prometheus/vendor/github.com/google/go-cmp/cmp/report_compare.go

297 lines
8.9 KiB
Go

// Copyright 2019, The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE.md file.
package cmp
import (
"fmt"
"reflect"
"github.com/google/go-cmp/cmp/internal/value"
)
// TODO: Enforce limits?
// * Enforce maximum number of records to print per node?
// * Enforce maximum size in bytes allowed?
// * As a heuristic, use less verbosity for equal nodes than unequal nodes.
// TODO: Enforce unique outputs?
// * Avoid Stringer methods if it results in same output?
// * Print pointer address if outputs still equal?
// numContextRecords is the number of surrounding equal records to print.
const numContextRecords = 2
type diffMode byte
const (
diffUnknown diffMode = 0
diffIdentical diffMode = ' '
diffRemoved diffMode = '-'
diffInserted diffMode = '+'
)
type typeMode int
const (
// emitType always prints the type.
emitType typeMode = iota
// elideType never prints the type.
elideType
// autoType prints the type only for composite kinds
// (i.e., structs, slices, arrays, and maps).
autoType
)
type formatOptions struct {
// DiffMode controls the output mode of FormatDiff.
//
// If diffUnknown, then produce a diff of the x and y values.
// If diffIdentical, then emit values as if they were equal.
// If diffRemoved, then only emit x values (ignoring y values).
// If diffInserted, then only emit y values (ignoring x values).
DiffMode diffMode
// TypeMode controls whether to print the type for the current node.
//
// As a general rule of thumb, we always print the type of the next node
// after an interface, and always elide the type of the next node after
// a slice or map node.
TypeMode typeMode
// formatValueOptions are options specific to printing reflect.Values.
formatValueOptions
}
func (opts formatOptions) WithDiffMode(d diffMode) formatOptions {
opts.DiffMode = d
return opts
}
func (opts formatOptions) WithTypeMode(t typeMode) formatOptions {
opts.TypeMode = t
return opts
}
// FormatDiff converts a valueNode tree into a textNode tree, where the later
// is a textual representation of the differences detected in the former.
func (opts formatOptions) FormatDiff(v *valueNode) textNode {
// Check whether we have specialized formatting for this node.
// This is not necessary, but helpful for producing more readable outputs.
if opts.CanFormatDiffSlice(v) {
return opts.FormatDiffSlice(v)
}
// For leaf nodes, format the value based on the reflect.Values alone.
if v.MaxDepth == 0 {
switch opts.DiffMode {
case diffUnknown, diffIdentical:
// Format Equal.
if v.NumDiff == 0 {
outx := opts.FormatValue(v.ValueX, visitedPointers{})
outy := opts.FormatValue(v.ValueY, visitedPointers{})
if v.NumIgnored > 0 && v.NumSame == 0 {
return textEllipsis
} else if outx.Len() < outy.Len() {
return outx
} else {
return outy
}
}
// Format unequal.
assert(opts.DiffMode == diffUnknown)
var list textList
outx := opts.WithTypeMode(elideType).FormatValue(v.ValueX, visitedPointers{})
outy := opts.WithTypeMode(elideType).FormatValue(v.ValueY, visitedPointers{})
if outx != nil {
list = append(list, textRecord{Diff: '-', Value: outx})
}
if outy != nil {
list = append(list, textRecord{Diff: '+', Value: outy})
}
return opts.WithTypeMode(emitType).FormatType(v.Type, list)
case diffRemoved:
return opts.FormatValue(v.ValueX, visitedPointers{})
case diffInserted:
return opts.FormatValue(v.ValueY, visitedPointers{})
default:
panic("invalid diff mode")
}
}
// Descend into the child value node.
if v.TransformerName != "" {
out := opts.WithTypeMode(emitType).FormatDiff(v.Value)
out = textWrap{"Inverse(" + v.TransformerName + ", ", out, ")"}
return opts.FormatType(v.Type, out)
} else {
switch k := v.Type.Kind(); k {
case reflect.Struct, reflect.Array, reflect.Slice, reflect.Map:
return opts.FormatType(v.Type, opts.formatDiffList(v.Records, k))
case reflect.Ptr:
return textWrap{"&", opts.FormatDiff(v.Value), ""}
case reflect.Interface:
return opts.WithTypeMode(emitType).FormatDiff(v.Value)
default:
panic(fmt.Sprintf("%v cannot have children", k))
}
}
}
func (opts formatOptions) formatDiffList(recs []reportRecord, k reflect.Kind) textNode {
// Derive record name based on the data structure kind.
var name string
var formatKey func(reflect.Value) string
switch k {
case reflect.Struct:
name = "field"
opts = opts.WithTypeMode(autoType)
formatKey = func(v reflect.Value) string { return v.String() }
case reflect.Slice, reflect.Array:
name = "element"
opts = opts.WithTypeMode(elideType)
formatKey = func(reflect.Value) string { return "" }
case reflect.Map:
name = "entry"
opts = opts.WithTypeMode(elideType)
formatKey = formatMapKey
}
// Handle unification.
switch opts.DiffMode {
case diffIdentical, diffRemoved, diffInserted:
var list textList
var deferredEllipsis bool // Add final "..." to indicate records were dropped
for _, r := range recs {
// Elide struct fields that are zero value.
if k == reflect.Struct {
var isZero bool
switch opts.DiffMode {
case diffIdentical:
isZero = value.IsZero(r.Value.ValueX) || value.IsZero(r.Value.ValueX)
case diffRemoved:
isZero = value.IsZero(r.Value.ValueX)
case diffInserted:
isZero = value.IsZero(r.Value.ValueY)
}
if isZero {
continue
}
}
// Elide ignored nodes.
if r.Value.NumIgnored > 0 && r.Value.NumSame+r.Value.NumDiff == 0 {
deferredEllipsis = !(k == reflect.Slice || k == reflect.Array)
if !deferredEllipsis {
list.AppendEllipsis(diffStats{})
}
continue
}
if out := opts.FormatDiff(r.Value); out != nil {
list = append(list, textRecord{Key: formatKey(r.Key), Value: out})
}
}
if deferredEllipsis {
list.AppendEllipsis(diffStats{})
}
return textWrap{"{", list, "}"}
case diffUnknown:
default:
panic("invalid diff mode")
}
// Handle differencing.
var list textList
groups := coalesceAdjacentRecords(name, recs)
for i, ds := range groups {
// Handle equal records.
if ds.NumDiff() == 0 {
// Compute the number of leading and trailing records to print.
var numLo, numHi int
numEqual := ds.NumIgnored + ds.NumIdentical
for numLo < numContextRecords && numLo+numHi < numEqual && i != 0 {
if r := recs[numLo].Value; r.NumIgnored > 0 && r.NumSame+r.NumDiff == 0 {
break
}
numLo++
}
for numHi < numContextRecords && numLo+numHi < numEqual && i != len(groups)-1 {
if r := recs[numEqual-numHi-1].Value; r.NumIgnored > 0 && r.NumSame+r.NumDiff == 0 {
break
}
numHi++
}
if numEqual-(numLo+numHi) == 1 && ds.NumIgnored == 0 {
numHi++ // Avoid pointless coalescing of a single equal record
}
// Format the equal values.
for _, r := range recs[:numLo] {
out := opts.WithDiffMode(diffIdentical).FormatDiff(r.Value)
list = append(list, textRecord{Key: formatKey(r.Key), Value: out})
}
if numEqual > numLo+numHi {
ds.NumIdentical -= numLo + numHi
list.AppendEllipsis(ds)
}
for _, r := range recs[numEqual-numHi : numEqual] {
out := opts.WithDiffMode(diffIdentical).FormatDiff(r.Value)
list = append(list, textRecord{Key: formatKey(r.Key), Value: out})
}
recs = recs[numEqual:]
continue
}
// Handle unequal records.
for _, r := range recs[:ds.NumDiff()] {
switch {
case opts.CanFormatDiffSlice(r.Value):
out := opts.FormatDiffSlice(r.Value)
list = append(list, textRecord{Key: formatKey(r.Key), Value: out})
case r.Value.NumChildren == r.Value.MaxDepth:
outx := opts.WithDiffMode(diffRemoved).FormatDiff(r.Value)
outy := opts.WithDiffMode(diffInserted).FormatDiff(r.Value)
if outx != nil {
list = append(list, textRecord{Diff: diffRemoved, Key: formatKey(r.Key), Value: outx})
}
if outy != nil {
list = append(list, textRecord{Diff: diffInserted, Key: formatKey(r.Key), Value: outy})
}
default:
out := opts.FormatDiff(r.Value)
list = append(list, textRecord{Key: formatKey(r.Key), Value: out})
}
}
recs = recs[ds.NumDiff():]
}
assert(len(recs) == 0)
return textWrap{"{", list, "}"}
}
// coalesceAdjacentRecords coalesces the list of records into groups of
// adjacent equal, or unequal counts.
func coalesceAdjacentRecords(name string, recs []reportRecord) (groups []diffStats) {
var prevCase int // Arbitrary index into which case last occurred
lastStats := func(i int) *diffStats {
if prevCase != i {
groups = append(groups, diffStats{Name: name})
prevCase = i
}
return &groups[len(groups)-1]
}
for _, r := range recs {
switch rv := r.Value; {
case rv.NumIgnored > 0 && rv.NumSame+rv.NumDiff == 0:
lastStats(1).NumIgnored++
case rv.NumDiff == 0:
lastStats(1).NumIdentical++
case rv.NumDiff > 0 && !rv.ValueY.IsValid():
lastStats(2).NumRemoved++
case rv.NumDiff > 0 && !rv.ValueX.IsValid():
lastStats(2).NumInserted++
default:
lastStats(2).NumModified++
}
}
return groups
}