[Azure.Core] Test Environment Exception When Optional Environment Variable Not Set

[jsquire]

Observed Behavior

The TestEnvironment::GetRecordedOptionalVariable method reads the value of the environment variable, which may be null when not defined. That value is then passed into the RecordedVariableOptions when specified which attempts to parse the value using the ConnectionString type, causing an exception when validated due to the connection string value itself being null.

This was observed in the Service Bus library, when it's ServiceBusTestEnvironment::OverrideServiceBusConnectionString is not set.

Expected Behavior

• Optional environment variables do not need to be set and do not result in an exception when null.
• Using GetRecordedOptionalVariable with an optional environment variable is safe.

Implementation Thoughts

It looks as if the most appropriate place to adjust behavior would either be within the TestEnvironment, where null or empty values are not passed to the RecordedVariableOptions or within the options, adding a null or empty check before processing the connection string. I'm not sure of the intent for having overrides or extensions to RecordedVariableOptions where it may be desirable to invoke regardless of value.

[jsquire]

@pakrym: If you can help me understand a bit more about the intention of RecordedVariableOptions, I'm happy to make the fix.

[pakrym]

The intent of RecordedVariableOptions is for consumers to be able to describe what secrets are inside the value of the variable so we can sanitize them before storing it.

In this case skipping the entire code-path when no variable exists seems the right thing to do.

[jsquire]

Fixed By #14906