I had to add boilerplate code to a

BUILD

file for all

python_library

and

python_tests

targets. I am not considering a manual approach which would only work for a toy project. So we go for a programmatic update of the

BUILD

files. One path to take was to use an AST / CST (abstract or concrete syntax tree) based approach (since

BUILD

files are valid Python files) and then just add extra arguments to a function call. This is fairly easy given the low complexity of the

BUILD

files in my case. A few libraries to consider are: • https://github.com/python-rope/rope • https://github.com/PyCQA/redbaron • https://github.com/berkerpeksag/astor • https://github.com/Instagram/LibCST However, this may mean some work and also not everyone wants to get into the AST business 😄 Another approach was to use an OOTB tool to edit

BUILD

files which I did. Because

BUILD

files in Pants share semantics with the

BUILD

files used in Bazel, I shamelessly used buildozer (part of Bazel build tools) to update my

BUILD

files. Keep in mind it will reformat the

BUILD

file with the Bazel style which may be not what you want.

$ buildozer 'set skip_yapf True' 'set skip_mypy True' 'set skip_flake8 True' ///...:%python_tests
$ buildozer 'set skip_yapf True' 'set skip_mypy True' 'set skip_flake8 True' ///...:%python_library

Running these have modified all libraries and tests targets to have those arguments. E.g.

python_library(sources=["*/**/*.py", "!tests/"])

was turned into

python_library(
    skip_flake8 = True,
    skip_mypy = True,
    skip_yapf = True,
    sources = [
        "*/**/*.py",
        "!tests/",
    ],
)

However, I run Python formatter on the

BUILD

files anyway afterwards, so that wasn’t a problem for me:

python_library(
    skip_flake8=True,
    skip_mypy=True,
    skip_yapf=True,
    sources=[
        "*/**/*.py",
        "!tests/",
    ],
)

There are easy ways to have fine-grained control over what targets you’d like to run the editing command on, but you may need to consult the Bazel docs as they may differ from the ones used in Pants, e.g. editing only a single project files:

$ buildozer 'set skip_yapf False' 'set skip_mypy False' projectdir/subdir:%python_library

There may be plans to have some functionality similar to what

buildozer

provides as core of Pants, but until then it may be a sensible approach for some of us. I think it may be worth experimenting with.