pantsbuild #development

I tried to follow down code path but it’s getting more complicated with nodes/subjects concepts, so I thought maybe you can give me some high level guidance

witty-crayon-22786

04/28/2016, 10:37 PM

@billowy-beach-68498: have you seen the visualizer?

witty-crayon-22786

04/28/2016, 10:38 PM

./pants run src/python/pants/engine/exp/examples:viz-fs --   .   ls  '3rdparty/*'

will visualize looking up files in 3rdparty

billowy-beach-68498

04/28/2016, 10:39 PM

oh I will try that. so pathglobs is subject in that test?

witty-crayon-22786

04/28/2016, 10:39 PM

yep

witty-crayon-22786

04/28/2016, 10:40 PM

you can also use the visualizer to reproduce what's happening in that test:

witty-crayon-22786

04/28/2016, 10:40 PM

./pants run src/python/pants/engine/exp/examples:viz-fs --   tests/python/pants_test/engine/exp/examples/fs_test   ls  'a/*.txt'

billowy-beach-68498

04/28/2016, 10:40 PM

I just wonder how does scheduler deal with that subject

billowy-beach-68498

04/28/2016, 10:40 PM

witty-crayon-22786

04/28/2016, 10:40 PM

@billowy-beach-68498: it looks for a task that can compute Files for a PathGlobs instance

witty-crayon-22786

04/28/2016, 10:41 PM

here https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/exp/scheduler.py#L486

witty-crayon-22786

04/28/2016, 10:42 PM

there are a few tasks that can compute Files: see https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/exp/fs.py#L393-L417

witty-crayon-22786

04/28/2016, 10:42 PM

so for each of those tasks, it will see whether it can find the appropriate inputs

witty-crayon-22786

04/28/2016, 10:44 PM

@billowy-beach-68498: did you get a chance to read https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/exp/README.md ?

billowy-beach-68498

04/28/2016, 10:45 PM

yes I did, but to be honest, a lot of concepts still confuses me

billowy-beach-68498

04/28/2016, 10:46 PM

like it didn’t explain subject, I think?

witty-crayon-22786

04/28/2016, 10:46 PM

@billowy-beach-68498: in the case of

assert_walk

, the subject is a PathGlobs initially

witty-crayon-22786

04/28/2016, 10:46 PM

"get Files for this PathGlobs"

billowy-beach-68498

04/28/2016, 10:46 PM

also select[dependencies, …] I am confused

witty-crayon-22786

04/28/2016, 10:46 PM

"get Product for this Subject"

witty-crayon-22786

04/28/2016, 10:48 PM

@billowy-beach-68498: i try to explain SelectDependencies here: https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/exp/README.md#selectors

witty-crayon-22786

04/28/2016, 10:49 PM

SelectDependencies(Files, PathGlobs)

would request

Files

for each entry in a

PathGlobs

list

witty-crayon-22786

04/28/2016, 10:50 PM

and the output would be a list of Files objects... ie

[Files(..), Files(..)]

witty-crayon-22786

04/28/2016, 10:51 PM

@billowy-beach-68498: this might be a pretty big github issue to be your first introduction to this stuff. maybe we can swap for a smaller one that would be a smoother introduction.

billowy-beach-68498

04/28/2016, 10:55 PM

well, I want to keep working on that issue since I already started on it and sooner or later I have to understand all these questions I am asking here, so I personally like the challenge here, if it’s not that urgent (like due tomorrow or sth)

witty-crayon-22786

04/28/2016, 10:56 PM

yea, not that urgent

witty-crayon-22786

04/28/2016, 10:56 PM

@billowy-beach-68498: the

fs

package is basically the most complicated set of tasks

witty-crayon-22786

04/28/2016, 10:57 PM

looking at the examples in https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/exp/examples/planners.py#L435 might make it a little easier to understand how simple tasks can be