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