(cfnspec): should be able to handle types changing from Json to type

[corymhall]

Overview

Sometimes a property type in the cfnspec is set to Json which means that it accepts any JSON value. If a service team ever adds actual types for this property it is not a breaking change on their side, but it does lead to breaking changes for us. Our current workaround is to add a patch which keeps the value as Json which is not ideal.

Issue list

Type Change
List of Properties that have changed from Json to a type

• AWS::Config::RemediationConfiguration.Parameters
  • Better types currently exist ([config] Python - generated template is invalid due to lowercase keys in the schema #8996)
• AWS::ImageBuilder::DistributionConfiguration.Distribution
• AWS::Serverless::Function.IAMPolicyDocument
• AWS::Serverless::StateMachine.IAMPolicyDocument
• AWS::Timestream::Table.MagneticStoreWriteProperties
• AWS::Timestream::Table.RetentionProperties

[madeline-k]

A solution we are working on (thanks to @rix0rrr for proposing this):

• As a postprocessing step after importing a new spec, any time we encounter a property { MyProp: { PrimitiveType: Json } }, we automatically write a patch file that adds a marker field into the property, like { MyProp: { WasOnceJson: true } } .
• In cfn2ts, for every property MyProp we encounter we look at WasOnceJson.
  • If it doesn't exist OR MyProp.PrimitiveType = 'Json', we proceed as normal.
  • If it does exist, then we emit two properties:

/**
 * MyProp (as untyped json data). The object you provide for this property will end up in your cloudformation template exactly as specified, without any capitalization alteration.
 *
 * @deprecated Use `myPropTyped` instead.
 * @default - Specify {at most|exactly} one of `myProp` and `myPropTyped`
 */
readonly myProp?: any;

/**
 * MyProp
 *
 * @default - Specify {at most|exactly} one of `myProp` and `myPropTyped`
 */
readonly myPropTyped?: MyPropType;

"At most" vs "exactly" depends on whether the original property was optional or required.

Once we have this in place, we can add the WasOnceJson field as necessary, and get rid of this patch: 4fbc182#diff-08b4822e59cb5286d16984c086cf2fe15085a336fa7a37157d923b1f408f5647

[Wurstnase]

Looks like, that the new type will generate an additional dataclass. Before the patch it is PascalCase. After this patch it becomes camelCase. Would it a big problem to make the properties PascalCase again so it would be possible to use the generated dataclasses?

In that case we could benefit with typing and autocompletion.

[peterwoodworth]

We've received a number of reports since we patched the breaking changes found in spec 101, including

#23570
#23679
#23709
#24754
#25558
#25774
#25990

[Nabeelperson]

This issue also effects: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-backup-backupselection-conditionparameter.html

I use Java CDK:

            CfnBackupSelection.Builder.create(this, id + "TagSelector")
                .backupPlanId(backupPlan.getAttrBackupPlanId())
                .backupSelection(
                    BackupSelectionResourceTypeProperty.builder()
                        .selectionName("Selector")
                        .iamRoleArn(role.getRoleArn())
                        .resources(List.of("*"))
                        .conditions(
                            Map.of(
                                "StringEquals",
                                List.of(
                                    ConditionParameterProperty.builder()
                                        .conditionKey("aws:ResourceTag/TagKey")
                                        .conditionValue("TagValue")
                                        .build()
                                )
                            )
                        )
                        .build()
                )
                .build();

Results in camelCase yaml output.