fix(otelgrpc): prevent panic when nil TracerProvider or MeterProvider is passed

Commit 07504e4 removed nil checks from WithTracerProvider and
WithMeterProvider, causing a panic when callers pass nil. This restores
the checks so nil values are ignored and the global provider is used.

Signed-off-by: Davanum Srinivas <[email protected]>

Author: dims

CHANGELOG.md

@@ -12,6 +12,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 - Change `Version()` function in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp` to a `const Version` string. (#8142)
 
+### Fixed
+
+- Fix panic when passing nil `TracerProvider` or `MeterProvider` to `WithTracerProvider` or `WithMeterProvider` in `go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc`. (#8323)
+
 ### Removed
 
 - The deprecated `DefaultClient`, `Get`, `Head`, `Post`, and `PostForm` in `go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp`.

instrumentation/google.golang.org/grpc/otelgrpc/config.go

@@ -125,15 +125,19 @@ func WithFilter(f Filter) Option {
 // creating a Tracer.
 func WithTracerProvider(tp trace.TracerProvider) Option {
 	return optionFunc(func(c *config) {
-		c.TracerProvider = tp
+		if tp != nil {
+			c.TracerProvider = tp
+		}
 	})
 }
 
 // WithMeterProvider returns an Option to use the MeterProvider when
 // creating a Meter. If this option is not provide the global MeterProvider will be used.
 func WithMeterProvider(mp metric.MeterProvider) Option {
 	return optionFunc(func(c *config) {
-		c.MeterProvider = mp
+		if mp != nil {
+			c.MeterProvider = mp
+		}
 	})
 }
 

instrumentation/google.golang.org/grpc/otelgrpc/stats_handler_test.go

@@ -165,6 +165,37 @@ func TestWithPublicEndpointFn(t *testing.T) {
 	}
 }
 
+func TestNilProviderOption(t *testing.T) {
+	// Passing a nil TracerProvider or MeterProvider should not panic and
+	// should use the global provider instead.
+	t.Run("nil TracerProvider", func(t *testing.T) {
+		assert.NotPanics(t, func() {
+			_ = NewClientHandler(WithTracerProvider(nil))
+		})
+		assert.NotPanics(t, func() {
+			_ = NewServerHandler(WithTracerProvider(nil))
+		})
+	})
+
+	t.Run("nil MeterProvider", func(t *testing.T) {
+		assert.NotPanics(t, func() {
+			_ = NewClientHandler(WithMeterProvider(nil))
+		})
+		assert.NotPanics(t, func() {
+			_ = NewServerHandler(WithMeterProvider(nil))
+		})
+	})
+
+	t.Run("both nil", func(t *testing.T) {
+		assert.NotPanics(t, func() {
+			_ = NewClientHandler(WithTracerProvider(nil), WithMeterProvider(nil))
+		})
+		assert.NotPanics(t, func() {
+			_ = NewServerHandler(WithTracerProvider(nil), WithMeterProvider(nil))
+		})
+	})
+}
+
 func TestNilInstruments(t *testing.T) {
 	mp := meterProvider{}
 	opts := []Option{WithMeterProvider(mp)}