Skip to main content
Version: 2.8 (deprecated)

Creating new targets

How to add a custom target type.

When to create a new target type?

Adding new target types is most helpful when you are adding support for a new language.

If you instead want to reduce boilerplate in BUILD files, such as changing default values, use macros .

If you are already using a target type, but need to store additional metadata for your plugin, add a new field to the target type.

Step 1: Define the target type

To define a new target:

  1. Subclass
  2. Define the class property alias. This is the symbol that people use in BUILD files.
  3. Define the class property core_fields.
  4. Define the class property help. This is used by ./pants help.

For core_fields, we recommend including COMMON_TARGET_FIELDS to add the useful tags and description fields. You will also often want to add Dependencies, and either SingleSourceField or MultipleSourcesField.

from import (

class CustomField(StringField):
alias = "custom_field"
help = "A custom field."

class CustomTarget(Target):
alias = "custom_target"
core_fields = (*COMMON_TARGET_FIELDS, Dependencies, SingleSourceField, CustomField)
help = (
"A custom target to demo the Target API.\n\n"
"This docstring will be used in the output of "
"`./pants help $target_type`."
Tip: subclass SingleSourceField or MultipleSourcesField

Use SingleSourceField for source: str and MultipleSourcesField for sources: Iterable[str].

You will often want to subclass either of these fields to give custom functionality:

  • set the default
  • set expected_file_extensions, e.g. to (".json", ".txt")
  • set expected_num_files, e.g. to 1 or range(0, 5) (i.e. 0 to 4 files)
Using the fields of an existing target type

Sometimes, you may want to create a new target type that behaves similarly to one that already exists, except for some small changes.

For example, you might like how pex_binary behaves in general, but you have a Django application and keep writing entry_point="". Normally, you should write a macro to set this default value; but, here, you also want to add new Django-specific fields, so you decide to create a new target type.

Rather than subclassing the original target type, use this pattern:

from pants.backend.python.target_types import PexBinaryTarget, PexEntryPointField
from import Target
from pants.util.ordered_set import FrozenOrderedSet

class DjangoEntryPointField(PexEntryPointField):
default = ""

class DjangoManagePyTarget(Target):
alias = "django_manage_py"
core_fields = (
*(FrozenOrderedSet(PexBinaryTarget.core_fields) - {PexEntryPoint}),

In this example, we register all of the fields of PexBinaryTarget, except for the field PexEntryPoint . We instead register our custom field DjangoEntryPointField .

Step 2: Register the target type in

Now, in your, add the target type to the def target_types() entry point.

from plugins.target_types import CustomTarget

def target_types():
return [CustomTarget]

You can confirm this works by running ./pants help custom_target.