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			302 lines
		
	
	
		
			9.1 KiB
		
	
	
	
		
			Go
		
	
	
	
	
	
			
		
		
	
	
			302 lines
		
	
	
		
			9.1 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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	var withinSlice bool
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	if v.parent != nil && (v.parent.Type.Kind() == reflect.Slice || v.parent.Type.Kind() == reflect.Array) {
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		withinSlice = true
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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, withinSlice, visitedPointers{})
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				outy := opts.FormatValue(v.ValueY, withinSlice, 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, withinSlice, visitedPointers{})
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			outy := opts.WithTypeMode(elideType).FormatValue(v.ValueY, withinSlice, 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, withinSlice, visitedPointers{})
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		case diffInserted:
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			return opts.FormatValue(v.ValueY, withinSlice, 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.ValueY)
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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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