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>

9 files changed, 28 insertions, 20 deletions

diff --git a/internal/event/core/event.go b/internal/event/core/event.go
index 2f979bdf1..29f293e62 100644
--- a/internal/event/core/event.go
+++ b/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
+}
diff --git a/internal/event/core/export.go b/internal/event/core/export.go
index f006ed14f..05f3a9a57 100644
--- a/internal/event/core/export.go
+++ b/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)
 }
diff --git a/internal/event/export/log.go b/internal/event/export/log.go
index cf1708ef5..93abae49e 100644
--- a/internal/event/export/log.go
+++ b/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)
diff --git a/internal/event/export/log_test.go b/internal/event/export/log_test.go
index c1f698842..8b553dbff 100644
--- a/internal/event/export/log_test.go
+++ b/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)
 	}
 }
diff --git a/internal/event/export/metric/exporter.go b/internal/event/export/metric/exporter.go
index 87563a41b..121b0ee1e 100644
--- a/internal/event/export/metric/exporter.go
+++ b/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))
 				}
 			}
 		}
diff --git a/internal/event/export/ocagent/ocagent.go b/internal/event/export/ocagent/ocagent.go
index b1396f9e5..46acca6f7 100644
--- a/internal/event/export/ocagent/ocagent.go
+++ b/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),
 	}
 }
diff --git a/internal/event/export/ocagent/ocagent_test.go b/internal/event/export/ocagent/ocagent_test.go
index fa88f35d5..0979f530b 100644
--- a/internal/event/export/ocagent/ocagent_test.go
+++ b/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)
 	}
diff --git a/internal/lsp/debug/rpc.go b/internal/lsp/debug/rpc.go
index de90a6cf3..f15f6cabb 100644
--- a/internal/lsp/debug/rpc.go
+++ b/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
diff --git a/internal/lsp/debug/trace.go b/internal/lsp/debug/trace.go
index 8213df758..36dd530f6 100644
--- a/internal/lsp/debug/trace.go
+++ b/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),
 			}
 		}