i learned how we actually do BUILD file parsing on the fligh Pants #development

i learned how we actually do BUILD file parsing on...

aloof-angle-91616

11/27/2019, 8:38 PM

i learned how we actually do BUILD file parsing on the flight i just got off of. not planning to change anything about that right now, but can answer questions if anyone has them in the future!

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hundreds-breakfast-49010

11/27/2019, 8:45 PM

where's a good place to look in the code for this?

aloof-angle-91616

11/27/2019, 8:51 PM

lots of stuff in

src/python/pants/engine/legacy/

, let me provide some useful links

aloof-angle-91616

11/27/2019, 8:52 PM

so https://github.com/pantsbuild/pants/blob/e873547288042aa4e6bd27bc18f2287f41eb24f3/src/python/pants/engine/legacy/parser.py#L132 is where the magic happens

aloof-angle-91616

11/27/2019, 8:52 PM

as in, we

exec

some python source code (which is just a unicode string), using the

self._symbols

as an environment

aloof-angle-91616

11/27/2019, 8:53 PM

self._symbols

is a dict mapping

str -> Registrar

, as per https://github.com/pantsbuild/pants/blob/e873547288042aa4e6bd27bc18f2287f41eb24f3/src/python/pants/engine/legacy/parser.py#L57

aloof-angle-91616

11/27/2019, 8:54 PM

the

__call__

method is invoked when the symbol in

str

is encountered: https://github.com/pantsbuild/pants/blob/e873547288042aa4e6bd27bc18f2287f41eb24f3/src/python/pants/engine/legacy/parser.py#L68-L85

aloof-angle-91616

11/27/2019, 8:56 PM

you'll note that in that

__call__

impl, we call

self._parse_context._storage.add(obj)

aloof-angle-91616

11/27/2019, 8:56 PM

ParseContext

and

Storage

are both defined in https://github.com/pantsbuild/pants/blob/e873547288042aa4e6bd27bc18f2287f41eb24f3/src/python/pants/base/parse_context.py#L8

aloof-angle-91616

11/27/2019, 8:57 PM

and that's what manages the state that parsing a BUILD file affects

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