cloudwatch: expression warning that when e is present in the expression

[tnsardesai]

Describe the bug

CDK is displaying a warning thinking e a metric. When using the math expression 'serverError / (success + authError + clientError + serverError + 1e-36)' (to avoid division by zero we are adding 0.000000000000000000000000000000000001)

Expected Behavior

No warning

Current Behavior

[Warning at /IotStack/IoT-Connect-MQTT-ServerError1] Math expression 'serverError / (success + authError + clientError + serverError + 1e-36)' references unknown identifiers: e. Please add them to the 'usingMetrics' map. [ack: CloudWatch:Math:UnknownIdentifier]

Reproduction Steps

Simple error with no metric that always returns 0

const VERY_SMALL_NUMBER = 0.000000000000000000000000000000000001;

const errorRateMetric = new MathExpression({
  label: `Dummy error`,
  expression: `0 / 0 + ${VERY_SMALL_NUMBER})`,
  usingMetrics: {},
  period: Duration.minutes(1),
});

outputs [Warning at /IotStack-production/IoT-PublishOut-MQTT-AuthError4] Math expression '0 / 0 + 1e-36)' references unknown identifiers: e. Please add them to the 'usingMetrics' map. [ack: CloudWatch:Math:UnknownIdentifier]

Possible Solution

In https://github.com/ParkerVR/aws-cdk/blob/5daa6480fa2ebd8bfb2407d80b8df40c367ef8fd/packages/%40aws-cdk/aws-cloudwatch/lib/metric.ts#L749-L754 if identifier is e then it should be considered valid.

This function is used https://github.com/ParkerVR/aws-cdk/blob/5daa6480fa2ebd8bfb2407d80b8df40c367ef8fd/packages/%40aws-cdk/aws-cloudwatch/lib/metric.ts#L610 to give the warning

Additional Information/Context

No response

CDK CLI Version

2.105.0 (build 04cb52d)

Framework Version

No response

Node.js Version

v18.18.0

OS

macOS

Language

TypeScript

Language Version

No response

Other information

No response

[pahud]

This makes sense to me. Are you able to provide a minimal reproducible cdk app that we can reproduce and see the error messages?

[github-actions]

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