Flow
Flow is a static typechecker for JavaScript. To find out more about Flow, check out flow.org.
Contents
- Requirements
- Using Flow
- Using Flow's parser from JavaScript
- Building Flow from source
- Join the Flow community
- License
Requirements
Flow works with:
- macOS (x86_64)
- Linux (x86_64 and arm64)
- Windows (x86_64, Windows 10 recommended)
There are binary distributions for each of these platforms and you can also build it from source on any of them as well.
Using Flow
Check out the installation instructions, and then the usage docs.
Using Flow's parser from JavaScript
While Flow is written in OCaml, its parser is available as a compiled-to-JavaScript module published to npm, named flow-parser. Most end users of Flow will not need to use this parser directly, but JavaScript packages which make use of parsing Flow-typed JavaScript can use this to generate Flow's syntax tree with annotated types attached.
Building Flow from source
Flow is written in OCaml (OCaml 4.14.0 is required).
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Install system dependencies:
-
Mac:
brew install opam -
Debian:
sudo apt-get install opam -
Other Linux: see opam docs
-
Windows: cygwin and a number of dependencies like
make,gccandg++are required.One way to install everything is to install Chocolatey and then run
.\scripts\windows\install_deps.ps1and.\scripts\windows\install_opam.ps1. Otherwise, see the "Manual Installation" section of OCaml for Windows docs and install all of the packages listed in ourinstall_deps.ps1.The remainder of these instructions should be run inside the Cygwin shell:
C:\tools\cygwin\Cygwin. Thencd /cygdrive/c/Users/you/path/to/checkout.
-
-
Validate the
opamversion is2.x.x:opam --version
The following instructions expect
2.x.x. Should your package manager have installed a1.x.xversion, please refer to the opam docs to install a newer version manually. -
Initialize
opam:# on Mac and Linux: opam init # on Windows: scripts/windows/init_opam.sh
-
Install Flow's OCaml dependencies:
# from within this git checkout make depsnote: If you find that you get an error looking for
ocaml-base-compilerversion, your local dependency repo may be out of date and you need to runopam update+opam upgrade -
Build the
flowbinary:eval $(opam env) make
This produces the
bin/flowbinary. -
Build
flow.js(optional):opam install -y js_of_ocaml.5.5.2 make js
This produces
bin/flow.js.The Flow parser can also be compiled to JavaScript. Read how here.
Running the tests
To run the tests, first compile flow using make. Then run bash ./runtests.sh bin/flow
There is a make test target that compiles and runs tests.
To run a subset of the tests you can pass a second argument to the runtests.sh file.
For example: bash runtests.sh bin/flow class | grep -v 'SKIP'
Join the Flow community
- Website: https://flow.org
- Discord: https://discord.gg/8ezwRUK
- irc: #flowtype on Freenode
- Twitter: follow @flowtype and #flowtype to keep up with the latest Flow news.
- Stack Overflow: Ask a question with the flowtype tag
License
Flow is MIT-licensed (LICENSE). The website and documentation are licensed under the Creative Commons Attribution 4.0 license (website/LICENSE-DOCUMENTATION).