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