src/cmd/go/internal/imports/tags.go

// Copyright 2018 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 imports

import (
	"cmd/go/internal/cfg"
	"sync"
)

var (
	tags     map[string]bool
	tagsOnce sync.Once
)

// Tags returns a set of build tags that are true for the target platform.
// It includes GOOS, GOARCH, the compiler, possibly "cgo",
// release tags like "go1.13", and user-specified build tags.
func Tags() map[string]bool {
	tagsOnce.Do(func() {
		tags = loadTags()
	})
	return tags
}

func loadTags() map[string]bool {
	tags := map[string]bool{
		cfg.BuildContext.GOOS:     true,
		cfg.BuildContext.GOARCH:   true,
		cfg.BuildContext.Compiler: true,
	}
	if cfg.BuildContext.CgoEnabled {
		tags["cgo"] = true
	}
	for _, tag := range cfg.BuildContext.BuildTags {
		tags[tag] = true
	}
	for _, tag := range cfg.BuildContext.ToolTags {
		tags[tag] = true
	}
	for _, tag := range cfg.BuildContext.ReleaseTags {
		tags[tag] = true
	}
	return tags
}

var (
	anyTags     map[string]bool
	anyTagsOnce sync.Once
)

// AnyTags returns a special set of build tags that satisfy nearly all
// build tag expressions. Only "ignore" and malformed build tag requirements
// are considered false.
func AnyTags() map[string]bool {
	anyTagsOnce.Do(func() {
		anyTags = map[string]bool{"*": true}
	})
	return anyTags
}