that you need

• jq
• cargo upgrade

command to run the script.

---

If you are using SWC from JavaScript, please refer to docs on the website.

Documentation

Check out the documentation in the website.

Features

Please see comparison with babel.

Performance

Please see benchmark results on the website.

Supporting swc

SWC is a community-driven project, and is maintained by a group of volunteers. If you'd like to help support the future of the project, please consider:

• Giving developer time on the project. (Message us on Discord (preferred) or Github discussions for guidance!)
• Giving funds by becoming a sponsor (see https://opencollective.com/swc)!

Contributing

See CONTRIBUTING.md. You may also find the architecture documentation useful (ARCHITECTURE.md).

License

SWC is primarily distributed under the terms of the Apache License (Version 2.0).

See LICENSE for details.

swc's Issues

JSX pragma

One of the recent commits added support for jsx but as far as I see it did so without support for @jsx pragma documented here: https://babeljs.io/docs/en/babel-plugin-transform-react-jsx#custom-1)

This is critical for people using https://emotion.sh/ in their projects.

So this issue here is to request this feature 🙂

Support for decorators

Much like https://babeljs.io/docs/en/babel-plugin-proposal-decorators

Great project!

Bug: swc does not import the `_interopRequireDefault` function when it is referenced

If you try compiling the following with swc:

import Foo from 'bar';

You get this:

'use strict';
var _bar = _interopRequireDefault(require('bar'));

The function _interopRequireDefault is referenced, though never defined, leading to ReferenceErrors.

There are other functions that have the same behavior:

• _interopRequireWildcard

Expected: If swc inserts references to functions, it will define or import those functions.

Actual: swc references numerous functions that it does not define/import.

Something like @babel/preset-env

caniuse-db for rust: https://github.com/kdy1/rust-caniuse

Required transformations

• regenerator

Arc<Helpers> is wrong

Injected helpers should not flow into other files.

Current behavior

input.js:

class Foo extends Bar {}

simple.js:

npx swc -d out *.js

make out/simple.js contain unnecessary helpers.

I'll fix this ASAP.

Missing comma when importing both default and named imports in single declaration

Comma is missing when importing both default and named imports in single declaration:

Input

$ cat test.js
import colors, { color } from 'patterns/colors'

Output

$ node_modules/.bin/swc test.js
import colors { color }from 'patterns/colors';

Expected

$ node_modules/.bin/swc test.js
import colors, { color }from 'patterns/colors';

$ cat node_modules/swc/package.json
{
  "name": "swc",
  "version": "1.0.3",

css support

TODOs

• Parser
• Transforms (See postcss)
  • minifier (P-high)
  • cssnext (P-high)
    This includes features which does not have compatability hazard.
  • AutoPrefixer (P-high)
• scss support
  It might use libsass.

Bug: swc incorrectly un-strings object keys with periods in them

Try running swc on the following js:

const x = {
  'foo.bar': true
}

It will output

'use strict';
var x = {
        foo.bar: true
};

The foo.bar is not correct syntax. swc needs to keep string object keys that contain js special characters as strings. It's probably easier to just keep all string object keys as strings.

EcmaScript lexer is inefficient

• It currently pushes one char at a time. It should chunk to amortize allocations.

Current code is similar to

let mut buf = String::new();
loop {
   // xxx
   buf.push(c);
}

Obviously, this almost always allocate and reallocates quite frequently.

---

• It allocate needlessly while tokenizing numeric literals.

Noticeable parts are

let s = format!("{}", val);
// if it contains '8' or '9', it's decimal.
if s.contains('8') || s.contains('9') {}

// It's Legacy octal, and we should reinterpret value.
let val = u64::from_str_radix(&format!("{}", val), 8)
    .expect("Does this can really happen?");
let val = format!("{}", val)
    .parse()
     .expect("failed to parse numeric value as f64");

val = format!("{}.{}", val, minority).parse();

tagged template literal can contain invalid escape sequence

parser currently does not support parsing code like

latex`\unicode`

Note: this is valid only for es2018+
Implementor should check for the JscTarget.

This can be done by modifying code at

swc/ecmascript/parser/src/lexer/mod.rs

Lines 927 to 991 in 53b09aa

	fn read_tmpl_token(&mut self, start_of_tpl: BytePos) -> LexResult<Token> {
	let start = self.cur_pos();
	// TODO: Optimize
	let mut has_escape = false;
	let mut cooked = String::new();
	let mut raw = String::new();
	while let Some(c) = self.cur() {
	if c == '`' || (c == '$' && self.peek() == Some('{')) {
	if start == self.cur_pos() && self.state.last_was_tpl_element() {
	if c == '$' {
	self.bump();
	self.bump();
	return Ok(tok!("${"));
	} else {
	self.bump();
	return Ok(tok!('`'));
	}
	}
	// TODO: Handle error
	return Ok(Template {
	cooked: cooked.into(),
	raw: raw.into(),
	has_escape,
	});
	}
	if c == '\\' {
	has_escape = true;
	raw.push('\\');
	let mut wrapped = Raw(Some(raw));
	let ch = self.read_escaped_char(&mut wrapped)?;
	raw = wrapped.0.unwrap();
	if let Some(s) = ch {
	cooked.extend(s);
	}
	} else if c.is_line_break() {
	self.state.had_line_break = true;
	let c = if c == '\r' && self.peek() == Some('\n') {
	raw.push_str("\\r\\n");
	self.bump(); // '\r'
	'\n'
	} else {
	match c {
	'\n' => raw.push_str("\n"),
	'\r' => raw.push_str("\r"),
	'\u{2028}' => raw.push_str("\u{2028}"),
	'\u{2029}' => raw.push_str("\u{2029}"),
	_ => unreachable!(),
	}
	c
	};
	self.bump();
	cooked.push(c);
	} else {
	self.bump();
	cooked.push(c);
	raw.push(c);
	}
	}
	self.error(start_of_tpl, SyntaxError::UnterminatedTpl)?
	}

Where's the code for the javascript package?

I think it's necessary to link this in some places. I can't find it for the life of me and I want to contribute to the project!

Dynamic import

I'd love to try this library out for Mastodon, to see if it helps with compile time, but currently I'm stuck on dynamic import() calls throwing an error.

Automate release & Precompiled binary

Binary (index.node) should be built on ci and package's install script should download proper built dylib from github releases.

TODOs

• Build index.node from ci
  Note: neon does not support cross compilation

• install script to download proper binary

`.swcrc` should allow using typescript and javascript together

Currently you can't use esnext features if you use typescript.

String literal as property name not handled correctly

Hi, I've encountered a problem using swc in one of my code-bases. Feel free to close if this is known or symptomatic of an planned but unjmplemented feature.

Given this source javascript:

const o = {
    foo: 1,
    'bar@': 2,
    '@': 3
};

Expected output:

var o = {
    foo: 1,
    'bar@': 2,
    '@': 3
};

Actual output:

var o = {
    foo: 1,
    bar@: 2,
    @: 3
};

Which results in an SyntaxError: Invalid or unexpected token for @.

I am using:

$ npx swc --version
0.1.7

Which incidentally appears to be another problem since package.json is pinned to 0.1.8:

"dependencies": {
    "swc": "^1.0.3",
    "swc-cli": "^0.1.8"
  }

Online repl

ratel-rust have one, and it looks great

Usage without node.js

Is it possible to use swc from rust directly?

We're building https://github.com/superfly/fly.rs and would like to bundle code (typescript and javascript) via swc.

As far as I can tell, the node implementation is a wrapper around swc, but it should work from rust too, right?

Legacy octal escape is not permitted in strict mode

HI,

I'm getting this error when trying to compile a few test files :

C:\...>npx -p swc -p swc-cli swc *.js -o out.js
error: Legacy octal escape is not permitted in strict mode
 --> <GLOBAL.Path>:1:45
  |
1 | 'C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000;C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;C:\windows\system32;C:\windows;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;
C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\In
tel(R) Management Engine Components\IPT;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files\Git\cmd;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\S
ystem32\OpenSSH\;C:\Program Files (x86)\Yarn\bin\;C:\Program Files\Java\jdk-11.0.1\bin;C:\Program Files (x86)\Calibre2\;C:\Program Files\nodejs\;C:\Users\vrs\AppData\Local\Microsoft\WindowsApps;C:\Users\vrs\AppData\Local\Programs\Mi
crosoft VS Code\bin;C:\Users\vrs\AppData\Roaming\npm;C:\Users\vrs\bin\Sencha\Cmd;'
  |                                             ^^

Error: internal error in Neon module: failed to parse global variable Path=`'C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000;C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;C:\windows\system32;C:\windo
ws;C:\windows\System32\Wbem;C:\windows\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\I
ntel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files\Git\cmd;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOW
S\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\WINDOWS\System32\OpenSSH\;C:\Program Files (x86)\Yarn\bin\;C:\Program Files\Java\jdk-11.0.1\bin;C:\Program Files (x86)\Calibre2\;C:\Program Files\nodejs\;C:\Users\vrs\Ap
pData\Local\Microsoft\WindowsApps;C:\Users\vrs\AppData\Local\Programs\Microsoft VS Code\bin;C:\Users\vrs\AppData\Roaming\npm;C:\Users\vrs\bin\Sencha\Cmd;'` as module
    at Object.transformFileSync (C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc\lib\index.js:15:43)
    at Promise (C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\util.js:68:32)
    at new Promise (<anonymous>)
    at Object.compile (C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\util.js:66:12)
    at C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\file.js:155:47
    at Generator.next (<anonymous>)
    at C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\file.js:7:71
    at new Promise (<anonymous>)
    at __awaiter (C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\file.js:3:12)
    at C:\Users\vrs\AppData\Roaming\npm-cache\_npx\7000\node_modules\swc-cli\lib\src\file.js:148:28

Thanks in advance

'SPDY' confusing.

Hi, sorry to raise an issue about something unimportant like this, but I think having 'SPDY' in the name is a bit confusing. I thought it was related to the protocol developed by Google.

Maybe it could just be 'speedy'?

Bundler

Status

• Bundling of es6 modules.
  • normal import
  • aliased import
  • namespaced import
    • de-globing (& tree shaking)
    • namespaced import with dynamic key
• Tree shaking.
• Resolve / Load` trait for extensibility
• Chunking
• Dynamic imports
  • Loading
• swc integration
  • Simple optimizations
  • Transform
  • Optimize helpers (remove duplicate)
  • .swcrc integration
• "esnext" in package.json
• spack.config.js

This is a very hard part. I'm considering moving the source code of node-swc to this repository.

• codegen: Multiple SourceFile

This is required to create the correct source map.

• Bundling of non-js assets

Need to determine plugin api.

Error reporting

I don't know which features are required.

Maybe..

• Code highlight like rustc?

TypeScript

Will this transpiler be up to date with the newest changes to TS when they occur?

Awesome project btw!

Possibility of compiling on stable Rust?

Hello! Over in the wasm-bindgen project we've got a new proposal which partly entails eventually having a JS parser built into our tooling. The JS parser would need to basically compile ES module syntax to either CommonJS or "linked manually with no modules" style syntax. The swc project seems like it perfectly fits the bill in terms of use cases here!

One hesitation that we'd currently have from using swc is that it looks like it currently requires nightly Rust and also isn't published much on crates.io. I'm curious if y'all have an idea about whether it's feasible in the near-term to compile on stable (and as a bit of a stretch goal publish on crates.io too). That'd make swc a strong possibility for us to use in wasm-bindgen as a dependency!

We're mostly just evaluating our options right now, so "not any time soon" is a totally valid answer too!

Hello World example code or boilerplate

• do you any boilerplate or a hello world example code to play around this

Bug: Ternary operator doesn't work inside parentheses in Typescript

swc fails to compile ternary operators inside parentheses when TypeScript is used:

(foo ? 1 : 2);

$ swc test.ts
error: Unexpected token Some(Colon)
 --> test.ts:1:10
  |
1 | (foo ? 1 : 2);
  |          ^

fatal runtime error: failed to initiate panic, error 5
Abort trap: 6

.swcrc

{
  "jsc": {
    "parser": {
      "syntax": "typescript"
    }
  }
}

$ swc --version
0.1.7
# Yarn reports packages as `[email protected]` and `[email protected]`

The same code compiles fine if "ecmascript" is used instead.

$ swc test.js
foo ? 1 : 2;

How to build with cargo?

Hi
After checkout:
I get this error trying to build swc:
cargo build --release --all-features
error: failed to parse manifest at /tmp/guix-build-swc-0.0-1.2e22397f4.drv-7/source/ecmascript/ast/Cargo.toml

Caused by:
editions are unstable

Caused by:
feature edition is required

this Cargo does not support nightly features, but if you
switch to nightly channel you can add
cargo-features = ["edition"] to enable this feature

Proper Documentation for Migrating from Babel to SWC

Is there any documentation or help on getting Babel replaced with SWC. I wanted to try out SWC to check its performance against Babel.

I could only got till npm installation of SWC and RustUP for windows. But the doc at https://swc-project.github.io/4_migrating_from_babel.html is blank.

Unignore "431ecef8c85d4d24.js" and "8386fbff927a9e0e.js".

"431ecef8c85d4d24" is about unicode xid vs unicode id.

I doubt that character is used for identifier in practice.

"8386fbff927a9e0e" is about parsing very long numeric literal.

It's about float parsing issue. ignored test and P-low because I don't think someone would type 30 zeros instead of 1e30.

CONTRIBUTING.md and ARCHITECTURE.md are missing

The README says:

See CONTRIBUTING.md. You may also find the architecture documentation useful (ARCHITECTURE.md).

But these files are not in the repository.

Internal documentations

• Use rustdoc for internal documents.
  • #[derive(AstNode)] derives FoldWith to bypass a rust bug.

Documentation for binary / library is postponed because it should be how-to-use example, and binary is required to do that.

Loaders for several module bundlers

I want to create loaders for SWC for several bundlers. I might ask someone to do it instead, but basically:

• Rollup
• Webpack Just noticed it's done

Should I create the modules for these, or will you?

TypeScript support for type-checking

I've successfully used swc to compile typescript files, that's great. I'm thoroughly impressed!

However, I noticed it compiled "wrong" typescript. Example:

function foo(): string {
}

^ is invalid typescript (the function actually returns void), but this will still compile fine with swc.

I'm assuming this is a lot more complicated to make happen. You'd have to check keep track of the type signature of every function and variables to compare and check type validity.

Is it possible target llvm like this PR in prepack?

Is it possible target llvm like this PR in prepack?
LLVM Backend

Optimize arguments

use(8 + 8) should be use(16)
But I don't know why it is not optimized.

Clean up

• Sort arguments of assert_eq call.
• Replace uses of self.input.xx() to xx!() (in lexer).
• Document should be consistent.
• Lexer should use Unicode ID instead of Unicode XID.

Source map

EcmaScript AST needs some design work

• Unary operators are always prefix.

estree/estree#118

commonjs transformation not working via JS API

swc does not transform ES6 import syntax into a require() call when invoked via the JS API. (node bindings)

Reproduction

npm install swc and then:

console.log(
  require('swc').transformSync(`
    import {lodash} from 'lodash'
  `, {
    module: {
      type: 'commonjs'
    }
  }).code
);

Outputs:

import { lodash }from 'lodash';

TypeScript support

TODOs

• Parser

Handle comment

It's stripped out by lexer at the moment

Better codegen

Currently code generator can not print pretty code neither minified code.
It should support both. (Maybe)

Description of repository is misleading

Under the title of the repository navigation it says:

Super-fast alternative for babel

But within the README it says:

swc is rust port of babel and closure compiler.

Surely under the navigation (the first thing people see) should also mimic what the repository README states?

Handle early errors in ecmascript parser

And enable early/fail tests from test262-parser-tests.

• (Optional) Check for unmatched labels and recover from it

This can be done by storing current labels in the parser and checking if it matches.

This should be optional as it may degrade performance.
(e.g. deno may not require such feature as they run the javascript file right away)

wasm?

Could this potentially be compiled to WebAssembly? This would allow full interop with the existing Babel packages, and would truly thrust this project into the spotlight.

Question about emitter attribute

Hi there,

This is a non-urgent question about the emitter attribute. I'm not too familiar with rust and I'm trying to understand what this code block is doing, and why it's necessary:

#[allow(unreachable_code)]
{
    return Ok(());
}

Could you explain it to me?

Thank you for the interesting project. Very excited to see where it goes!

Export ast / parser as a separate crate

Plugin system

Error when running benchmark from node-swc

bench-runner:

Error in :transform:swc
Error: Error(Msg("missing field `react`"), State { next_error: None, backtrace: None })

node: v10.15.0
rustc: 1.33.0-nightly (b2b7a063a 2019-01-01)

Please help :)

Some corner case

When I tried to compile lodash with swc, I found some problems.

ERROR in ./vendor/escape.js 2:8
Module parse failed: Unexpected token (2:8)
You may need an appropriate loader to handle this file type.
| var htmlEscapes = {
>         &: '&amp',
|         <: '&lt',
|         >: '&gt',
 @ ./src/lodash.js 43:0-38 294:16-22
 @ ./src/test.js
 @ multi ./src/test.js

ERROR in ./vendor/unescape.js 2:8
Module parse failed: Unexpected token (2:8)
You may need an appropriate loader to handle this file type.
| var htmlUnescapes = {
>         &amp;: '&',
|         &lt;: '<',
|         &gt;: '>',
 @ ./src/lodash.js 225:0-42 476:18-26
 @ ./src/test.js
 @ multi ./src/test.js

ERROR in ./vendor/.internal/Stack.js 46:32
Module parse failed: Unexpected token (46:32)
You may need an appropriate loader to handle this file type.
|         }, {
|                 key: 'delete',
>                 value: function delete(key) {
|                     var data = this.__data__;
|                     var result = data['delete'](key);
 @ ./vendor/.internal/baseClone.js 4:0-31 139:26-31
 @ ./vendor/clone.js
 @ ./src/lodash.js
 @ ./src/test.js
 @ multi ./src/test.js

ERROR in ./vendor/.internal/MapCache.js 58:32
Module parse failed: Unexpected token (58:32)
You may need an appropriate loader to handle this file type.
|         }, {
|                 key: 'delete',
>                 value: function delete(key) {
|                     var result = getMapData(this, key)['delete'](key);
|                     this.size -= result ? 1 : 0;
 @ ./vendor/.internal/SetCache.js 22:0-37 29:28-36
 @ ./vendor/.internal/baseDifference.js
 @ ./vendor/difference.js
 @ ./src/lodash.js
 @ ./src/test.js
 @ multi ./src/test.js

About reserved words, babel will add an underscore to the front, like

{
    key: 'delete',
    value: function _delete(key) {
      var result = getMapData(this, key)['delete'](key);
      this.size -= result ? 1 : 0;
      return result;
}

This project is very cool and I am looking forward to the plugin system.

jsx support