329 lines
7.1 KiB
Go
329 lines
7.1 KiB
Go
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package pretty
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import (
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"fmt"
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"io"
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"reflect"
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"strconv"
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"text/tabwriter"
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"github.com/kr/text"
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)
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type formatter struct {
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v reflect.Value
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force bool
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quote bool
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}
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// Formatter makes a wrapper, f, that will format x as go source with line
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// breaks and tabs. Object f responds to the "%v" formatting verb when both the
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// "#" and " " (space) flags are set, for example:
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//
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// fmt.Sprintf("%# v", Formatter(x))
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//
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// If one of these two flags is not set, or any other verb is used, f will
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// format x according to the usual rules of package fmt.
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// In particular, if x satisfies fmt.Formatter, then x.Format will be called.
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func Formatter(x interface{}) (f fmt.Formatter) {
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return formatter{v: reflect.ValueOf(x), quote: true}
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}
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func (fo formatter) String() string {
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return fmt.Sprint(fo.v.Interface()) // unwrap it
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}
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func (fo formatter) passThrough(f fmt.State, c rune) {
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s := "%"
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for i := 0; i < 128; i++ {
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if f.Flag(i) {
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s += string(i)
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}
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}
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if w, ok := f.Width(); ok {
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s += fmt.Sprintf("%d", w)
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}
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if p, ok := f.Precision(); ok {
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s += fmt.Sprintf(".%d", p)
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}
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s += string(c)
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fmt.Fprintf(f, s, fo.v.Interface())
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}
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func (fo formatter) Format(f fmt.State, c rune) {
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if fo.force || c == 'v' && f.Flag('#') && f.Flag(' ') {
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w := tabwriter.NewWriter(f, 4, 4, 1, ' ', 0)
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p := &printer{tw: w, Writer: w, visited: make(map[visit]int)}
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p.printValue(fo.v, true, fo.quote)
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w.Flush()
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return
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}
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fo.passThrough(f, c)
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}
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type printer struct {
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io.Writer
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tw *tabwriter.Writer
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visited map[visit]int
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depth int
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}
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func (p *printer) indent() *printer {
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q := *p
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q.tw = tabwriter.NewWriter(p.Writer, 4, 4, 1, ' ', 0)
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q.Writer = text.NewIndentWriter(q.tw, []byte{'\t'})
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return &q
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}
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func (p *printer) printInline(v reflect.Value, x interface{}, showType bool) {
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if showType {
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io.WriteString(p, v.Type().String())
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fmt.Fprintf(p, "(%#v)", x)
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} else {
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fmt.Fprintf(p, "%#v", x)
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}
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}
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// printValue must keep track of already-printed pointer values to avoid
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// infinite recursion.
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type visit struct {
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v uintptr
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typ reflect.Type
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}
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func (p *printer) printValue(v reflect.Value, showType, quote bool) {
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if p.depth > 10 {
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io.WriteString(p, "!%v(DEPTH EXCEEDED)")
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return
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}
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switch v.Kind() {
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case reflect.Bool:
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p.printInline(v, v.Bool(), showType)
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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p.printInline(v, v.Int(), showType)
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
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p.printInline(v, v.Uint(), showType)
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case reflect.Float32, reflect.Float64:
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p.printInline(v, v.Float(), showType)
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case reflect.Complex64, reflect.Complex128:
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fmt.Fprintf(p, "%#v", v.Complex())
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case reflect.String:
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p.fmtString(v.String(), quote)
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case reflect.Map:
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t := v.Type()
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if showType {
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io.WriteString(p, t.String())
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}
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writeByte(p, '{')
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if nonzero(v) {
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expand := !canInline(v.Type())
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pp := p
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if expand {
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writeByte(p, '\n')
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pp = p.indent()
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}
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keys := v.MapKeys()
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for i := 0; i < v.Len(); i++ {
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showTypeInStruct := true
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k := keys[i]
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mv := v.MapIndex(k)
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pp.printValue(k, false, true)
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writeByte(pp, ':')
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if expand {
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writeByte(pp, '\t')
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}
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showTypeInStruct = t.Elem().Kind() == reflect.Interface
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pp.printValue(mv, showTypeInStruct, true)
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if expand {
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io.WriteString(pp, ",\n")
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} else if i < v.Len()-1 {
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io.WriteString(pp, ", ")
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}
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}
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if expand {
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pp.tw.Flush()
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}
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}
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writeByte(p, '}')
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case reflect.Struct:
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t := v.Type()
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if v.CanAddr() {
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addr := v.UnsafeAddr()
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vis := visit{addr, t}
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if vd, ok := p.visited[vis]; ok && vd < p.depth {
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p.fmtString(t.String()+"{(CYCLIC REFERENCE)}", false)
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break // don't print v again
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}
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p.visited[vis] = p.depth
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}
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if showType {
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io.WriteString(p, t.String())
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}
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writeByte(p, '{')
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if nonzero(v) {
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expand := !canInline(v.Type())
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pp := p
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if expand {
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writeByte(p, '\n')
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pp = p.indent()
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}
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for i := 0; i < v.NumField(); i++ {
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showTypeInStruct := true
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if f := t.Field(i); f.Name != "" {
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io.WriteString(pp, f.Name)
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writeByte(pp, ':')
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if expand {
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writeByte(pp, '\t')
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}
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showTypeInStruct = labelType(f.Type)
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}
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pp.printValue(getField(v, i), showTypeInStruct, true)
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if expand {
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io.WriteString(pp, ",\n")
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} else if i < v.NumField()-1 {
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io.WriteString(pp, ", ")
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}
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}
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if expand {
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pp.tw.Flush()
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}
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}
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writeByte(p, '}')
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case reflect.Interface:
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switch e := v.Elem(); {
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case e.Kind() == reflect.Invalid:
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io.WriteString(p, "nil")
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case e.IsValid():
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pp := *p
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pp.depth++
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pp.printValue(e, showType, true)
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default:
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io.WriteString(p, v.Type().String())
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io.WriteString(p, "(nil)")
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}
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case reflect.Array, reflect.Slice:
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t := v.Type()
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if showType {
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io.WriteString(p, t.String())
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}
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if v.Kind() == reflect.Slice && v.IsNil() && showType {
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io.WriteString(p, "(nil)")
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break
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}
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if v.Kind() == reflect.Slice && v.IsNil() {
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io.WriteString(p, "nil")
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break
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}
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writeByte(p, '{')
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expand := !canInline(v.Type())
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pp := p
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if expand {
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writeByte(p, '\n')
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pp = p.indent()
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}
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for i := 0; i < v.Len(); i++ {
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showTypeInSlice := t.Elem().Kind() == reflect.Interface
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pp.printValue(v.Index(i), showTypeInSlice, true)
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if expand {
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io.WriteString(pp, ",\n")
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} else if i < v.Len()-1 {
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io.WriteString(pp, ", ")
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}
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}
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if expand {
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pp.tw.Flush()
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}
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writeByte(p, '}')
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case reflect.Ptr:
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e := v.Elem()
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if !e.IsValid() {
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writeByte(p, '(')
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io.WriteString(p, v.Type().String())
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io.WriteString(p, ")(nil)")
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} else {
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pp := *p
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pp.depth++
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writeByte(pp, '&')
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pp.printValue(e, true, true)
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}
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case reflect.Chan:
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x := v.Pointer()
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if showType {
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writeByte(p, '(')
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io.WriteString(p, v.Type().String())
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fmt.Fprintf(p, ")(%#v)", x)
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} else {
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fmt.Fprintf(p, "%#v", x)
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}
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case reflect.Func:
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io.WriteString(p, v.Type().String())
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io.WriteString(p, " {...}")
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case reflect.UnsafePointer:
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p.printInline(v, v.Pointer(), showType)
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case reflect.Invalid:
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io.WriteString(p, "nil")
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}
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}
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func canInline(t reflect.Type) bool {
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switch t.Kind() {
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case reflect.Map:
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return !canExpand(t.Elem())
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case reflect.Struct:
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for i := 0; i < t.NumField(); i++ {
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if canExpand(t.Field(i).Type) {
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return false
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}
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}
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return true
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case reflect.Interface:
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return false
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case reflect.Array, reflect.Slice:
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return !canExpand(t.Elem())
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case reflect.Ptr:
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return false
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case reflect.Chan, reflect.Func, reflect.UnsafePointer:
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return false
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}
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return true
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}
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func canExpand(t reflect.Type) bool {
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switch t.Kind() {
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case reflect.Map, reflect.Struct,
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reflect.Interface, reflect.Array, reflect.Slice,
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reflect.Ptr:
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return true
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}
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return false
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}
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func labelType(t reflect.Type) bool {
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switch t.Kind() {
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case reflect.Interface, reflect.Struct:
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return true
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}
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return false
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}
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func (p *printer) fmtString(s string, quote bool) {
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if quote {
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s = strconv.Quote(s)
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}
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io.WriteString(p, s)
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}
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func writeByte(w io.Writer, b byte) {
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w.Write([]byte{b})
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}
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func getField(v reflect.Value, i int) reflect.Value {
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val := v.Field(i)
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if val.Kind() == reflect.Interface && !val.IsNil() {
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val = val.Elem()
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}
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return val
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}
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