| // Copyright 2019 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package export |
| |
| import ( |
| "context" |
| |
| "golang.org/x/tools/internal/telemetry/event" |
| ) |
| |
| // Labels builds an exporter that manipulates the context using the event. |
| // If the event is type IsTag or IsStartSpan then it returns a context updated |
| // with tag values from the event. |
| // For all other event types the event tags will be updated with values from the |
| // context if they are missing. |
| func Labels(output event.Exporter) event.Exporter { |
| return func(ctx context.Context, ev event.Event, tagMap event.TagMap) context.Context { |
| stored, _ := ctx.Value(labelContextKey).(event.TagMap) |
| if ev.IsLabel() || ev.IsStartSpan() { |
| // update the tag source stored in the context |
| fromEvent := ev.Map() |
| if stored == nil { |
| stored = fromEvent |
| } else { |
| stored = event.MergeTagMaps(fromEvent, stored) |
| } |
| ctx = context.WithValue(ctx, labelContextKey, stored) |
| } |
| // add the stored tag context to the tag source |
| tagMap = event.MergeTagMaps(tagMap, stored) |
| return output(ctx, ev, tagMap) |
| } |
| } |