Add Exception field to ETW logging event

[rosebyte]

Fixes #43092

add Exception field to ETW event

[Copilot]

Pull request overview

Adds exception text to the FormattedMessage ETW event emitted by Microsoft.Extensions.Logging.EventSource, so consumers of the formatted-message keyword can also see exception details.

Changes:

• Extend LoggingEventSource.FormattedMessage (EventId 1) payload to include an Exception string field and bump event version.
• Update EventSourceLogger to pass exception?.ToString() (or empty string) into the formatted-message event.
• Adjust existing tests to validate the new Exception field presence for formatted-message events.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/libraries/Microsoft.Extensions.Logging.EventSource/src/LoggingEventSource.cs	Adds Exception to the FormattedMessage event payload and bumps event version.
src/libraries/Microsoft.Extensions.Logging.EventSource/src/EventSourceLogger.cs	Populates the new Exception payload field when emitting formatted-message events.
src/libraries/Microsoft.Extensions.Logging.EventSource/tests/EventSourceLoggerTest.cs	Updates expectations to include the new Exception field in formatted-message event JSON.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Logging.EventSource/src/LoggingEventSource.cs:163

• FormattedMessage treats EventName/FormattedMessage as nullable and normalizes them to string.Empty, but the new Exception parameter is non-nullable and only guarded by Debug.Assert. For consistency and to avoid a potential NullReferenceException in release builds if any future caller passes null, consider making Exception nullable and normalizing it like the other optional strings.

            string? EventName,
            string? FormattedMessage,
            string ActivityTraceId,
            string ActivitySpanId,
            string ActivityTraceFlags,
            string Exception)
        {
            Debug.Assert(LoggerName != null);
            Debug.Assert(ActivityTraceId != null);
            Debug.Assert(ActivitySpanId != null);
            Debug.Assert(ActivityTraceFlags != null);
            Debug.Assert(Exception != null);

            EventName ??= string.Empty;
            FormattedMessage ??= string.Empty;

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