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Version: 2.1 (deprecated)

Extending pre-existing targets

Adding new fields to target types.

When to add new fields?​

Adding new fields is useful when you are already using a target type, but need to store additional metadata for your plugin.

For example, if you're writing a codegen plugin to convert a protobuf_library into Java source files, you may want to add a jdk_version field to protobuf_library.

If you are instead adding support for a new language, create a new target type.

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

How to add new fields​

First, define the field. Then, register it by using OriginalTarget.register_plugin_field(CustomField), like this:

plugins/register.py
from pants.backend.codegen.protobuf.target_types import ProtobufLibrary
from pants.engine.target import BoolField


class ProtobufJdkVersion(IntField):
    """Which JDK protobuf should target."""

    alias = "jdk_version"
    default = 11


def rules():
    return [ProtobufLibrary.register_plugin_field(ProtobufJdkVersion)]

To confirm this worked, run ./pants help protobuf_library, and you should see your new field.