1 // Copyright 2019 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
10 "golang.org/x/tools/internal/event"
11 "golang.org/x/tools/internal/event/core"
12 "golang.org/x/tools/internal/event/label"
15 // Labels builds an exporter that manipulates the context using the event.
16 // If the event is type IsLabel or IsStartSpan then it returns a context updated
17 // with label values from the event.
18 // For all other event types the event labels will be updated with values from the
19 // context if they are missing.
20 func Labels(output event.Exporter) event.Exporter {
21 return func(ctx context.Context, ev core.Event, lm label.Map) context.Context {
22 stored, _ := ctx.Value(labelContextKey).(label.Map)
23 if event.IsLabel(ev) || event.IsStart(ev) {
24 // update the label map stored in the context
25 fromEvent := label.Map(ev)
29 stored = label.MergeMaps(fromEvent, stored)
31 ctx = context.WithValue(ctx, labelContextKey, stored)
33 // add the stored label context to the label map
34 lm = label.MergeMaps(lm, stored)
35 return output(ctx, ev, lm)