[devy]

Hi,

I have 2 questions:

1. The installation doc specified `watchman` as a dependency. Why is that used? without watchman, would pysa not work?

2. Also, why can the pysa become a separate stand alone tool instead of living in the pyre Github repo?

[sinancepel]

1. Pysa should work without watchman - it shares some code and infrastructure with Pyre, but doesn't need Watchman to complete its analysis.

2. Hopefully the answer to (1) helps here. Pysa shares some code with Pyre, including the parallelization infrastructure - the same infrastructure that makes Pyre fast interactively makes Pysa fast on large codebases. Living on the Pyre GitHub repo allows Pysa to use the parallelization infra, in addition to the type checking APIs of Pyre as necessary.

See also our original post introducing Pyre - our goal from the outset was to build a platform for deeper static analyses: https://www.facebook.com/notes/protect-the-graph/pyre-fast-t...