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CFn: correctly skip conditionally disabled resources #13238

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simonrw merged 2 commits into from
Oct 8, 2025
Merged

CFn: correctly skip conditionally disabled resources #13238

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5a45aa0
Add test for conditionals
simonrw Oct 7, 2025
ebf3c17
Skip resources conditionally evaluating to False
simonrw Oct 7, 2025
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23 changes: 23 additions & 0 deletions localstack-core/localstack/services/cloudformation/engine/v2/change_set_model_preproc.py
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@pinzon pinzon Oct 8, 2025

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Praise: Glad the new engine is easily modifiable.

Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,7 @@
NodeProperties,
NodeProperty,
NodeResource,
NodeResources,
NodeTemplate,
Nothing,
NothingType,
Expand Down Expand Up @@ -1170,6 +1171,20 @@ def _resolve_resource_condition_reference(self, reference: TerminalValue) -> Pre
after = after_delta.after
return PreprocEntityDelta(before=before, after=after)

def visit_node_resources(self, node_resources: NodeResources):
"""
Skip resources where they conditionally evaluate to False
"""
for node_resource in node_resources.resources:
if not is_nothing(node_resource.condition_reference):
condition_delta = self._resolve_resource_condition_reference(
node_resource.condition_reference
)
condition_after = condition_delta.after
if condition_after is False:
continue
self.visit(node_resource)

def visit_node_resource(
self, node_resource: NodeResource
) -> PreprocEntityDelta[PreprocResource, PreprocResource]:
Expand Down Expand Up @@ -1280,6 +1295,14 @@ def visit_node_outputs(
before: list[PreprocOutput] = []
after: list[PreprocOutput] = []
for node_output in node_outputs.outputs:
if not is_nothing(node_output.condition_reference):
condition_delta = self._resolve_resource_condition_reference(
node_output.condition_reference
)
condition_after = condition_delta.after
if condition_after is False:
continue

output_delta: PreprocEntityDelta[PreprocOutput, PreprocOutput] = self.visit(node_output)
output_before = output_delta.before
output_after = output_delta.after
Expand Down
37 changes: 36 additions & 1 deletion tests/aws/services/cloudformation/engine/test_conditions.py
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@pinzon pinzon Oct 8, 2025

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Nit: Consider adding a validation test about a situation where an output references a conditionally skip resource.

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@simonrw simonrw Oct 8, 2025 •
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Good idea, thanks! I'll tackle this in a follow up

Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
import os.path

import pytest
from localstack_snapshot.snapshots.transformer import SortingTransformer
from tests.aws.services.cloudformation.conftest import skip_if_legacy_engine

from localstack.services.cloudformation.v2.utils import is_v2_engine
Expand Down Expand Up @@ -153,7 +154,7 @@ def test_dependent_get_att(self, aws_client, snapshot):
snapshot.match("dependent_ref_exc", e.value.response)

@markers.aws.validated
@pytest.mark.skipif(condition=not is_aws_cloud(), reason="not supported yet")
@skip_if_legacy_engine()
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@pinzon pinzon Oct 8, 2025

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🥳

def test_dependent_ref_intrinsic_fn_condition(self, aws_client, deploy_cfn_template):
"""
Checks behavior of un-refable resources
Expand Down Expand Up @@ -515,3 +516,37 @@ def test_update_conditions(self, deploy_cfn_template, aws_client):
assert aws_client.s3.head_bucket(Bucket=bucket_1)
with pytest.raises(aws_client.s3.exceptions.ClientError):
aws_client.s3.head_bucket(Bucket=bucket_2)

@markers.aws.validated
@pytest.mark.parametrize("should_deploy", ["yes", "no"])
@skip_if_legacy_engine()
def test_references_to_disabled_resources(
self, deploy_cfn_template, aws_client, should_deploy, snapshot
):
snapshot.add_transformer(
SortingTransformer("StackResources", lambda e: e["LogicalResourceId"])
)
snapshot.add_transformer(SortingTransformer("Parameters", lambda e: e["ParameterKey"]))
snapshot.add_transformer(snapshot.transform.key_value("PhysicalResourceId"))
snapshot.add_transformer(snapshot.transform.cloudformation_api())

parameter_value = short_uid()
snapshot.add_transformer(snapshot.transform.regex(parameter_value, "<parameter-value>"))

stack = deploy_cfn_template(
template_path=os.path.join(
os.path.dirname(__file__), "../../../templates/references_to_conditions.yml"
),
parameters={
"Toggle": should_deploy,
"ParameterValue": parameter_value,
},
)

describe_stack_res = aws_client.cloudformation.describe_stacks(StackName=stack.stack_id)
snapshot.match("stack-description", describe_stack_res)

describe_resources = aws_client.cloudformation.describe_stack_resources(
StackName=stack.stack_id
)
snapshot.match("resources-description", describe_resources)
158 changes: 158 additions & 0 deletions tests/aws/services/cloudformation/engine/test_conditions.snapshot.json
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Original file line number Diff line number Diff line change
Expand Up @@ -775,5 +775,163 @@
}
}
}
},
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_references_to_disabled_resources[yes]": {
"recorded-date": "07-10-2025, 21:21:23",
"recorded-content": {
"stack-description": {
"Stacks": [
{
"Capabilities": [
"CAPABILITY_AUTO_EXPAND",
"CAPABILITY_IAM",
"CAPABILITY_NAMED_IAM"
],
"ChangeSetId": "arn:<partition>:cloudformation:<region>:111111111111:changeSet/<resource:1>",
"CreationTime": "datetime",
"DisableRollback": false,
"DriftInformation": {
"StackDriftStatus": "NOT_CHECKED"
},
"EnableTerminationProtection": false,
"LastUpdatedTime": "datetime",
"NotificationARNs": [],
"Outputs": [
{
"OutputKey": "ConditionalParameterValue",
"OutputValue": "<parameter-value>"
}
],
"Parameters": [
{
"ParameterKey": "ParameterValue",
"ParameterValue": "<parameter-value>"
},
{
"ParameterKey": "Toggle",
"ParameterValue": "yes"
}
],
"RollbackConfiguration": {},
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"StackStatus": "CREATE_COMPLETE",
"Tags": []
}
],
"ResponseMetadata": {
"HTTPHeaders": {},
"HTTPStatusCode": 200
}
},
"resources-description": {
"StackResources": [
{
"DriftInformation": {
"StackResourceDriftStatus": "NOT_CHECKED"
},
"LogicalResourceId": "AnotherResource",
"PhysicalResourceId": "<physical-resource-id:1>",
"ResourceStatus": "CREATE_COMPLETE",
"ResourceType": "AWS::SSM::Parameter",
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"Timestamp": "timestamp"
},
{
"DriftInformation": {
"StackResourceDriftStatus": "NOT_CHECKED"
},
"LogicalResourceId": "BaseParameter",
"PhysicalResourceId": "<physical-resource-id:2>",
"ResourceStatus": "CREATE_COMPLETE",
"ResourceType": "AWS::SSM::Parameter",
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"Timestamp": "timestamp"
},
{
"DriftInformation": {
"StackResourceDriftStatus": "NOT_CHECKED"
},
"LogicalResourceId": "ConditionalParameter",
"PhysicalResourceId": "<physical-resource-id:3>",
"ResourceStatus": "CREATE_COMPLETE",
"ResourceType": "AWS::SSM::Parameter",
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"Timestamp": "timestamp"
}
],
"ResponseMetadata": {
"HTTPHeaders": {},
"HTTPStatusCode": 200
}
}
}
},
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_references_to_disabled_resources[no]": {
"recorded-date": "07-10-2025, 21:21:37",
"recorded-content": {
"stack-description": {
"Stacks": [
{
"Capabilities": [
"CAPABILITY_AUTO_EXPAND",
"CAPABILITY_IAM",
"CAPABILITY_NAMED_IAM"
],
"ChangeSetId": "arn:<partition>:cloudformation:<region>:111111111111:changeSet/<resource:1>",
"CreationTime": "datetime",
"DisableRollback": false,
"DriftInformation": {
"StackDriftStatus": "NOT_CHECKED"
},
"EnableTerminationProtection": false,
"LastUpdatedTime": "datetime",
"NotificationARNs": [],
"Parameters": [
{
"ParameterKey": "ParameterValue",
"ParameterValue": "<parameter-value>"
},
{
"ParameterKey": "Toggle",
"ParameterValue": "no"
}
],
"RollbackConfiguration": {},
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"StackStatus": "CREATE_COMPLETE",
"Tags": []
}
],
"ResponseMetadata": {
"HTTPHeaders": {},
"HTTPStatusCode": 200
}
},
"resources-description": {
"StackResources": [
{
"DriftInformation": {
"StackResourceDriftStatus": "NOT_CHECKED"
},
"LogicalResourceId": "BaseParameter",
"PhysicalResourceId": "<physical-resource-id:1>",
"ResourceStatus": "CREATE_COMPLETE",
"ResourceType": "AWS::SSM::Parameter",
"StackId": "arn:<partition>:cloudformation:<region>:111111111111:stack/<stack-name:1>/<resource:2>",
"StackName": "<stack-name:1>",
"Timestamp": "timestamp"
}
],
"ResponseMetadata": {
"HTTPHeaders": {},
"HTTPStatusCode": 200
}
}
}
}
}
18 changes: 18 additions & 0 deletions tests/aws/services/cloudformation/engine/test_conditions.validation.json
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,24 @@
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_output_reference_to_skipped_resource": {
"last_validated_date": "2023-06-26T22:43:18+00:00"
},
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_references_to_disabled_resources[no]": {
"last_validated_date": "2025-10-07T21:21:41+00:00",
"durations_in_seconds": {
"setup": 0.0,
"call": 7.01,
"teardown": 4.39,
"total": 11.4
}
},
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_references_to_disabled_resources[yes]": {
"last_validated_date": "2025-10-07T21:21:30+00:00",
"durations_in_seconds": {
"setup": 0.89,
"call": 10.41,
"teardown": 6.43,
"total": 17.73
}
},
"tests/aws/services/cloudformation/engine/test_conditions.py::TestCloudFormationConditions::test_update_conditions": {
"last_validated_date": "2024-06-18T19:43:43+00:00"
}
Expand Down
39 changes: 39 additions & 0 deletions tests/aws/templates/references_to_conditions.yml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@
Parameters:
Toggle:
Type: String

ParameterValue:
Type: String

Conditions:
ShouldDeploy:
Fn::Equals:
- !Ref Toggle
- "yes"

Resources:
BaseParameter:
# We need a single resource to deploy
Type: AWS::SSM::Parameter
Properties:
Type: String
Value: !Ref ParameterValue

ConditionalParameter:
Type: AWS::SSM::Parameter
Condition: ShouldDeploy
Properties:
Type: String
Value: !Ref ParameterValue

AnotherResource:
Type: AWS::SSM::Parameter
Condition: ShouldDeploy
Properties:
Type: String
Value: !GetAtt ConditionalParameter.Value

Outputs:
ConditionalParameterValue:
Condition: ShouldDeploy
Value: !GetAtt ConditionalParameter.Value
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