Issue with CloudWatch MetricDatum Unit types

[EHadoux]

Describe the bug

When using PutMetricDataCommand the field MetricData expects a MetricDatum[]. The Unit field of MetricDatum has in theory the type StandardUnit | string. It looks like it gets coerced to string only because StardardUnit is a union of string. We lose the autocompletion of the possible values for the unit. See

aws-sdk-js-v3/clients/client-cloudwatch/src/models/models_0.ts

Line 3502 in e0025cd

Unit?: StandardUnit | string;

Your environment

SDK version number

@aws-sdk/client-cloudwatch@3.35.0

Is the issue in the browser/Node.js/ReactNative?

Node.js

Details of the browser/Node.js/ReactNative version

v16.9.1

Steps to reproduce

import { PutMetricDataCommand } from '@aws-sdk/client-cloudwatch';

const cmd = new PutMetricDataCommand({
  MetricData: [{
    Unit: 'Count' // of type string so no autocompletion
  }]
});

Observed behavior

The Unit field is of type string, preventing autocompletion.

Expected behavior

The Unit field should be of type StandardUnit to allow for autocompletion.

Screenshots

Additional context

Using Typescript v4.4.3

[vudh1]

Hi @EHadoux, I am not able to reproduce this with the code you gave above. Can you send a reproducible code/log so we can investigate more?

[EHadoux]

Hi @vudh1, by not being able to reproduce, do you mean you can get some autocompletion on the Unit field?
The easiest way to reproduce doesn't even use external code. With this lib installed, go to node_modules/@aws-sdk/client-cloudwatch/dist-types/models/model_0.d.ts (which seems to be what's loaded up to get the types from), and hover over the Unit field (with VSCode for instance) in the MetricDatum interface. Despite being of type StandardUnit | string; the former is a string union as well, so the whole field gets coerced to string, removing any autocompletion for the field later down the line.
It is located here

aws-sdk-js-v3/clients/client-cloudwatch/src/models/models_0.ts

Line 3764 in f510f81

Unit?: StandardUnit | string;

So the two questions are:

1. can you get the right type + the autocompletion on your end for this field? (if yes then it's a VSCode bug and I'll report it there)
2. Can the Unit field be of a different value than a StandardUnit? (if no then it might be better to define it as just StandardUnit and not StandardUnit | string

It looks like this type union is being used in different places (DataPoint, MetricAlarm, etc.) so if it needs to be fixed, it should be in all these places as well.

[kuhe]

enums were closed in #5356

[github-actions]

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