[BUG] Telemetry correlation headers are not included for all fetch requests

[MSNev]

I am experiencing the same as @tcihak-fqa, and I have a similar setup.

After upgrading @microsoft/applicationinsights-web to v2.5.3 (from v2.4.4), correlation headers are missing in all fetch requests.

I tested to enable the new W3C distributed tracing mode

{
    // ...
    distributedTracingMode: DistributedTracingModes.W3C
    // ...
}

...still no correlation headers of any sort.
No other distributedTracingMode options seem to work either.

This must be a bug, it worked before upgrading.

@MSNev :
I'm running an ASP.NET core app with kestrel on https://localhost:5001.

No fetch polyfill is used (polyfill for fetch is dynamically loaded only if the browser does not have it natively - with the browser I use for testing the native fetch API is supported).

I use JS modules (traspiled from TypeScript) and import @microsoft/applicationinsights-web - it is included in webpack bundling from node_modules.

The HTML/CSS/JS code is hosted in the same web application; on the same domain/port as the API I'm calling with fetch (where the correlation headers are missing). No CORS should be required.

FYI: It made no difference to add "localhost:5001" to correlationHeaderDomains,

I had a few more configuration settings than in my code below, but I have tested stripping the configuration down to a minimum as follows and I still have the problem:

import { ApplicationInsights, DistributedTracingModes } from "@microsoft/applicationinsights-web";

// ...
            const ai = new ApplicationInsights({
                config: {
                    //correlationHeaderDomains: ["localhost:5001"], // Made no difference
                    instrumentationKey: "the-instrumentation-key",
                    disableAjaxTracking: false,
                    disableCorrelationHeaders: false,
                    disableFetchTracking: false,
                    distributedTracingMode: DistributedTracingModes.AI, // .AI_AND_W3C or .W3C also does not add any correlation headers
                }
            });

            ai.loadAppInsights();

@josundt I think I found the root cause for your issue, basically the code is adding the headers to the intercepted fetch request however if you don't pass the optional 2nd parameter (init), it creates one internally and populated the headers on this object... BUT, it doesn't pass this onto the real fetch!!!

As a workaround, if you pass a value as part of this 2nd parameter the headers should be sent correctly.

[MSNev]

Fixed deployed as NPM and next CDN channels

[MSNev]

Now also fully deployed to primary CDN

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