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package buildtags
import (
"bufio"
"bytes"
"fmt"
"go/format"
"strings"
)
// PlusBuildSyntaxSupported reports whether the current Go version supports the
// "// +build" constraint syntax.
func PlusBuildSyntaxSupported() bool { return plusbuild }
// GoBuildSyntaxSupported reports whether the current Go version supports the
// "//go:build" constraint syntax.
func GoBuildSyntaxSupported() bool { return gobuild }
// Format constraints according to the syntax supported by the current Go version.
func Format(t ConstraintsConvertable) (string, error) {
// Print build tags to minimal Go source that can be passed to go/format.
src := t.ToConstraints().GoString() + "\npackage stub"
// Format them.
formatted, err := format.Source([]byte(src))
if err != nil {
return "", fmt.Errorf("format build constraints: %w", err)
}
// Extract the comment lines.
buf := bytes.NewReader(formatted)
scanner := bufio.NewScanner(buf)
output := ""
for scanner.Scan() {
line := scanner.Text()
if (PlusBuildSyntaxSupported() && strings.HasPrefix(line, "// +build")) ||
(GoBuildSyntaxSupported() && strings.HasPrefix(line, "//go:build")) {
output += line + "\n"
}
}
if err := scanner.Err(); err != nil {
return "", fmt.Errorf("parse formatted build constraints: %w", err)
}
return output, nil
}
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