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Add support for operation functions
This PR adds helpers to the Python SDK to make writing operation functions easier. Operation functions use the same FunctionRunnerService RPC as composition functions, but they have different patterns for accessing required resources and returning output data. The new request.py module provides functions to get required resources (previously called "extra resources" in composition functions) and includes a helper specifically for accessing watched resources in WatchOperations. The response.py module gets new functions to set operation output and build resource requirements Signed-off-by: Nic Cope <nicc@rk0n.org>
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‎.gitignore‎

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# We don't commit our docs - instead we generate them and upload to GitHub pages.
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docs
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# AIs
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.claude/

‎crossplane/function/request.py‎

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# Copyright 2025 The Crossplane Authors.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Utilities for working with RunFunctionRequests."""
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import crossplane.function.proto.v1.run_function_pb2 as fnv1
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from crossplane.function import resource
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def get_required_resources(req: fnv1.RunFunctionRequest, name: str) -> list[dict]:
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"""Get required resources by name from the request.
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Args:
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req: The RunFunctionRequest containing required resources.
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name: The name of the required resource set to get.
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Returns:
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A list of resources as dictionaries. Empty list if not found.
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Required resources are previously called "extra resources" in composition
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functions. For operation functions, there are no observed resources, so
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all resources are "required" resources that the function requested.
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"""
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if name not in req.required_resources:
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return []
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return [
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resource.struct_to_dict(item.resource)
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for item in req.required_resources[name].items
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]
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def get_watched_resource(req: fnv1.RunFunctionRequest) -> dict | None:
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"""Get the watched resource that triggered this operation.
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Args:
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req: The RunFunctionRequest to check for a watched resource.
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Returns:
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The watched resource as a dictionary, or None if not found.
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When a WatchOperation creates an Operation, it injects the resource that
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changed using the special requirement name 'ops.crossplane.io/watched-resource'.
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This helper makes it easy to access that resource.
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"""
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watched = get_required_resources(req, "ops.crossplane.io/watched-resource")
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return watched[0] if watched else None
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def get_required_resource(req: fnv1.RunFunctionRequest, name: str) -> dict | None:
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"""Get a single required resource by name from the request.
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Args:
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req: The RunFunctionRequest containing required resources.
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name: The name of the required resource to get.
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Returns:
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The first resource as a dictionary, or None if not found.
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This is a convenience function for when you know there should be exactly
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one resource with the given requirement name.
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"""
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resources = get_required_resources(req, name)
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return resources[0] if resources else None

‎crossplane/function/response.py‎

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import datetime
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from google.protobuf import duration_pb2 as durationpb
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from google.protobuf import struct_pb2 as structpb
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import crossplane.function.proto.v1.run_function_pb2 as fnv1
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from crossplane.function import resource
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"""The default TTL for which a RunFunctionResponse may be cached."""
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DEFAULT_TTL = datetime.timedelta(minutes=1)
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message=message,
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)
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)
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def set_output(rsp: fnv1.RunFunctionResponse, output: dict | structpb.Struct) -> None:
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"""Set the output field in a RunFunctionResponse for operation functions.
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Args:
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rsp: The RunFunctionResponse to update.
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output: The output data as a dictionary or protobuf Struct.
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Operation functions can return arbitrary output data that will be written
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to the Operation's status.pipeline field. This function sets that output
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on the response.
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"""
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match output:
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case dict():
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rsp.output.CopyFrom(resource.dict_to_struct(output))
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case structpb.Struct():
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rsp.output.CopyFrom(output)
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case _:
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t = type(output)
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msg = f"Unsupported output type: {t}"
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raise TypeError(msg)
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def require_resources( # noqa: PLR0913
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rsp: fnv1.RunFunctionResponse,
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name: str,
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api_version: str,
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kind: str,
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*,
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match_name: str | None = None,
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match_labels: dict[str, str] | None = None,
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namespace: str | None = None,
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) -> None:
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"""Add a resource requirement to the response.
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Args:
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rsp: The RunFunctionResponse to update.
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name: The name to use for this requirement.
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api_version: The API version of resources to require.
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kind: The kind of resources to require.
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match_name: Match a resource by name (mutually exclusive with match_labels).
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match_labels: Match resources by labels (mutually exclusive with match_name).
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namespace: The namespace to search in (optional).
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Raises:
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ValueError: If both match_name and match_labels are provided, or neither.
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This tells Crossplane to fetch the specified resources and include them
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in the next call to the function in req.required_resources[name].
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"""
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if (match_name is None) == (match_labels is None):
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msg = "Exactly one of match_name or match_labels must be provided"
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raise ValueError(msg)
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selector = fnv1.ResourceSelector(
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api_version=api_version,
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kind=kind,
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)
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if match_name is not None:
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selector.match_name = match_name
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if match_labels is not None:
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selector.match_labels.labels.update(match_labels)
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if namespace is not None:
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selector.namespace = namespace
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rsp.requirements.resources[name].CopyFrom(selector)

‎tests/test_request.py‎

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# Copyright 2025 The Crossplane Authors.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import dataclasses
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import unittest
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import crossplane.function.proto.v1.run_function_pb2 as fnv1
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from crossplane.function import logging, request, resource
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class TestRequest(unittest.TestCase):
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def setUp(self) -> None:
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logging.configure(level=logging.Level.DISABLED)
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def test_get_required_resources(self) -> None:
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@dataclasses.dataclass
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class TestCase:
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reason: str
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req: fnv1.RunFunctionRequest
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name: str
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want: list[dict]
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cases = [
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TestCase(
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reason="Should return empty list when requirement name not found.",
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req=fnv1.RunFunctionRequest(),
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name="non-existent",
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want=[],
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),
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TestCase(
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reason="Should return resources when requirement name exists.",
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req=fnv1.RunFunctionRequest(
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required_resources={
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"test-resources": fnv1.Resources(
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items=[
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "v1",
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"kind": "Pod",
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"metadata": {"name": "test-pod"},
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}
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)
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),
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "v1",
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"kind": "Service",
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"metadata": {"name": "test-svc"},
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}
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)
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),
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]
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)
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}
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),
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name="test-resources",
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want=[
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{
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"apiVersion": "v1",
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"kind": "Pod",
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"metadata": {"name": "test-pod"},
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},
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{
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"apiVersion": "v1",
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"kind": "Service",
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"metadata": {"name": "test-svc"},
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},
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],
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),
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]
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for case in cases:
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got = request.get_required_resources(case.req, case.name)
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self.assertEqual(case.want, got, case.reason)
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def test_get_watched_resource(self) -> None:
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@dataclasses.dataclass
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class TestCase:
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reason: str
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req: fnv1.RunFunctionRequest
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want: dict | None
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cases = [
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TestCase(
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reason="Should return None when no watched resource exists.",
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req=fnv1.RunFunctionRequest(),
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want=None,
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),
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TestCase(
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reason="Should return watched resource when it exists.",
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req=fnv1.RunFunctionRequest(
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required_resources={
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"ops.crossplane.io/watched-resource": fnv1.Resources(
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items=[
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "example.org/v1",
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"kind": "App",
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"metadata": {"name": "watched-app"},
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}
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)
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)
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]
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)
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}
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),
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want={
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"apiVersion": "example.org/v1",
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"kind": "App",
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"metadata": {"name": "watched-app"},
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},
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),
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]
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for case in cases:
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got = request.get_watched_resource(case.req)
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self.assertEqual(case.want, got, case.reason)
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def test_get_required_resource(self) -> None:
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@dataclasses.dataclass
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class TestCase:
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reason: str
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req: fnv1.RunFunctionRequest
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name: str
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want: dict | None
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cases = [
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TestCase(
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reason="Should return None when requirement name not found.",
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req=fnv1.RunFunctionRequest(),
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name="non-existent",
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want=None,
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),
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TestCase(
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reason="Should return first resource when requirement name exists.",
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req=fnv1.RunFunctionRequest(
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required_resources={
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"single-resource": fnv1.Resources(
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items=[
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "v1",
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"kind": "ConfigMap",
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"metadata": {"name": "test-cm"},
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}
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)
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)
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]
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)
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}
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),
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name="single-resource",
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want={
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"apiVersion": "v1",
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"kind": "ConfigMap",
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"metadata": {"name": "test-cm"},
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},
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),
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TestCase(
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reason="Should return first resource when multiple resources exist.",
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req=fnv1.RunFunctionRequest(
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required_resources={
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"multi-resource": fnv1.Resources(
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items=[
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "v1",
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"kind": "Secret",
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"metadata": {"name": "first-secret"},
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}
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)
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),
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fnv1.Resource(
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resource=resource.dict_to_struct(
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{
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"apiVersion": "v1",
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"kind": "Secret",
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"metadata": {"name": "second-secret"},
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}
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)
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),
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]
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)
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}
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),
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name="multi-resource",
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want={
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"apiVersion": "v1",
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"kind": "Secret",
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"metadata": {"name": "first-secret"},
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},
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),
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]
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for case in cases:
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got = request.get_required_resource(case.req, case.name)
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self.assertEqual(case.want, got, case.reason)
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if __name__ == "__main__":
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unittest.main()

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