internal/event: change event.At to be a private field

This was the last piece of Event that was public, and it was only public to
allow mutation in tests.
Adding CloneEvent allows tests to create an updated copy rather than
update the event in place.

Change-Id: I2215d1eb0317063948ef0fac955fa768a209564d
Reviewed-on: https://go-review.googlesource.com/c/tools/+/229241
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

internal/event/core/event.go

@@ -26,7 +26,7 @@ const (
 
 // Event holds the information about an event of note that ocurred.
 type Event struct {
-	At time.Time
+	at time.Time
 
 	typ eventType
 
@@ -47,6 +47,8 @@ type eventLabelMap struct {
 	event Event
 }
 
+func (ev Event) At() time.Time { return ev.at }
+
 func (ev Event) IsLog() bool       { return ev.typ == LogType }
 func (ev Event) IsEndSpan() bool   { return ev.typ == EndSpanType }
 func (ev Event) IsStartSpan() bool { return ev.typ == StartSpanType }
@@ -55,8 +57,8 @@ func (ev Event) IsDetach() bool    { return ev.typ == DetachType }
 func (ev Event) IsRecord() bool    { return ev.typ == RecordType }
 
 func (ev Event) Format(f fmt.State, r rune) {
-	if !ev.At.IsZero() {
-		fmt.Fprint(f, ev.At.Format("2006/01/02 15:04:05 "))
+	if !ev.at.IsZero() {
+		fmt.Fprint(f, ev.at.Format("2006/01/02 15:04:05 "))
 	}
 	for index := 0; ev.Valid(index); index++ {
 		l := ev.Label(index)
@@ -96,3 +98,9 @@ func MakeEvent(typ eventType, static [3]label.Label, labels []label.Label) Event
 		dynamic: labels,
 	}
 }
+
+// CloneEvent event returns a copy of the event with the time adjusted to at.
+func CloneEvent(ev Event, at time.Time) Event {
+	ev.at = at
+	return ev
+}

internal/event/core/export.go

@@ -40,7 +40,7 @@ func SetExporter(e Exporter) {
 // it will fill in the time.
 func deliver(ctx context.Context, exporter Exporter, ev Event) context.Context {
 	// add the current time to the event
-	ev.At = time.Now()
+	ev.at = time.Now()
 	// hand the event off to the current exporter
 	return exporter(ctx, ev, ev)
 }

internal/event/export/log.go

@@ -42,8 +42,8 @@ func (w *logWriter) ProcessEvent(ctx context.Context, ev core.Event, lm label.Ma
 		defer w.mu.Unlock()
 
 		buf := w.buffer[:0]
-		if !ev.At.IsZero() {
-			w.writer.Write(ev.At.AppendFormat(buf, "2006/01/02 15:04:05 "))
+		if !ev.At().IsZero() {
+			w.writer.Write(ev.At().AppendFormat(buf, "2006/01/02 15:04:05 "))
 		}
 		msg := keys.Msg.Get(lm)
 		io.WriteString(w.writer, msg)

internal/event/export/log_test.go

@@ -34,7 +34,7 @@ func ExampleLog() {
 func timeFixer(output event.Exporter) event.Exporter {
 	at, _ := time.Parse(time.RFC3339Nano, "2020-03-05T14:27:48Z")
 	return func(ctx context.Context, ev core.Event, lm label.Map) context.Context {
-		ev.At = at
-		return output(ctx, ev, lm)
+		copy := core.CloneEvent(ev, at)
+		return output(ctx, copy, lm)
 	}
 }

internal/event/export/metric/exporter.go

@@ -48,7 +48,7 @@ func (e *Config) Exporter(output event.Exporter) event.Exporter {
 			id := l.Key()
 			if list := e.subscribers[id]; len(list) > 0 {
 				for _, s := range list {
-					metrics = append(metrics, s(ev.At, lm, l))
+					metrics = append(metrics, s(ev.At(), lm, l))
 				}
 			}
 		}

internal/event/export/ocagent/ocagent.go

@@ -200,8 +200,8 @@ func convertSpan(span *export.Span) *wire.Span {
 		ParentSpanID:            span.ParentID[:],
 		Name:                    toTruncatableString(span.Name),
 		Kind:                    wire.UnspecifiedSpanKind,
-		StartTime:               convertTimestamp(span.Start().At),
-		EndTime:                 convertTimestamp(span.Finish().At),
+		StartTime:               convertTimestamp(span.Start().At()),
+		EndTime:                 convertTimestamp(span.Finish().At()),
 		Attributes:              convertAttributes(label.Filter(span.Start(), keys.Name)),
 		TimeEvents:              convertEvents(span.Events()),
 		SameProcessAsParentSpan: true,
@@ -307,7 +307,7 @@ func convertEvents(events []core.Event) *wire.TimeEvents {
 
 func convertEvent(ev core.Event) wire.TimeEvent {
 	return wire.TimeEvent{
-		Time:       convertTimestamp(ev.At),
+		Time:       convertTimestamp(ev.At()),
 		Annotation: convertAnnotation(ev),
 	}
 }

internal/event/export/ocagent/ocagent_test.go

@@ -130,11 +130,11 @@ func timeFixer(output event.Exporter) event.Exporter {
 	return func(ctx context.Context, ev core.Event, lm label.Map) context.Context {
 		switch {
 		case ev.IsStartSpan():
-			ev.At = start
+			ev = core.CloneEvent(ev, start)
 		case ev.IsEndSpan():
-			ev.At = end
+			ev = core.CloneEvent(ev, end)
 		default:
-			ev.At = at
+			ev = core.CloneEvent(ev, at)
 		}
 		return output(ctx, ev, lm)
 	}

internal/lsp/debug/rpc.go

@@ -128,7 +128,7 @@ func endRPC(ctx context.Context, ev core.Event, span *export.Span, stats *rpcSta
 	}
 
 	// calculate latency if this was an rpc span
-	elapsedTime := span.Finish().At.Sub(span.Start().At)
+	elapsedTime := span.Finish().At().Sub(span.Start().At())
 	latencyMillis := timeUnits(elapsedTime) / timeUnits(time.Millisecond)
 	if stats.Latency.Count == 0 {
 		stats.Latency.Min = latencyMillis

internal/lsp/debug/trace.go

@@ -94,7 +94,7 @@ func (t *traces) ProcessEvent(ctx context.Context, ev core.Event, lm label.Map)
 			SpanID:   span.ID.SpanID,
 			ParentID: span.ParentID,
 			Name:     span.Name,
-			Start:    span.Start().At,
+			Start:    span.Start().At(),
 			Tags:     renderLabels(span.Start()),
 		}
 		t.unfinished[span.ID] = td
@@ -118,13 +118,13 @@ func (t *traces) ProcessEvent(ctx context.Context, ev core.Event, lm label.Map)
 		}
 		delete(t.unfinished, span.ID)
 
-		td.Finish = span.Finish().At
-		td.Duration = span.Finish().At.Sub(span.Start().At)
+		td.Finish = span.Finish().At()
+		td.Duration = span.Finish().At().Sub(span.Start().At())
 		events := span.Events()
 		td.Events = make([]traceEvent, len(events))
 		for i, event := range events {
 			td.Events[i] = traceEvent{
-				Time: event.At,
+				Time: event.At(),
 				Tags: renderLabels(event),
 			}
 		}