Another question for understanding. Imagine the following structure:

package_a/
  a.py
  BUILD -> python_distribution(name = "package_a")
package_b/
  b.py -> imports package_a.a
  BUILD -> python_distribution(name = "package_b")

My previous understanding was that when building wheels for

package_b

, it would detect automatically the dependency on

package_a

(via the respective file

a.py

) and I don't need to list this dependency explicityly in

python_distribution

i.e.

package_b

will just include the sources and transitive deps of the

package_a

However, some recent experiments show it is not true, so I must include

//package_a

as a

dep

of

package_b

. Is that correct? Doesn't this defeat the idea of pants taking over dep management, so that if later the actual import of

a.py

is removed, there's not dangling dependency on

package_a

remaining? Thanks! I hope I explained my issue clearly, LMK if I can refine.

can you add more information about the experiments that show the dependency is not being inferred?

〉./pants dependencies --dependencies-transitive package_b/src/b.py
(prints nothing)

〉./pants dependencies --dependencies-transitive package_b/src
package_b/src/b.py

〉./pants dependencies --dependencies-transitive package_b
package_b/src/b.py

For completeness, the zip attached and the structure is (in the same repo)

package_a
├── src
│   ├── a.py
│   └── BUILD
└── BUILD

package_b
├── src
│   ├── b.py
│   └── BUILD
└── BUILD

To be sure I understand, when you say "package_b will just include the sources and transitive deps of the package_a", do you mean that you would expect the wheel built from package_b to include the code of package_a as well as package_b?

Aha! Thanks a ton, this makes sense. So this means that Pants tries to figure out if a given source file

a.py

owned by some package producing a wheel. This makes sense. P.S. Yes (to your initial question), somehow I was thinking that even in presense of another owning wheel-creating package

package_a

, the individual sources like

a.py

shall be included directly into anyone who wants them, like

package_b

. P.P.S. Docs are amazing

Glad they were helpful!

May I ask an additional question? I could not find an answer in the docs: so in the above case, if I replace the dependant

package_b

with

pex_b

(i.e. pex depends on a file

a.py

owned by a distribution

package_a

) - is this expected that pex includes the whole of

package_a

? From what I see, when building

pex_b

I need no special

dependencies = [...]

clause in

pex_binary

. Actually it makes sense - just means that pex will contain the wheel of

package_b

inside and run normally.

A pex will contain all the code it needs, it does not have the same restriction where each source file belongs to at most one wheel

Thank you, it's clear now!