Introduce a new internal EventSourceGenerator and use it for all ES implementations #121180

EgorBo · 2025-10-29T18:13:45Z

Remove [EventSourceAutoGenerate], we rely on just [EventSource] + no explicit ctors
Introduce a new global SourceGenerators - EventSourceGenerator (and move the existing impl from SPC.Generators to this new project)
Update slnx files (via the UpdateSolutionFiles task)
Migrate all classes with [EventSource] to use the SG. Except for the ones with EventSourceSettings.EtwSelfDescribingEventFormat -- there are 3 ES impl defining this settings 🤔

EgorBo · 2025-10-29T18:15:22Z

hm.. probably should move the SLNX update to a separate (last) commit (or maybe even PR?)

…+ no explicit ctors 2) Introduce a new global SourceGenerators - EventSourceGenerator (and move the existing impl from SPC.Generators to this new project) 3) Update slnx files (via the UpdateSolutionFiles task) 4) Migrate all classes with [EventSource] to use the SG. Except for the ones with EtwSelfDescribingEventFormat

stephentoub · 2025-10-29T18:20:47Z

we rely on just [EventSource] + no explicit ctors

We will likely want more than just this, e.g. it'll need to be partial.

stephentoub · 2025-10-29T18:21:27Z

Update slnx files

Do we need to modify the slnx files? Could we instead globally include via .props?

EgorBo · 2025-10-29T18:31:39Z

Update slnx files

Do we need to modify the slnx files? Could we instead globally include via .props?

it's not needed to build the projects, but needed for people opening slnx files for the SG project to show up there in slnx. All other source generator projects are already added there (added automatically by the UpdateSolutionFile task, which is manually invoked (it's slow))

jkotas · 2025-10-29T21:30:33Z

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Parser.cs

+                        }
+                    }
+                }
+


Can we generate warning when we run into EventSource that we are not able to generate the ctor for?

@jkotas we have 3 that we can't generate for:

Microsoft.Extensions.DependencyInjection\src\DependencyInjectionEventSource.cs

Microsoft.Extensions.Logging.EventSource\src\LoggingEventSource.cs

System.Diagnostics.DiagnosticSource\src\System\Diagnostics\DiagnosticSourceEventSource.cs

they need to pass EventSourceSettings.EtwSelfDescribingEventFormat to the settings argument.

We have 3 options:

Propose an API to add EventSourceSettings to the [EventSource] arg so we can define it there (and use from the SG)

Leave some internal hint for the SG that we need EtwSelfDescribingEventFormat instead of the default (e.g. some constant field?)

Leave these 3 as is

cc @stephentoub @noahfalk

they need to pass EventSourceSettings.EtwSelfDescribingEventFormat to the settings argument.

Why do these need to pass EventSourceSettings.EtwSelfDescribingEventFormat?

I would like to understand whether EtwSelfDescribingEventFormat is a corner-case that is only used in handful of places in runtime repo (3 is ok in that case), or whether it is something that gets used reasonably often (1 is worth doing in that case).

Similar concern about the other EventSource ctor arguments. How often are they used in practice? If they are used reasonably often, we may want to do some sort of extended version of (1).

I would like to understand whether EtwSelfDescribingEventFormat is a corner-case that is only used in handful of places in runtime repo (3 is ok in that case), or whether it is something that gets used reasonably often (1 is worth doing in that case).

I'm afraid I don't know, perhaps someone from @dotnet/dotnet-diag can answer?

I also noticed there is an inconsistency among the base EventSource constructors:

protected EventSource() { } // EtwManifestEventFormat protected EventSource(bool) { } // EtwManifestEventFormat public EventSource(string) { } // EtwSelfDescribingEventFormat public EventSource(string, Guid) { } // EtwManifestEventFormat`

so in the end, it does look like we only have 3 ES that uses EtwSelfDescribingEventFormat

Why do these need to pass EventSourceSettings.EtwSelfDescribingEventFormat?

DependencyInjectionEventSource - looks compatible with both formats. Changing from SelfDescribing to Manifest could prevent the EventSource from working properly with ETW profilers that don't use the TraceEvent library to abstract the data parsing

LoggingEventSource and DiagnosticSourceEventSource - Use IEnumerable<T> as an event parameter type which is only supported by SelfDescribingFormat

I would like to understand whether EtwSelfDescribingEventFormat is a corner-case that is only used in handful of places in runtime repo (3 is ok in that case), or whether it is something that gets used reasonably often (1 is worth doing in that case).

SelfDescribing is more than a corner case for 3P usage - it has more capabilities and better compatibility with ETW profilers that don't use the TraceEvent library. However it has higher per-event serialization overhead which is why most of our runtime EventSources don't use it.

Similar concern about the other EventSource ctor arguments. How often are they used in practice? If they are used reasonably often, we may want to do some sort of extended version of (1).

Aside from name, Guid, and EventSourceSettings enum there are only two other ctor arguments:

bool throwOnEventWriteErrors - this is superceded by EventSourceSettings so no reason to include it separately

string[] traits - Arbitrary key value pairs that can be associated with an EventSource. I don't recall seeing a real-world use. I believe it is rare but its not easy to back that up with simple code search results because both 'EventSource' and 'traits' find huge numbers of unrelated references.

I like (1)

Ditto 👍

Ok, then let's put the PR on pause till the API proposal lands

I do not think you need to wait for that API proposal to land. You can leave the 3 event sources that need that API proposal alone (disable the warning for them), and deal with the rest.

@jkotas ok, then I guess it's ready for review

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Emitter.cs

src/libraries/System.Threading/src/System/Threading/CDSsyncETWBCLProvider.cs

src/libraries/System.Transactions.Local/src/System/Transactions/TransactionsEtwProvider.cs

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Emitter.cs

Copilot

Pull Request Overview

This PR introduces a source generator for EventSource classes to automatically generate constructors and metadata, eliminating the need for manual boilerplate code. The generator creates parameterless constructors that call the base EventSource constructor with the correct parameter order (name, guid).

Key changes:

Introduces EventSourceGenerator source generator that triggers on classes with [EventSource] attribute
Removes [EventSourceAutoGenerate] attribute and makes affected EventSource classes partial
Changes EventSource base constructor parameter order from (Guid, string) to (string, Guid) for consistency
Removes manual constructors from EventSource classes across the codebase

Reviewed Changes

Copilot reviewed 50 out of 50 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
EventSourceGenerator.cs	New source generator that creates constructors for EventSource classes
EventSourceGenerator.Parser.cs	Parser logic to extract EventSource metadata and validate constructors
EventSourceGenerator.Emitter.cs	Code generation logic for constructors and provider metadata
EventSource.cs	Changes constructor parameter order and visibility for source generator
TraceLoggingEventSource.cs	Updates constructor call to match new parameter order
Multiple EventSource classes	Removes manual constructors and adds `partial` keyword
NetCoreAppLibrary.props	Registers EventSourceGenerator
generators.targets	Enables generator for source projects
Directory.Build.props	Suppresses ESGEN001 warnings globally

Comments suppressed due to low confidence (1)

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Parser.cs:24

The parser only checks for NamespaceDeclarationSyntax but doesn't check for FileScopedNamespaceDeclarationSyntax. This will cause the generator to skip classes in file-scoped namespaces. Use BaseNamespaceDeclarationSyntax as the base type to handle both traditional and file-scoped namespace declarations.

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Parser.cs

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Emitter.cs

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Parser.cs

src/libraries/System.Net.Http/src/System/Net/Http/HttpTelemetry.cs

stephentoub · 2025-11-05T01:34:28Z

src/libraries/Microsoft.Extensions.DependencyInjection/src/DependencyInjectionEventSource.cs


        private readonly List<WeakReference<ServiceProvider>> _providers = new();

+#pragma warning disable ESGEN001 // EventSource classes should not declare constructors.


Is there a tracking issue for these?

stephentoub · 2025-11-05T01:35:38Z

src/libraries/System.Diagnostics.Tracing/tests/BasicEventSourceTest/ActivityTracking.cs

    [EventSource(Name = "ActivityEventSource")]
    class ActivityEventSource : EventSource
    {
+        public ActivityEventSource() { }


Why was this necessary?

jkotas

Thoughts on what it would take to make this source generator part of the SDK?

jkotas · 2025-11-05T03:39:00Z

src/libraries/Microsoft.Extensions.DependencyInjection/src/DependencyInjectionEventSource.cs

        private readonly List<WeakReference<ServiceProvider>> _providers = new();

+#pragma warning disable ESGEN001 // EventSource classes should not declare constructors.
        private DependencyInjectionEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)


Suggested change

private DependencyInjectionEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

// Uses EtwSelfDescribingEventFormat for backward compatibility

private DependencyInjectionEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

Capture insights from PR comments

jkotas · 2025-11-05T03:41:16Z

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

        private static readonly char[] s_colon = new[] { ':' };

+#pragma warning disable ESGEN001 // EventSource classes should not declare constructors.
        private LoggingEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)


Suggested change

private LoggingEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

// This event source uses IEnumerable<T> as an event parameter type which is only supported by SelfDescribingFormat

private LoggingEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

jkotas · 2025-11-05T03:42:57Z

...es/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/DiagnosticSourceEventSource.cs

        private DiagnosticSourceEventSource()
            // This constructor uses EventSourceSettings which is only available on V4.6 and above
            // Use the EventSourceSettings to turn on support for complex types, if available (v4.6 and above).
            : base(DiagnosticSourceEventSourceName, EventSourceSettings.EtwSelfDescribingEventFormat)


Suggested change

private DiagnosticSourceEventSource()

// This constructor uses EventSourceSettings which is only available on V4.6 and above

// Use the EventSourceSettings to turn on support for complex types, if available (v4.6 and above).

: base(DiagnosticSourceEventSourceName, EventSourceSettings.EtwSelfDescribingEventFormat)

// This event source uses IEnumerable<T> as an event parameter type which is only supported by SelfDescribingFormat

private DiagnosticSourceEventSource() : base(DiagnosticSourceEventSourceName, EventSourceSettings.EtwSelfDescribingEventFormat)

jkotas · 2025-11-05T03:45:31Z

src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Parser.cs

+                                new DiagnosticDescriptor(
+                                    "ESGEN001",
+                                    "EventSource class contains explicit constructor",
+                                    "EventSource class '{0}' contains an explicit constructor. EventSource classes must not declare constructors.",


Suggested change

"EventSource class '{0}' contains an explicit constructor. EventSource classes must not declare constructors.",

"EventSource class '{0}' contains an explicit constructor. EventSource classes must not declare constructors to take advantage of this source generator.",

?

github-actions bot added the needs-area-label An area label is needed to ensure this gets routed to the appropriate area owners label Oct 29, 2025

EgorBo changed the title ~~Es cleanup~~ Introduce a new internal EventSourceGenerator and use it for all ES implementations Oct 29, 2025

EgorBo force-pushed the ES-cleanup branch from ae857c0 to 21f579b Compare October 29, 2025 18:19

jkotas reviewed Oct 29, 2025

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EgorBo added 4 commits October 29, 2025 23:15

Merge branch 'main' into ES-cleanup

c4cf897

fix build

f5dbdd2

Merge branch 'ES-cleanup' of github.com:EgorBo/runtime-1 into ES-cleanup

c702892

cleanup

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This was referenced Oct 30, 2025

The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

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[browser] Wasm.Build.Tests timeout - Timed out after 10s waiting for 'WASM EXIT' #116697

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[QUIC] Sporadic long running tests #119763

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EgorBo mentioned this pull request Oct 30, 2025

[API Proposal]: Settings property in EventSourceAttribute #121205

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src/libraries/System.Private.CoreLib/gen/EventSourceGenerator.Emitter.cs Outdated Show resolved Hide resolved

Copilot AI mentioned this pull request Nov 1, 2025

Add performance and compatibility details to EtwManifestEventFormat and EtwSelfDescribingEventFormat docs dotnet/dotnet-api-docs#12000

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EgorBo added 2 commits November 4, 2025 16:42

Merge branch 'main' of https://github.com/dotnet/runtime into ES-cleanup

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Address feedback

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Introduce a warning

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EgorBo marked this pull request as ready for review November 4, 2025 22:45

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feedback

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Merge branch 'main' of https://github.com/dotnet/runtime into ES-cleanup

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AppHost test failure: I/O failure when writing extracted files #120653

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		private readonly List<WeakReference<ServiceProvider>> _providers = new();

		#pragma warning disable ESGEN001 // EventSource classes should not declare constructors.

	private DependencyInjectionEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)
	// Uses EtwSelfDescribingEventFormat for backward compatibility
	private DependencyInjectionEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

	private LoggingEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)
	// This event source uses IEnumerable<T> as an event parameter type which is only supported by SelfDescribingFormat
	private LoggingEventSource() : base(EventSourceSettings.EtwSelfDescribingEventFormat)

	"EventSource class '{0}' contains an explicit constructor. EventSource classes must not declare constructors.",
	"EventSource class '{0}' contains an explicit constructor. EventSource classes must not declare constructors to take advantage of this source generator.",

Introduce a new internal EventSourceGenerator and use it for all ES implementations #121180

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Introduce a new internal EventSourceGenerator and use it for all ES implementations #121180

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