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Create initial BUILD files

Many Pants operations require extra metadata in the form of targets, which are defined in BUILD files.

You can generate these BUILD files by running ./pants tailor:

❯ ./pants tailor
Created scripts/BUILD:
  - Add shell_sources target scripts
Created src/py/project/BUILD:
  - Add python_sources target project
  - Add python_tests target tests
Created src/go/BUILD:
  - Add go_mod target mod

Often, this will be all you need for Pants to work, thanks to sensible defaults and inference, like inferring your dependencies. Sometimes, though, you may need to or want to change certain fields, like setting a longer timeout on a test.

You may also need to add some targets that Pants cannot generate, like resources and files targets.

We recommend running ./pants tailor --check in your continuous integration so that you don't forget to add any targets and BUILD files.

❯ ./pants tailor --check
Would create scripts/BUILD:
  - Add shell_sources target scripts

To fix `tailor` failures, run `./pants tailor`.

To ignore false positives, set [tailor].ignore_paths and [tailor].ignore_adding_targets. See tailor for more detail.

[tailor]
ignore_paths = ["src/py/ignore_me/**"]
ignore_adding_targets = ["src/py/project:tgt"]

Formatting BUILD files with Black or Yapf

./pants run update-build-files will format your BUILD files, using the Black Python formatter by default. The goal will also fix any safe Pants deprecations like renaming target types.

❯ ./pants update-build-files
Updated scripts/BUILD:
  - Format with Black
  - Rename `python_library` to `python_sources`

Like tailor, we recommend running ./pants update-build-files --check in your continuous integration.

❯ ./pants update-build-files --check
Would update scripts/BUILD:
  - Format with Black
  - Rename `python_library` to `python_sources`

To fix `update-build-files` failures, run `./pants update-build-files`.

You can instead use Yapf by setting [update-build-files].formatter = "yapf" in pants.toml.