Populate required field Message with n/a if it is empty

[NeilMountford]

Fix Issue #1066.

Changes

Application Insights rejects exceptions that have empty messages. This means that some exceptions are lost, making investigation of runtime issues difficult. I noticed this when investigating an issue in a .NET 8 API, where a CosmosException for a conflict occurred, was logged on the console but wasn't logged in App Insights.

There was previously a PR #2697 that never got merged due to lack of tests.

Original example from the other PR:

var configuration = TelemetryConfiguration.CreateDefault();
configuration.ConnectionString = "InstrumentationKey=...";
var telemetryClient = new TelemetryClient(configuration);
telemetryClient.TrackException(new Exception("")); // ignored
telemetryClient.TrackException(new Exception("foo")); // logged
telemetryClient.Flush();

Original response from the other PR:

{
    "itemsReceived": 1,
    "itemsAccepted": 0,
    "errors":
    [
        {
            "index": 0,
            "statusCode": 400,
            "message": "109: Field 'message' on type 'ExceptionDetails' is required but missing or empty. Expected: string, Actual: undefined"
        }
    ]
}

Checklist

• [✅] I ran Unit Tests locally.*
• [✅] CHANGELOG.md updated with one line description of the fix, and a link to the original issue if available.

• I had some test failures on a fresh clone, but the tests for the relevant part of the code were passing, so I'm hoping it's just an issue with some dependencies on my machine.

For significant contributions please make sure you have completed the following items:

• [N/A] Design discussion issue #
• [N/A] Changes in public surface reviewed

The PR will trigger build, unit tests, and functional tests automatically. Please follow these instructions to build and test locally.

Notes for authors:

• FxCop and other analyzers will fail the build. To see these errors yourself, compile localy using the Release configuration.

[NeilMountford]

@microsoft-github-policy-service agree

[cijothomas]

Thanks, this looks good!

Will ask one more owner to review before merge, as we are adding limited additions (including fixes) to this repo.

[NeilMountford]

Thanks @cijothomas, I've pushed a further change to move using Microsoft.ApplicationInsights.DataContracts; into the namespace block to make the build happy for the net4* builds - apologies for not catching this locally, I don't have access to a Windows machine currently. Could you approve the workflows again please? 🙂

[TimothyMothra]

please address comments

[TimothyMothra]

LGTM

[NeilMountford]

@TimothyMothra What are the next steps to get this merged/released? Let me know if you need anything from me 🙂

[cijothomas]

@TimothyMothra What are the next steps to get this merged/released? Let me know if you need anything from me 🙂

Merged!
We don't have a planned date for the next release.

[jiilaa]

So, half a year since this fix was merged (and even longer since the latest release for this library), maybe a good time for a release? :)

[asos-AdamCox]

@TimothyMothra / @cijothomas any chance of a release? We've just spent an entire day chasing this bug down only to find it was found in 2019, fixed 7 months ago and still not released...