Given https://github.com/pantsbuild/example-python/, here are all the targets:

$ pants list ::                     
//:_python-default_lockfile
//:reqs
//:reqs#ansicolors
//:reqs#pytest
//:reqs#setuptools
//:reqs#types-setuptools
//python-default.lock:_python-default_lockfile
//requirements.txt:reqs
helloworld:lib
helloworld:pex_binary
helloworld/__init__.py:lib
helloworld/main.py:lib
helloworld/greet:lib
helloworld/greet:tests
helloworld/greet:translations
helloworld/greet/__init__.py:lib
helloworld/greet/greeting.py:lib
helloworld/greet/greeting_test.py:tests
helloworld/translator:dist
helloworld/translator:lib
helloworld/translator:tests
helloworld/translator/__init__.py:lib
helloworld/translator/translator.py:lib
helloworld/translator/translator_test.py:tests

say I want to exclude

helloworld/greet:lib

as if it doesn't exist at all:

-python_sources(
-    name="lib",
-    dependencies=[":translations"],
-)

now if I run the

test

goal I do get an error since the

python_sources

do not exist any longer:

$ pants test helloworld/greet
13:22:30.32 [ERROR] Completed: Run Pytest - helloworld/greet/greeting_test.py:tests - failed (exit code 2).
...
Traceback:
/usr/lib64/python3.9/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
helloworld/greet/greeting_test.py:4: in <module>
    from helloworld.greet.greeting import Greeter
E   ModuleNotFoundError: No module named 'helloworld.greet.greeting'
- generated xml file: /tmp/pants-sandbox-6oBsCG/helloworld.greet.greeting_test.py.tests.xml -
=========================== short test summary info ============================
ERROR helloworld/greet/greeting_test.py

✕ helloworld/greet/greeting_test.py:tests failed in 0.29s.

Is there a way to exclude a build target like this without commenting it out in the BUILD file? 😄 Using

--tags

would work when selecting targets, same with `--filter`; here I want to exclude it from the dependency graph as if it didn't exist at all.

the closest I was able to get is to dynamically extend the Pants ignored list:

pants --pants-ignore="+['helloworld/greet/greeting.py']" test helloworld/greet

but this would only work for paths to files whereas I am interested in accessing the build targets, e.g.

pants --exclude="+['helloworld/greet:lib']" test helloworld/greet

Also

--pants-ignore="+['helloworld/greet/greeting.py']"

won't work if there's a

python_source

build target with the exact path:

python_source(name="foo", source="helloworld/greet/greeting.py")

as Pants correctly complains about

InvalidFieldException

- a build target with the source must point to an existing file on disk

that is, you could have an alias for adding or removing this entry from the list of patterns..

I'll make sure this is reflected in the documentation!!

I'll wait for a bit and then open an issue I think proposing to add the exclude semantics - essentially removing a node from the dependency graph, dynamically. Another huge use case is dependency graph explorations I've been busy with for the past year. Say you want to eradicate dependency on a library in your application. How difficult would it be? So you go and comment the import line in the application program, but then it's picked as a transitive dependency. You keep commenting out it in other places until you are done. But it's tedious. It would be helpful to say - imagine this library doesn't exist, how does my graph look better? I.e. do I still have lots of tests picked up after arbitrary change or not?