pkg/etw: Fix to build on windows/arm

We don't support actually using ETW on windows/arm, but to make things
easier for downstream dependencies, we want to still allow the package
to compile and just no-op on this architecture. We do this by returning
a nil Provider, and implementing its methods to no-op when the receiver
is nil.

Previously this was implemented by putting NewProviderWithID in
provider_unsupported.go, but when we refactored the code so that the
actual work was done in NewProviderWithOptions instead, we didn't fix up
provider_unsupported. This change fixes this by putting only
NewProviderWithOptions in provider_unsupported.go, since the other
provider creation functions call into this one.

Signed-off-by: Kevin Parsons <kevpar@microsoft.com>

pkg/etw/provider.go

@@ -119,6 +119,46 @@ func providerIDFromName(name string) guid.GUID {
 	return guid.FromWindowsArray(a)
 }
 
+type providerOpts struct {
+	callback EnableCallback
+	id       guid.GUID
+	group    guid.GUID
+}
+
+// ProviderOpt allows the caller to specify provider options to
+// NewProviderWithOptions
+type ProviderOpt func(*providerOpts)
+
+// WithCallback is used to provide a callback option to NewProviderWithOptions
+func WithCallback(callback EnableCallback) ProviderOpt {
+	return func(opts *providerOpts) {
+		opts.callback = callback
+	}
+}
+
+// WithID is used to provide a provider ID option to NewProviderWithOptions
+func WithID(id guid.GUID) ProviderOpt {
+	return func(opts *providerOpts) {
+		opts.id = id
+	}
+}
+
+// WithGroup is used to provide a provider group option to
+// NewProviderWithOptions
+func WithGroup(group guid.GUID) ProviderOpt {
+	return func(opts *providerOpts) {
+		opts.group = group
+	}
+}
+
+// NewProviderWithID creates and registers a new ETW provider, allowing the
+// provider ID to be manually specified. This is most useful when there is an
+// existing provider ID that must be used to conform to existing diagnostic
+// infrastructure.
+func NewProviderWithID(name string, id guid.GUID, callback EnableCallback) (provider *Provider, err error) {
+	return NewProviderWithOptions(name, WithID(id), WithCallback(callback))
+}
+
 // NewProvider creates and registers a new ETW provider. The provider ID is
 // generated based on the provider name.
 func NewProvider(name string, callback EnableCallback) (provider *Provider, err error) {