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go-discogs/vendor/github.com/google/go-cmp/cmp/report_slices.go

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// 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 file.
package cmp
import (
"bytes"
"fmt"
"reflect"
"strconv"
"strings"
"unicode"
"unicode/utf8"
"github.com/google/go-cmp/cmp/internal/diff"
)
// CanFormatDiffSlice reports whether we support custom formatting for nodes
// that are slices of primitive kinds or strings.
func (opts formatOptions) CanFormatDiffSlice(v *valueNode) bool {
switch {
case opts.DiffMode != diffUnknown:
return false // Must be formatting in diff mode
case v.NumDiff == 0:
return false // No differences detected
case !v.ValueX.IsValid() || !v.ValueY.IsValid():
return false // Both values must be valid
case v.Type.Kind() == reflect.Slice && (v.ValueX.Len() == 0 || v.ValueY.Len() == 0):
return false // Both slice values have to be non-empty
case v.NumIgnored > 0:
return false // Some ignore option was used
case v.NumTransformed > 0:
return false // Some transform option was used
case v.NumCompared > 1:
return false // More than one comparison was used
case v.NumCompared == 1 && v.Type.Name() != "":
// The need for cmp to check applicability of options on every element
// in a slice is a significant performance detriment for large []byte.
// The workaround is to specify Comparer(bytes.Equal),
// which enables cmp to compare []byte more efficiently.
// If they differ, we still want to provide batched diffing.
// The logic disallows named types since they tend to have their own
// String method, with nicer formatting than what this provides.
return false
}
switch t := v.Type; t.Kind() {
case reflect.String:
case reflect.Array, reflect.Slice:
// Only slices of primitive types have specialized handling.
switch t.Elem().Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr,
reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
default:
return false
}
// If a sufficient number of elements already differ,
// use specialized formatting even if length requirement is not met.
if v.NumDiff > v.NumSame {
return true
}
default:
return false
}
// Use specialized string diffing for longer slices or strings.
const minLength = 64
return v.ValueX.Len() >= minLength && v.ValueY.Len() >= minLength
}
// FormatDiffSlice prints a diff for the slices (or strings) represented by v.
// This provides custom-tailored logic to make printing of differences in
// textual strings and slices of primitive kinds more readable.
func (opts formatOptions) FormatDiffSlice(v *valueNode) textNode {
assert(opts.DiffMode == diffUnknown)
t, vx, vy := v.Type, v.ValueX, v.ValueY
// Auto-detect the type of the data.
var isLinedText, isText, isBinary bool
var sx, sy string
switch {
case t.Kind() == reflect.String:
sx, sy = vx.String(), vy.String()
isText = true // Initial estimate, verify later
case t.Kind() == reflect.Slice && t.Elem() == reflect.TypeOf(byte(0)):
sx, sy = string(vx.Bytes()), string(vy.Bytes())
isBinary = true // Initial estimate, verify later
case t.Kind() == reflect.Array:
// Arrays need to be addressable for slice operations to work.
vx2, vy2 := reflect.New(t).Elem(), reflect.New(t).Elem()
vx2.Set(vx)
vy2.Set(vy)
vx, vy = vx2, vy2
}
if isText || isBinary {
var numLines, lastLineIdx, maxLineLen int
isBinary = !utf8.ValidString(sx) || !utf8.ValidString(sy)
for i, r := range sx + sy {
if !(unicode.IsPrint(r) || unicode.IsSpace(r)) || r == utf8.RuneError {
isBinary = true
break
}
if r == '\n' {
if maxLineLen < i-lastLineIdx {
maxLineLen = i - lastLineIdx
}
lastLineIdx = i + 1
numLines++
}
}
isText = !isBinary
isLinedText = isText && numLines >= 4 && maxLineLen <= 1024
}
// Format the string into printable records.
var list textList
var delim string
switch {
// If the text appears to be multi-lined text,
// then perform differencing across individual lines.
case isLinedText:
ssx := strings.Split(sx, "\n")
ssy := strings.Split(sy, "\n")
list = opts.formatDiffSlice(
reflect.ValueOf(ssx), reflect.ValueOf(ssy), 1, "line",
func(v reflect.Value, d diffMode) textRecord {
s := formatString(v.Index(0).String())
return textRecord{Diff: d, Value: textLine(s)}
},
)
delim = "\n"
// If possible, use a custom triple-quote (""") syntax for printing
// differences in a string literal. This format is more readable,
// but has edge-cases where differences are visually indistinguishable.
// This format is avoided under the following conditions:
// • A line starts with `"""`
// • A line starts with "..."
// • A line contains non-printable characters
// • Adjacent different lines differ only by whitespace
//
// For example:
// """
// ... // 3 identical lines
// foo
// bar
// - baz
// + BAZ
// """
isTripleQuoted := true
prevRemoveLines := map[string]bool{}
prevInsertLines := map[string]bool{}
var list2 textList
list2 = append(list2, textRecord{Value: textLine(`"""`), ElideComma: true})
for _, r := range list {
if !r.Value.Equal(textEllipsis) {
line, _ := strconv.Unquote(string(r.Value.(textLine)))
line = strings.TrimPrefix(strings.TrimSuffix(line, "\r"), "\r") // trim leading/trailing carriage returns for legacy Windows endline support
normLine := strings.Map(func(r rune) rune {
if unicode.IsSpace(r) {
return -1 // drop whitespace to avoid visually indistinguishable output
}
return r
}, line)
isPrintable := func(r rune) bool {
return unicode.IsPrint(r) || r == '\t' // specially treat tab as printable
}
isTripleQuoted = !strings.HasPrefix(line, `"""`) && !strings.HasPrefix(line, "...") && strings.TrimFunc(line, isPrintable) == ""
switch r.Diff {
case diffRemoved:
isTripleQuoted = isTripleQuoted && !prevInsertLines[normLine]
prevRemoveLines[normLine] = true
case diffInserted:
isTripleQuoted = isTripleQuoted && !prevRemoveLines[normLine]
prevInsertLines[normLine] = true
}
if !isTripleQuoted {
break
}
r.Value = textLine(line)
r.ElideComma = true
}
if !(r.Diff == diffRemoved || r.Diff == diffInserted) { // start a new non-adjacent difference group
prevRemoveLines = map[string]bool{}
prevInsertLines = map[string]bool{}
}
list2 = append(list2, r)
}
if r := list2[len(list2)-1]; r.Diff == diffIdentical && len(r.Value.(textLine)) == 0 {
list2 = list2[:len(list2)-1] // elide single empty line at the end
}
list2 = append(list2, textRecord{Value: textLine(`"""`), ElideComma: true})
if isTripleQuoted {
var out textNode = &textWrap{Prefix: "(", Value: list2, Suffix: ")"}
switch t.Kind() {
case reflect.String:
if t != reflect.TypeOf(string("")) {
out = opts.FormatType(t, out)
}
case reflect.Slice:
// Always emit type for slices since the triple-quote syntax
// looks like a string (not a slice).
opts = opts.WithTypeMode(emitType)
out = opts.FormatType(t, out)
}
return out
}
// If the text appears to be single-lined text,
// then perform differencing in approximately fixed-sized chunks.
// The output is printed as quoted strings.
case isText:
list = opts.formatDiffSlice(
reflect.ValueOf(sx), reflect.ValueOf(sy), 64, "byte",
func(v reflect.Value, d diffMode) textRecord {
s := formatString(v.String())
return textRecord{Diff: d, Value: textLine(s)}
},
)
delim = ""
// If the text appears to be binary data,
// then perform differencing in approximately fixed-sized chunks.
// The output is inspired by hexdump.
case isBinary:
list = opts.formatDiffSlice(
reflect.ValueOf(sx), reflect.ValueOf(sy), 16, "byte",
func(v reflect.Value, d diffMode) textRecord {
var ss []string
for i := 0; i < v.Len(); i++ {
ss = append(ss, formatHex(v.Index(i).Uint()))
}
s := strings.Join(ss, ", ")
comment := commentString(fmt.Sprintf("%c|%v|", d, formatASCII(v.String())))
return textRecord{Diff: d, Value: textLine(s), Comment: comment}
},
)
// For all other slices of primitive types,
// then perform differencing in approximately fixed-sized chunks.
// The size of each chunk depends on the width of the element kind.
default:
var chunkSize int
if t.Elem().Kind() == reflect.Bool {
chunkSize = 16
} else {
switch t.Elem().Bits() {
case 8:
chunkSize = 16
case 16:
chunkSize = 12
case 32:
chunkSize = 8
default:
chunkSize = 8
}
}
list = opts.formatDiffSlice(
vx, vy, chunkSize, t.Elem().Kind().String(),
func(v reflect.Value, d diffMode) textRecord {
var ss []string
for i := 0; i < v.Len(); i++ {
switch t.Elem().Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
ss = append(ss, fmt.Sprint(v.Index(i).Int()))
case reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64:
ss = append(ss, fmt.Sprint(v.Index(i).Uint()))
case reflect.Uint8, reflect.Uintptr:
ss = append(ss, formatHex(v.Index(i).Uint()))
case reflect.Bool, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
ss = append(ss, fmt.Sprint(v.Index(i).Interface()))
}
}
s := strings.Join(ss, ", ")
return textRecord{Diff: d, Value: textLine(s)}
},
)
}
// Wrap the output with appropriate type information.
var out textNode = &textWrap{Prefix: "{", Value: list, Suffix: "}"}
if !isText {
// The "{...}" byte-sequence literal is not valid Go syntax for strings.
// Emit the type for extra clarity (e.g. "string{...}").
if t.Kind() == reflect.String {
opts = opts.WithTypeMode(emitType)
}
return opts.FormatType(t, out)
}
switch t.Kind() {
case reflect.String:
out = &textWrap{Prefix: "strings.Join(", Value: out, Suffix: fmt.Sprintf(", %q)", delim)}
if t != reflect.TypeOf(string("")) {
out = opts.FormatType(t, out)
}
case reflect.Slice:
out = &textWrap{Prefix: "bytes.Join(", Value: out, Suffix: fmt.Sprintf(", %q)", delim)}
if t != reflect.TypeOf([]byte(nil)) {
out = opts.FormatType(t, out)
}
}
return out
}
// formatASCII formats s as an ASCII string.
// This is useful for printing binary strings in a semi-legible way.
func formatASCII(s string) string {
b := bytes.Repeat([]byte{'.'}, len(s))
for i := 0; i < len(s); i++ {
if ' ' <= s[i] && s[i] <= '~' {
b[i] = s[i]
}
}
return string(b)
}
func (opts formatOptions) formatDiffSlice(
vx, vy reflect.Value, chunkSize int, name string,
makeRec func(reflect.Value, diffMode) textRecord,
) (list textList) {
es := diff.Difference(vx.Len(), vy.Len(), func(ix int, iy int) diff.Result {
return diff.BoolResult(vx.Index(ix).Interface() == vy.Index(iy).Interface())
})
appendChunks := func(v reflect.Value, d diffMode) int {
n0 := v.Len()
for v.Len() > 0 {
n := chunkSize
if n > v.Len() {
n = v.Len()
}
list = append(list, makeRec(v.Slice(0, n), d))
v = v.Slice(n, v.Len())
}
return n0 - v.Len()
}
var numDiffs int
maxLen := -1
if opts.LimitVerbosity {
maxLen = (1 << opts.verbosity()) << 2 // 4, 8, 16, 32, 64, etc...
opts.VerbosityLevel--
}
groups := coalesceAdjacentEdits(name, es)
groups = coalesceInterveningIdentical(groups, chunkSize/4)
maxGroup := diffStats{Name: name}
for i, ds := range groups {
if maxLen >= 0 && numDiffs >= maxLen {
maxGroup = maxGroup.Append(ds)
continue
}
// Print equal.
if ds.NumDiff() == 0 {
// Compute the number of leading and trailing equal bytes to print.
var numLo, numHi int
numEqual := ds.NumIgnored + ds.NumIdentical
for numLo < chunkSize*numContextRecords && numLo+numHi < numEqual && i != 0 {
numLo++
}
for numHi < chunkSize*numContextRecords && numLo+numHi < numEqual && i != len(groups)-1 {
numHi++
}
if numEqual-(numLo+numHi) <= chunkSize && ds.NumIgnored == 0 {
numHi = numEqual - numLo // Avoid pointless coalescing of single equal row
}
// Print the equal bytes.
appendChunks(vx.Slice(0, numLo), diffIdentical)
if numEqual > numLo+numHi {
ds.NumIdentical -= numLo + numHi
list.AppendEllipsis(ds)
}
appendChunks(vx.Slice(numEqual-numHi, numEqual), diffIdentical)
vx = vx.Slice(numEqual, vx.Len())
vy = vy.Slice(numEqual, vy.Len())
continue
}
// Print unequal.
len0 := len(list)
nx := appendChunks(vx.Slice(0, ds.NumIdentical+ds.NumRemoved+ds.NumModified), diffRemoved)
vx = vx.Slice(nx, vx.Len())
ny := appendChunks(vy.Slice(0, ds.NumIdentical+ds.NumInserted+ds.NumModified), diffInserted)
vy = vy.Slice(ny, vy.Len())
numDiffs += len(list) - len0
}
if maxGroup.IsZero() {
assert(vx.Len() == 0 && vy.Len() == 0)
} else {
list.AppendEllipsis(maxGroup)
}
return list
}
// coalesceAdjacentEdits coalesces the list of edits into groups of adjacent
// equal or unequal counts.
func coalesceAdjacentEdits(name string, es diff.EditScript) (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 _, e := range es {
switch e {
case diff.Identity:
lastStats(1).NumIdentical++
case diff.UniqueX:
lastStats(2).NumRemoved++
case diff.UniqueY:
lastStats(2).NumInserted++
case diff.Modified:
lastStats(2).NumModified++
}
}
return groups
}
// coalesceInterveningIdentical coalesces sufficiently short (<= windowSize)
// equal groups into adjacent unequal groups that currently result in a
// dual inserted/removed printout. This acts as a high-pass filter to smooth
// out high-frequency changes within the windowSize.
func coalesceInterveningIdentical(groups []diffStats, windowSize int) []diffStats {
groups, groupsOrig := groups[:0], groups
for i, ds := range groupsOrig {
if len(groups) >= 2 && ds.NumDiff() > 0 {
prev := &groups[len(groups)-2] // Unequal group
curr := &groups[len(groups)-1] // Equal group
next := &groupsOrig[i] // Unequal group
hadX, hadY := prev.NumRemoved > 0, prev.NumInserted > 0
hasX, hasY := next.NumRemoved > 0, next.NumInserted > 0
if ((hadX || hasX) && (hadY || hasY)) && curr.NumIdentical <= windowSize {
*prev = prev.Append(*curr).Append(*next)
groups = groups[:len(groups)-1] // Truncate off equal group
continue
}
}
groups = append(groups, ds)
}
return groups
}