CFN: add more validations to intrinsic FnEquals by pinzon · Pull Request #13217 · localstack/localstack

pinzon · 2025-10-02T23:16:34Z

Motivation

This PR adds a validation on the number of arguments the Fn::Equals receives. Some user are getting finding issues with the new CFn engine due to the lack of ValidationError messages.

Example:

!Equals [ !Ref Parameter]

Should be:

!Equals [!Ref Parameter, 1]

Changes

Trigger the visitation of conditions during the validation
Validate number of arguments of the Fn::Equals

Testing

AWS Validated test

github-actions · 2025-10-07T18:24:59Z

Test Results - Preflight, Unit

22 298 tests ±0 20 555 ✅ ±0 14m 58s ⏱️ - 1m 14s
1 suites ±0 1 743 💤 ±0
1 files ±0 0 ❌ ±0

Results for commit 38c6319. ± Comparison against base commit 658d6fb.

This pull request removes 1 and adds 1 tests. Note that renamed tests count towards both.

tests.unit.test_moto ‑ test_service_exception_translator_context_manager

tests.unit.aws.handlers.test_service.TestServiceExceptionSerializer ‑ test_moto_exception_is_parsed

♻️ This comment has been updated with latest results.

github-actions · 2025-10-07T18:33:44Z

Test Results (amd64) - Acceptance

7 tests ±0 5 ✅ ±0 3m 28s ⏱️ +5s
1 suites ±0 2 💤 ±0
1 files ±0 0 ❌ ±0

Results for commit 38c6319. ± Comparison against base commit 658d6fb.

♻️ This comment has been updated with latest results.

github-actions · 2025-10-07T18:34:59Z

LocalStack Community integration with Pro

2 files ± 0 2 suites ±0 36m 12s ⏱️ - 1h 23m 16s
585 tests - 4 228 471 ✅ - 4 005 114 💤 - 223 0 ❌ ±0
587 runs - 4 228 471 ✅ - 4 005 116 💤 - 223 0 ❌ ±0

Results for commit 38c6319. ± Comparison against base commit 658d6fb.

This pull request removes 4228 tests.

tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_lambda_dynamodb
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_opensearch_crud
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_search_books
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_setup
tests.aws.scenario.kinesis_firehose.test_kinesis_firehose.TestKinesisFirehoseScenario ‑ test_kinesis_firehose_s3
tests.aws.scenario.lambda_destination.test_lambda_destination_scenario.TestLambdaDestinationScenario ‑ test_destination_sns
tests.aws.scenario.lambda_destination.test_lambda_destination_scenario.TestLambdaDestinationScenario ‑ test_infra
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_prefill_dynamodb_table
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_stepfunctions_input_recipient_list[step_function_input0-SUCCEEDED]
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_stepfunctions_input_recipient_list[step_function_input1-SUCCEEDED]
…

♻️ This comment has been updated with latest results.

github-actions · 2025-10-07T18:46:10Z

Test Results (amd64) - Integration, Bootstrap

5 files ± 0 5 suites ±0 48m 51s ⏱️ - 1h 49m 36s
609 tests - 4 578 496 ✅ - 4 194 113 💤 - 384 0 ❌ ±0
615 runs - 4 578 496 ✅ - 4 194 119 💤 - 384 0 ❌ ±0

Results for commit 38c6319. ± Comparison against base commit 658d6fb.

This pull request removes 4578 tests.

tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_lambda_dynamodb
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_opensearch_crud
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_search_books
tests.aws.scenario.bookstore.test_bookstore.TestBookstoreApplication ‑ test_setup
tests.aws.scenario.kinesis_firehose.test_kinesis_firehose.TestKinesisFirehoseScenario ‑ test_kinesis_firehose_s3
tests.aws.scenario.lambda_destination.test_lambda_destination_scenario.TestLambdaDestinationScenario ‑ test_destination_sns
tests.aws.scenario.lambda_destination.test_lambda_destination_scenario.TestLambdaDestinationScenario ‑ test_infra
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_prefill_dynamodb_table
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_stepfunctions_input_recipient_list[step_function_input0-SUCCEEDED]
tests.aws.scenario.loan_broker.test_loan_broker.TestLoanBrokerScenario ‑ test_stepfunctions_input_recipient_list[step_function_input1-SUCCEEDED]
…

♻️ This comment has been updated with latest results.

github-actions · 2025-10-07T18:57:30Z

Test Results - Alternative Providers

584 tests - 783 330 ✅ - 381 26m 4s ⏱️ - 13m 52s
1 suites - 4 254 💤 - 402
1 files - 4 0 ❌ ± 0

Results for commit 38c6319. ± Comparison against base commit 658d6fb.

This pull request removes 783 tests.

tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_basic_operations_multiple_protocols[json]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_basic_operations_multiple_protocols[query]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_basic_operations_multiple_protocols[smithy-rpc-v2-cbor]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_exception_serializing_with_no_shape_in_spec[json]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_exception_serializing_with_no_shape_in_spec[query]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_exception_serializing_with_no_shape_in_spec[smithy-rpc-v2-cbor]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_multi_protocol_client_fixture[json]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_multi_protocol_client_fixture[query]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudWatchMultiProtocol ‑ test_multi_protocol_client_fixture[smithy-rpc-v2-cbor]
tests.aws.services.cloudwatch.test_cloudwatch.TestCloudwatch ‑ test_alarm_lambda_target
…

♻️ This comment has been updated with latest results.

simonrw

I think the test construction (with unused condition) is a little weird, however it's still valid behaviour that we now have parity with!

simonrw · 2025-10-10T13:58:28Z

tests/aws/services/cloudformation/test_change_set_fn_split.snapshot.json

      }
    }
+  },
+  "tests/aws/services/cloudformation/test_change_set_fn_split.py::TestValidations::test_validate_args_len": {


question: where did these snapshots come from? I guess they are left over from your split PR (#13244), can we remove them before merging?

You're right. Nice catch 👍

simonrw · 2025-10-10T14:01:40Z

tests/aws/services/cloudformation/engine/test_conditions.py

+    @skip_if_legacy_engine
+    def test_validate_equals_args_len(self, aws_client, snapshot):
+        template = {
+            "Conditions": {"ShouldDeploy": {"Fn::Equals": ["a"]}},


TIL you can have a condition that's unused!

simonrw · 2025-10-10T14:03:49Z

localstack-core/localstack/services/cloudformation/engine/v2/change_set_model_visitor.py

        # entities (parameters, mappings, conditions, etc.). Then compute the output fields; computing
        # only the output fields would only result in the deployment logic of the referenced outputs
        # being evaluated, hence enforce the visiting of all the resources first.
+        self.visit(node_template.conditions)


I guess this is only needed because in your test you have an unused condition, but in general this should not be required since resources would refer to the conditions which would cause the visiting process to visit the conditions, right?

I'm glad we have this extra parity with explicitly visiting the conditions (perhaps we should explicitly visit all nodes?) but it seems like a more contrived change than it needs to be.

I'll leave this here for now. But I have an idea to discuss later.

pinzon added this to the Playground milestone Oct 2, 2025

pinzon force-pushed the cp/cfn/v2/validations branch from fad4290 to 8f1c4ef Compare October 7, 2025 18:04

pinzon added 2 commits October 8, 2025 12:58

Fn::Split args validation

d07b2fe

cfn: add more validations to intrinsic functions

b5f6aea

pinzon force-pushed the cp/cfn/v2/validations branch from 8f1c4ef to b5f6aea Compare October 8, 2025 18:02

CFN: Add Validation to FnEquals

6d764d0

pinzon changed the title ~~Cp/cfn/v2/validations~~ cfn: add more validations to intrinsic functions Oct 8, 2025

pinzon changed the title ~~cfn: add more validations to intrinsic functions~~ CFN: add more validations to intrinsic FnEquals Oct 8, 2025

skip if v1

b0f5338

pinzon mentioned this pull request Oct 8, 2025

CFN: add validation to FnSplit #13244

Merged

remove unrelated validation

840ba70

pinzon force-pushed the cp/cfn/v2/validations branch from ffeb0eb to 840ba70 Compare October 8, 2025 21:39

pinzon marked this pull request as ready for review October 9, 2025 01:34

pinzon requested review from dominikschubert and simonrw as code owners October 9, 2025 01:34

simonrw approved these changes Oct 10, 2025

View reviewed changes

remove unrelated snapshot and validation

38c6319

pinzon merged commit 69ed784 into main Oct 10, 2025
40 checks passed

pinzon deleted the cp/cfn/v2/validations branch October 10, 2025 17:18

baermat pushed a commit that referenced this pull request Oct 13, 2025

CFN: add more validations to intrinsic FnEquals (#13217)

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LocalStack Community integration with Pro

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