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// Copyright 2016 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package pretty implements a simple pretty-printer. It is intended for
// debugging the output of tests.
//
// It follows pointers and produces multi-line output for complex values like
// slices, maps and structs.
package pretty
import (
"fmt"
"io"
"reflect"
"sort"
"strings"
"time"
)
// Indent is the string output at each level of indentation.
var Indent = " "
// Value returns a value that will print prettily when used as an
// argument for the %v or %s format specifiers.
// With no flags, struct fields and map keys with default values are omitted.
// With the '+' or '#' flags, all values are displayed.
//
// This package does not detect cycles. Attempting to print a Value that
// contains cycles will result in unbounded recursion.
func Value(v interface{}) val { return val{v: v} }
// val is a value.
type val struct{ v interface{} }
// Format implements the fmt.Formatter interface.
func (v val) Format(s fmt.State, c rune) {
if c == 'v' || c == 's' {
fprint(s, reflect.ValueOf(v.v), state{
defaults: s.Flag('+') || s.Flag('#'),
})
} else {
fmt.Fprintf(s, "%%!%c(pretty.val)", c)
}
}
type state struct {
level int
prefix, suffix string
defaults bool
}
const maxLevel = 100
var typeOfTime = reflect.TypeOf(time.Time{})
func fprint(w io.Writer, v reflect.Value, s state) {
if s.level > maxLevel {
fmt.Fprintln(w, "pretty: max nested depth exceeded")
return
}
indent := strings.Repeat(Indent, s.level)
fmt.Fprintf(w, "%s%s", indent, s.prefix)
if isNil(v) {
fmt.Fprintf(w, "nil%s", s.suffix)
return
}
if v.Type().Kind() == reflect.Interface {
v = v.Elem()
}
if v.Type() == typeOfTime {
fmt.Fprintf(w, "%s%s", v.Interface(), s.suffix)
return
}
for v.Type().Kind() == reflect.Ptr {
fmt.Fprintf(w, "&")
v = v.Elem()
}
switch v.Type().Kind() {
default:
fmt.Fprintf(w, "%s%s", short(v), s.suffix)
case reflect.Array:
fmt.Fprintf(w, "%s{\n", v.Type())
for i := 0; i < v.Len(); i++ {
fprint(w, v.Index(i), state{
level: s.level + 1,
prefix: "",
suffix: ",",
defaults: s.defaults,
})
fmt.Fprintln(w)
}
fmt.Fprintf(w, "%s}", indent)
case reflect.Slice:
fmt.Fprintf(w, "%s{", v.Type())
if v.Len() > 0 {
fmt.Fprintln(w)
for i := 0; i < v.Len(); i++ {
fprint(w, v.Index(i), state{
level: s.level + 1,
prefix: "",
suffix: ",",
defaults: s.defaults,
})
fmt.Fprintln(w)
}
}
fmt.Fprintf(w, "%s}%s", indent, s.suffix)
case reflect.Map:
fmt.Fprintf(w, "%s{", v.Type())
if v.Len() > 0 {
fmt.Fprintln(w)
keys := v.MapKeys()
maybeSort(keys, v.Type().Key())
for _, key := range keys {
val := v.MapIndex(key)
if s.defaults || !isDefault(val) {
fprint(w, val, state{
level: s.level + 1,
prefix: short(key) + ": ",
suffix: ",",
defaults: s.defaults,
})
fmt.Fprintln(w)
}
}
}
fmt.Fprintf(w, "%s}%s", indent, s.suffix)
case reflect.Struct:
t := v.Type()
fmt.Fprintf(w, "%s{\n", t)
for i := 0; i < t.NumField(); i++ {
f := v.Field(i)
if s.defaults || !isDefault(f) {
fprint(w, f, state{
level: s.level + 1,
prefix: t.Field(i).Name + ": ",
suffix: ",",
defaults: s.defaults,
})
fmt.Fprintln(w)
}
}
fmt.Fprintf(w, "%s}%s", indent, s.suffix)
}
}
func isNil(v reflect.Value) bool {
if !v.IsValid() {
return true
}
switch v.Type().Kind() {
case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
return v.IsNil()
default:
return false
}
}
func isDefault(v reflect.Value) bool {
if !v.IsValid() {
return true
}
t := v.Type()
switch t.Kind() {
case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
return v.IsNil()
default:
if !v.CanInterface() {
return false
}
return t.Comparable() && v.Interface() == reflect.Zero(t).Interface()
}
}
// short returns a short, one-line string for v.
func short(v reflect.Value) string {
if !v.IsValid() {
return "nil"
}
if v.Type().Kind() == reflect.String {
return fmt.Sprintf("%q", v)
}
return fmt.Sprintf("%v", v)
}
func maybeSort(vs []reflect.Value, t reflect.Type) {
if less := lessFunc(t); less != nil {
sort.Sort(&sorter{vs, less})
}
}
// lessFunc returns a function that implements the "<" operator
// for the given type, or nil if the type doesn't support "<" .
func lessFunc(t reflect.Type) func(v1, v2 interface{}) bool {
switch t.Kind() {
case reflect.String:
return func(v1, v2 interface{}) bool { return v1.(string) < v2.(string) }
case reflect.Int:
return func(v1, v2 interface{}) bool { return v1.(int) < v2.(int) }
case reflect.Int8:
return func(v1, v2 interface{}) bool { return v1.(int8) < v2.(int8) }
case reflect.Int16:
return func(v1, v2 interface{}) bool { return v1.(int16) < v2.(int16) }
case reflect.Int32:
return func(v1, v2 interface{}) bool { return v1.(int32) < v2.(int32) }
case reflect.Int64:
return func(v1, v2 interface{}) bool { return v1.(int64) < v2.(int64) }
case reflect.Uint:
return func(v1, v2 interface{}) bool { return v1.(uint) < v2.(uint) }
case reflect.Uint8:
return func(v1, v2 interface{}) bool { return v1.(uint8) < v2.(uint8) }
case reflect.Uint16:
return func(v1, v2 interface{}) bool { return v1.(uint16) < v2.(uint16) }
case reflect.Uint32:
return func(v1, v2 interface{}) bool { return v1.(uint32) < v2.(uint32) }
case reflect.Uint64:
return func(v1, v2 interface{}) bool { return v1.(uint64) < v2.(uint64) }
case reflect.Float32:
return func(v1, v2 interface{}) bool { return v1.(float32) < v2.(float32) }
case reflect.Float64:
return func(v1, v2 interface{}) bool { return v1.(float64) < v2.(float64) }
default:
return nil
}
}
type sorter struct {
vs []reflect.Value
less func(v1, v2 interface{}) bool
}
func (s *sorter) Len() int { return len(s.vs) }
func (s *sorter) Swap(i, j int) { s.vs[i], s.vs[j] = s.vs[j], s.vs[i] }
func (s *sorter) Less(i, j int) bool { return s.less(s.vs[i].Interface(), s.vs[j].Interface()) }