in internal/encoding/json/indent.go [126:182]
func appendIndent(dst, src []byte, prefix, indent string) ([]byte, error) {
origLen := len(dst)
scan := newScanner()
defer freeScanner(scan)
needIndent := false
depth := 0
for _, c := range src {
scan.bytes++
v := scan.step(scan, c)
if v == scanSkipSpace {
continue
}
if v == scanError {
break
}
if needIndent && v != scanEndObject && v != scanEndArray {
needIndent = false
depth++
dst = appendNewline(dst, prefix, indent, depth)
}
// Emit semantically uninteresting bytes
// (in particular, punctuation in strings) unmodified.
if v == scanContinue {
dst = append(dst, c)
continue
}
// Add spacing around real punctuation.
switch c {
case '{', '[':
// delay indent so that empty object and array are formatted as {} and [].
needIndent = true
dst = append(dst, c)
case ',':
dst = append(dst, c)
dst = appendNewline(dst, prefix, indent, depth)
case ':':
dst = append(dst, c, ' ')
case '}', ']':
if needIndent {
// suppress indent in empty object/array
needIndent = false
} else {
depth--
dst = appendNewline(dst, prefix, indent, depth)
}
dst = append(dst, c)
default:
dst = append(dst, c)
}
}
if scan.eof() == scanError {
return dst[:origLen], scan.err
}
return dst, nil
}