cloudwatch: min property @default 0 should be Auto instead

[iankhou]

Describe the issue

The @default here is incorrect.

It should be Auto. The behavior is different. See cdklabs/construct-hub#1775 for an example.

Links

In-code documentation.

aws-cdk/packages/aws-cdk-lib/aws-cloudwatch/lib/graph.ts

Line 62 in ec18b83

* @default 0

[pahud]

Hi @iankhou,

Thank you for reporting this issue. After investigation, this is actually both a documentation AND implementation problem, not just a documentation fix.

The Issues:

1. Documentation: The @default 0 annotation in YAxisProps is misleading

2. Implementation: The GaugeWidget explicitly forces min: 0, max: 100 when undefined, overriding CloudWatch's auto-scaling:

// Current problematic code in GaugeWidget
const leftYAxis = {
 ...this.props.leftYAxis,
 min: this.props.leftYAxis?.min ?? 0,    // Forces 0!
 max: this.props.leftYAxis?.max ?? 100,  // Forces 100!
};

Widget Inconsistency:

• GraphWidget & AlarmWidget: Allow auto-scaling (correct behavior)
• GaugeWidget: Forces fixed ranges (incorrect behavior)

Proposed Fix:

1. Update documentation to reflect auto-scaling as default
2. Modify GaugeWidget to match GraphWidget behavior:

const leftYAxis = this.props.leftYAxis; // Let CloudWatch auto-scale

3. Update tests that expect hardcoded defaults

This would be a breaking change for GaugeWidget users who rely on the current 0-100 default range, so it needs careful consideration for the migration path.