e845131e03
Summary: Release notes: none Currently, when don't really fully deal with abstract conditions fully throughout the Prepack codebase and we usually simply leak/emit a temporal to get around them. So this PR aims at tackling many of the code-sites where they are prevalent by using the internal React bundle to find most of them and address them – with the goal of improving evaluation in cases where we run into conditionals. With this PR, we now try and resolve different parts of the condition, including conditionals such as `||` and `&&`. This allows us to evaluate potentially far more than before when it comes to product code where we inhabit many deep conditionals. These changes also impact `Object.assign` as it triggered an invariant with `getSnapshot` as it never expected a conditional there. This should also fix https://github.com/facebook/prepack/issues/2323. I've added some tests to show this but here is an example of the output before and after: ```js // Input function fn(x, b) { var a = x ? b : { a: 2 }; return a.a; } // Before var _2 = function (x, b) { var _3 = {}; _3.a = 2; var _$0 = (x ? b : _3).a; return _$0; }; // After var _2 = function (x, b) { if (x) { var _$0 = b.a; } return x ? _$0 : 2; }; ``` For conditional `Object.assign`, the output looks like this (note: we need materializing rather than leaking to better improve the output): ```js // Input function fn(x) { var a = x ? { a: 1 } : { a: 2 }; return Object.assign({}, a, { b: 1 }); } // Before var _2 = function (x) { var _$0 = { a: 1 }; var _$1 = { a: 2 }; ({}).a = 1; ({}).a = 2; var _$2 = { b: 1 }; var _9 = {}; var _$3 = _$9(_9, x ? _$0 : _$1, _$2); return _9; }; // After var _2 = function (x) { return { a: x ? 1 : 2, b: 1 }; }; ``` I also took the time to apply the same small changes to the existing code in `CallExpression` so the logic there could also handle `&&` and `||` cases too. Including is a React test that shows that we can now inline a component that we previously weren't able to do. Pull Request resolved: https://github.com/facebook/prepack/pull/2503 Differential Revision: D9616500 Pulled By: trueadm fbshipit-source-id: 3888a62da330c64b0395723f8764c3590adc8491 |
||
|---|---|---|
| .circleci | ||
| assets | ||
| bin | ||
| fb-www | ||
| flow-libs | ||
| flow-typed/npm | ||
| fuzzer | ||
| scripts | ||
| src | ||
| test | ||
| website | ||
| .eslintignore | ||
| .eslintrc | ||
| .flowconfig | ||
| .gitignore | ||
| .gitmodules | ||
| .prettierrc | ||
| .watchmanconfig | ||
| babel.config.js | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| LICENSE | ||
| package.json | ||
| PATENTS | ||
| README.md | ||
| webpack.config.js | ||
| yarn.lock | ||
Prepack 
Prepack is a partial evaluator for JavaScript. Prepack rewrites a JavaScript bundle, resulting in JavaScript code that executes more efficiently. For initialization-heavy code, Prepack works best in an environment where JavaScript parsing is effectively cached.
See the official prepack.io website for an introduction and an interactive REPL playground.
How to use Prepack
Install the CLI via npm,
$ npm install -g prepack
Or if you prefer yarn, make sure you get yarn first,
$ npm install -g yarn
and then install the Prepack CLI via yarn:
$ yarn global add prepack
You may need to prepend (pun intended!) the command with sudo in some cases.
Let the party begin
To compile a file and print the output to the console:
$ prepack script.js
If you want to compile a file and output to another file:
$ prepack script.js --out script-processed.js
Detailed instructions and the API can be found at Prepack CLI: Getting Started
Plugins to other tools
The following are a few plugins to other tools. They have been created and are maintained separately from Prepack itself. If you run into any issues with those plugins, please ask the plugin maintainers for support.
- A Rollup plugin for Prepack
- A Webpack plugin for Prepack
- A Parcel plugin for Prepack
- A Visual Studio code plugin for Prepack
- A babel plugin which transforms Flow annotations into prepack model declarations.
Status
- test262 status on master branch
- code coverage report for serialization tests
- To see the status for a pull request, look for the message All checks have passed or All checks have failed. Click on Show all checks, Details, Artifacts, and then test262-status.txt or coverage-report-sourcemapped/index.html.
How to get the code
- Clone repository and make it your current directory.
git submodule initgit submodule update --init- Get yarn and node, then do
yarn
Note: For development work you really need yarn, as many scripts require it.
How to build, lint, type check
- Get the code
yarn build
You can later runyarn watchin the background to just compile changed files on the fly.yarn lintyarn flow
How to run tests
- Get the code
- Make sure the code is built, either by running
yarn buildoryarn watch yarn test
You can run individual test suites as follows:
yarn test-serializer
This tests the interpreter and serializer. All tests should pass.yarn test-test262
This tests conformance against the test262 suite. Not all will pass, increasing conformance is work in progress.
How to run the interpreter
- Get the code
- Make sure the code is built, either by running
yarn buildoryarn watch yarn repl
This starts an interactive interpreter session.
How to run Prepack
-
Get the code
-
Make sure the code is built, either by running
yarn buildoryarn watch. -
Have a JavaScript file handy that you want to prepack, for example:
echo "function hello() { return 'hello'; } function world() { return 'world'; } s = hello() + ' ' + world();" >/tmp/sample.js -
cat /tmp/sample.js | yarn prepack-cli
Try--helpfor more options.
How to validate changes
Instead of building, linting, type checking, testing separately, the following does everything together:
yarn validate
How to edit the website
The content for prepack.io resides in the website directory of this repository. To make changes, submit a pull request, just like for any code changes.
In order to run the website locally at localhost:8000:
- Build prepack into the website:
yarn build && mv prepack.min.js website/js - Run
python -m SimpleHTTPServer(Python 2) orpython -m http.server(Python 3) from thewebsite/directory
How to contribute
To read more about the project, check out this suggested reading wiki
For more information about contributing pull requests and issues, see our Contribution Guidelines.
License
Prepack is BSD-licensed. We also provide an additional patent grant.