gopls/internal/event/export/tag.go

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.
4
5	package export
6
7	import (
8	"context"
9
10	"golang.org/x/tools/internal/event"
11	"golang.org/x/tools/internal/event/core"
12	"golang.org/x/tools/internal/event/label"
13	)
14
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)
26	if stored == nil {
27	stored = fromEvent
28	} else {
29	stored = label.MergeMaps(fromEvent, stored)
30	}
31	ctx = context.WithValue(ctx, labelContextKey, stored)
32	}
33	// add the stored label context to the label map
34	lm = label.MergeMaps(lm, stored)
35	return output(ctx, ev, lm)
36	}
37	}
38

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