aws-pipes-alpha: InputTransformation in Pipe should automatically add expression delimiters

[garysassano]

Describe the bug

When using the AWS Pipes L2 construct, there's an inconsistency in how JSON paths are handled between queryStringParameters and inputTransformation.

For queryStringParameters, JSON paths work directly:

queryStringParameters: {
  key: "$.dynamodb.Keys.Location.S",
  ttl_seconds: "$.dynamodb.NewImage.TTL.N"
}

However, for inputTransformation, we need to manually add expression delimiters (<>) around JSON paths:

inputTransformation: InputTransformation.fromObject({
  Location: "<$.dynamodb.Keys.Location.S>",
  MaxTemp: "<$.dynamodb.NewImage.MaxTemp.N>",
  MinTemp: "<$.dynamodb.NewImage.MinTemp.N>",
  ChancesOfPrecipitation: "<$.dynamodb.NewImage.ChancesOfPrecipitation.N>"
})

This creates an inconsistent developer experience and increases the chance of errors if developers forget to add the delimiters.

Suggested Solution

The L2 construct should automatically add the required expression delimiters (<>) around JSON paths in inputTransformation objects, similar to how queryStringParameters handles paths directly.

Example of desired API:

inputTransformation: InputTransformation.fromObject({
  Location: "$.dynamodb.Keys.Location.S",
  MaxTemp: "$.dynamodb.NewImage.MaxTemp.N",
  MinTemp: "$.dynamodb.NewImage.MinTemp.N",
  ChancesOfPrecipitation: "$.dynamodb.NewImage.ChancesOfPrecipitation.N"
})

The L2 construct could detect JSON paths (starting with $.) and automatically wrap them in expression delimiters, improving developer experience and preventing errors from forgotten delimiters.

Regression Issue

• Select this option if this issue appears to be a regression.

Last Known Working CDK Version

No response

Expected Behavior

See above.

Current Behavior

See above.

Reproduction Steps

See above.

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

2.172.0

Framework Version

No response

Node.js Version

22.11.0

OS

Ubuntu 24.04

Language

TypeScript

Language Version

No response

Other information

No response

[pahud]

Yes this seems to be inconsistent developer experience. Not sure if this is intentional. We'll bring this up to the team for inputs.