region-info: Fact.regions behavior does not match description.

[chamsco-aws]

Describe the bug

In fact.ts

aws-cdk/packages/aws-cdk-lib/region-info/lib/fact.ts

Lines 7 to 14 in ab52bb5

	/**
	* @returns the list of names of AWS regions for which there is at least one registered fact. This
	* may not be an exhaustive list of all available AWS regions.
	*/
	public static get regions(): string[] {
	// Return by copy to ensure no modifications can be made to the undelying constant.
	return Array.from(AWS_REGIONS);
	}

the description of regions it states it returns any region that has at least one fact registered. This is untrue, it is only listing from the fixed list defined in AWS_REGIONS from aws-entities.ts.

Either the description needs to be updated, or the logic needs to pull the list of regions from this.database instead of the AWS_REGIONS export.

Expected Behavior

1. Call Fact.regions and save the array as call1
2. Register a new fact with a region that has yet to be added to the list in AWS_REGIONS
3. Call Fact.regions as call2
4. The call2 array would include the name of my newly added region and the call1 array would not.

Current Behavior

1. Call Fact.regions and save the array as call1
2. Register a new fact with a region that has yet to be added to the list in AWS_REGIONS
3. Call Fact.regions as call2
4. The call2 array is identical to the call1 array.

Reproduction Steps

  it('can find new region in `Fact.region`', () => {
    Fact.register({
      region: 'us-unreleased-1',
      name: FactName.PARTITION,
      value: 'aws',
    });
    expect(Fact.regions.includes('us-unreleased-1')).toBeTruthy();
  })

Possible Solution

Switch the code from Array.from(AWS_REGIONS) to Array.from(Object.keys(this.database)) or update the documentation to say it is a fixed list based on AWS_REGIONS in aws-entities.ts

Additional Information/Context

No response

CDK CLI Version

2.95.0 (build cfa7e88)

Framework Version

No response

Node.js Version

v18.17.1

OS

OSX 13.5.2 (22G91)

Language

Typescript

Language Version

TypeScript (4.3.0)

Other information

You can reach out to me on the Amazon internal slack as @chamsco

[peterwoodworth]

Thanks for the report, makes sense!

I'm not personally familiar with why you would want to use this feature (returning regions from Fact), so I'm not sure if we should just update the documentation or adjust the functionality to match the documentation. I would think it would make sense to adjust the functionality, but there could be something I'm missing. Either way, it should be simple to address

[github-actions]

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