Add global propagator testing and other fixes (#1260)

* Add global propagator testing and other fixes

Use the testing framework from #1259 to test the added global
implementation of the TextMapPropagator.

Add tests for the internal state of the global package. Ensure the
behavior of setting the global for an already set value panics.

Fix oteltest `SetN` method check on the TextMapCarrier.

* Fix lint

api/global/internal/propagator_test.go

@@ -0,0 +1,108 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal_test
+
+import (
+	"context"
+	"testing"
+
+	"go.opentelemetry.io/otel/api/global/internal"
+	"go.opentelemetry.io/otel/oteltest"
+)
+
+func TestTextMapPropagatorDelegation(t *testing.T) {
+	internal.ResetForTest()
+	ctx := context.Background()
+	carrier := oteltest.NewTextMapCarrier(nil)
+
+	// The default should be a noop.
+	initial := internal.TextMapPropagator()
+	initial.Inject(ctx, carrier)
+	ctx = initial.Extract(ctx, carrier)
+	if !carrier.GotN(t, 0) || !carrier.SetN(t, 0) {
+		return
+	}
+
+	// Make sure the delegate woks as expected.
+	delegate := oteltest.NewTextMapPropagator("test")
+	delegate.Inject(ctx, carrier)
+	ctx = delegate.Extract(ctx, carrier)
+	if !delegate.InjectedN(t, carrier, 1) || !delegate.ExtractedN(t, ctx, 1) {
+		return
+	}
+
+	// The initial propagator should use the delegate after it is set as the
+	// global.
+	internal.SetTextMapPropagator(delegate)
+	initial.Inject(ctx, carrier)
+	ctx = initial.Extract(ctx, carrier)
+	delegate.InjectedN(t, carrier, 2)
+	delegate.ExtractedN(t, ctx, 2)
+}
+
+func TestTextMapPropagatorDelegationNil(t *testing.T) {
+	internal.ResetForTest()
+	ctx := context.Background()
+	carrier := oteltest.NewTextMapCarrier(nil)
+
+	// The default should be a noop.
+	initial := internal.TextMapPropagator()
+	initial.Inject(ctx, carrier)
+	ctx = initial.Extract(ctx, carrier)
+	if !carrier.GotN(t, 0) || !carrier.SetN(t, 0) {
+		return
+	}
+
+	// Delegation to nil should not make a change.
+	internal.SetTextMapPropagator(nil)
+	initial.Inject(ctx, carrier)
+	initial.Extract(ctx, carrier)
+	if !carrier.GotN(t, 0) || !carrier.SetN(t, 0) {
+		return
+	}
+}
+
+func TestTextMapPropagatorFields(t *testing.T) {
+	internal.ResetForTest()
+	initial := internal.TextMapPropagator()
+	delegate := oteltest.NewTextMapPropagator("test")
+	delegateFields := delegate.Fields()
+
+	// Sanity check on the initial Fields.
+	if got := initial.Fields(); fieldsEqual(got, delegateFields) {
+		t.Fatalf("testing fields (%v) matched Noop fields (%v)", delegateFields, got)
+	}
+	internal.SetTextMapPropagator(delegate)
+	// Check previous returns from global not correctly delegate.
+	if got := initial.Fields(); !fieldsEqual(got, delegateFields) {
+		t.Errorf("global TextMapPropagator.Fields returned %v instead of delegating, want (%v)", got, delegateFields)
+	}
+	// Check new calls to global.
+	if got := internal.TextMapPropagator().Fields(); !fieldsEqual(got, delegateFields) {
+		t.Errorf("global TextMapPropagator.Fields returned %v, want (%v)", got, delegateFields)
+	}
+}
+
+func fieldsEqual(f1, f2 []string) bool {
+	if len(f1) != len(f2) {
+		return false
+	}
+	for i := range f1 {
+		if f1[i] != f2[i] {
+			return false
+		}
+	}
+	return true
+}

api/global/internal/state.go

@@ -138,4 +138,5 @@ func ResetForTest() {
 	globalPropagators = defaultPropagatorsValue()
 	delegateMeterOnce = sync.Once{}
 	delegateTraceOnce = sync.Once{}
+	delegateTextMapPropagatorOnce = sync.Once{}
 }

api/global/internal/state_test.go

@@ -0,0 +1,50 @@
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package internal_test
+
+import (
+	"testing"
+
+	"go.opentelemetry.io/otel/api/global/internal"
+)
+
+func TestResetsOfGlobalsPanic(t *testing.T) {
+	internal.ResetForTest()
+	tests := map[string]func(){
+		"SetTextMapPropagator": func() {
+			internal.SetTextMapPropagator(internal.TextMapPropagator())
+		},
+		"SetTracerProvider": func() {
+			internal.SetTracerProvider(internal.TracerProvider())
+		},
+		"SetMeterProvider": func() {
+			internal.SetMeterProvider(internal.MeterProvider())
+		},
+	}
+
+	for name, test := range tests {
+		shouldPanic(t, name, test)
+	}
+}
+
+func shouldPanic(t *testing.T, name string, f func()) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("calling %s with default global did not panic", name)
+		}
+	}()
+
+	f()
+}

oteltest/text_map_propagator.go

@@ -111,7 +111,7 @@ func (c *TextMapCarrier) SetN(t *testing.T, n int) bool {
 	c.mtx.Lock()
 	defer c.mtx.Unlock()
 	if len(c.sets) != n {
-		t.Errorf("TextMapCarrier.Set was called %d times, not %d", len(c.gets), n)
+		t.Errorf("TextMapCarrier.Set was called %d times, not %d", len(c.sets), n)
 		return false
 	}
 	return true