External transformers

It is possible to develop your own transformers. You can use module name (if it is installed in your env) or path to file with class to run external transformers with robotidy:

robotidy --transform MyTransformers.YourCustomTransformer src
robotidy --transform C:\transformers\YourCustomTransformer2.py src

External transformers can be configured in the same way internal transformers are configured - see Configuring Transformers.

You can use the same syntax robotidy is using for developing internal transformers. The name of the file should be the same as name of the class containing your transformer. Your transformer should inherit from robot.api.parsing.ModelTransformer parent class.

from robot.api.parsing import ModelTransformer


class YourCustomTransformer(ModelTransformer):
    """
    This transformer will remove tests with
    word "deprecated" in the test case name
    """
    def visit_TestCase(self, node):
        if 'deprecated' in node.name:
            return None
        return node

Configurable params should be supplied through __init__ together with the type and default value

from robot.api.parsing import EmptyLine, ModelTransformer


class ExternalTransformer(ModelTransformer):
    """
    This transformer add `param` number of empty lines at the end of
    *** Settings *** section.
    """
    def __init__(self, param: int = 10):
        self.param = param

    def visit_SettingSection(self, node):  # noqa
        empty_line = EmptyLine.from_params()
        node.body += [empty_line] * self.param
        return node

ModelTransformer vs Transformer

Instead of using RobotFramework ModelTransformer class directly, it is possible to inherit from Robotidy Transformer class:

from robotidy.transformers import Transformer


class ExternalTransformer(Transformer):
    def __init__(self):
        super().__init__()

Transformer also inherits from ModelTransformer but provides more utility methods (and better lint support). However because of how we are dynamically loading class arguments from cli/config we need to make a call to super().__init__() even if our class don’t have any arguments to set. If you’re unsure what to use - use ModelTransformer.