Metric Search with Namespace and Dimensions are wrongly wrapped with white spaces

[dgmezan-amzn]

Version

v8.3.6

Steps and/or minimal code example to reproduce

1. Emit metrics on a custom namespace (e.g. my_custom_namespace).
2. Create a CustomMetricSearch, using as namespace the custom namespace along with a dimension. For example

const myCustomMetricSearch: CustomMetricSearch = {
  namespace: "my_custom_namespace,reason"
  searchQuery: "MY.CUSTOM.METRIC",
  dimensionsMap: {},
  statistic: MetricStatistic.SUM,
  label: "${PROP('Dim.reason')} (sum: ${SUM})"
}

Expected behavior

When this gets deployed to CloudWatch, what I see is the following:

...
"metrics": [
        [ { "label": "${PROP('Dim.reason')} (sum: ${SUM})", "expression": "SEARCH('{\"my_custom_namespace,reason\"}  MY.CUSTOM.METRIC', 'Sum', 60)", "period": 60 } ]
    ],

Actual behavior

When this gets deployed to CloudWatch, what I should see is the following:

...
"metrics": [
        [ { "label": "${PROP('Dim.reason')} (sum: ${SUM})", "expression": "SEARCH('{\"my_custom_namespace\",\"reason\"}  MY.CUSTOM.METRIC', 'Sum', 60)", "period": 60 } ]
    ],

or

...
"metrics": [
        [ { "label": "${PROP('Dim.reason')} (sum: ${SUM})", "expression": "SEARCH('{my_custom_namespace,reason}  MY.CUSTOM.METRIC', 'Sum', 60)", "period": 60 } ]
    ],

Other details

This was caused by #591. I've downgraded to the previous version and it works as expected with it.

I take it what you've written under the "Expected behavior" and "Actual behavior" are actually flipped?

This is indeed a bug if the expectation was to allow multiple namespaces like that; would you be willing to send a PR with a fix?