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

Question

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

hundreds-breakfast-49010 · Answer

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

aloof-angle-91616 · Answer

lots of stuff in `src python pants engine legacy ` let me provide some useful links

aloof-angle-91616 · Answer

so <https github com pantsbuild pants blob e873547288042aa4e6bd27bc18f2287f41eb24f3 src python pants engine legacy parser py L132> is where the magic happens

aloof-angle-91616 · Answer

as in we `exec` some python source code which is just a unicode string using the `self symbols` as an environment

aloof-angle-91616 · Answer

`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 · Answer

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 · Answer

you ll note that in that ` call ` impl we call `self parse context storage add obj `

aloof-angle-91616 · Answer

`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 · Answer

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