(aws-cloudwatch): Missing ids when creating math expressions

There’s no way to assign an ID to a metric in CDK at this point. If you’re creating multiple math expressions within a single dashboard widget, the IDs for the math expressions are missing, and you’ll see that they have the same IDs in the CloudWatch Dashboard, and the metrics in the dashboard widget will be messed up.

Reproduction Steps

new cloudWatch.GraphWidget({
    left: [
        new MathExpression(...),
        new MathExpression(...),
        new MathExpression(...)
    ]
});

The generated CloudFormation file doesn’t contain ID for MathExpression (see example below). After deployed, in the CloudWatch, we’ll see that all the math expressions are assigned with the same ID, and the dashboard widget shows incorrect metrics

{ "label": "percentage", "expression": "m1 / m2", "region": "us-east-1" }

What did you expect to happen?

• There should be a way to auto or manually set the ID for MathExpression
• The above example should finally contain an id, something like

{ "label": "percentage", "expression": "m1 / m2", "region": "us-east-1", id: "e1" }

What actually happened?

The generated Math Expression widget doesn’t have an id

{ "label": "percentage", "expression": "m1 / m2", "region": "us-east-1" }

Environment

• CDK CLI Version : any
• Framework Version: 1.95
• Node.js Version: any
• OS : any
• Language (Version): TypeScript (but I think this issue is in all the languages)

Other

---

This is 🐛 Bug Report

[adam-kiss-sg]

If any1 else is still facing this issue: I managed to hack around it in python, something similar could work in other languages as well:

helper class:

class MyMetric(aws_cloudwatch.Metric):
    def __init__(self, *args, **kwargs):
        super(MyMetric, self).__init__(*args, **kwargs)
    
    def addProperties(self, props):
        self.props = props
        return self
    
    def to_metric_config(self) -> aws_cloudwatch.MetricConfig:
        result = super(MyMetric, self).to_metric_config()
        if not hasattr(self, "props"):
            return result
        
        if "rendering_properties" in result._values:
            result._values["rendering_properties"].update(self.props)
        else:
            result._values["rendering_properties"] = self.props
        return result

Usage: Replace: aws_cloudwatch.Metric(namespace="AWS/EC2", metric_name="NetworkIn") with: MyMetric(namespace="AWS/EC2", metric_name="NetworkIn").addProperties({"id": "yourid", "visible": false})

[github-actions[bot]]

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