353 lines
8.1 KiB
Go
353 lines
8.1 KiB
Go
// Package deep provides function deep.Equal which is like reflect.DeepEqual but
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// returns a list of differences. This is helpful when comparing complex types
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// like structures and maps.
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package deep
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import (
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"errors"
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"fmt"
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"log"
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"reflect"
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"strings"
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)
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var (
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// FloatPrecision is the number of decimal places to round float values
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// to when comparing.
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FloatPrecision = 10
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// MaxDiff specifies the maximum number of differences to return.
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MaxDiff = 10
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// MaxDepth specifies the maximum levels of a struct to recurse into.
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MaxDepth = 10
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// LogErrors causes errors to be logged to STDERR when true.
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LogErrors = false
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// CompareUnexportedFields causes unexported struct fields, like s in
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// T{s int}, to be comparsed when true.
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CompareUnexportedFields = false
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)
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var (
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// ErrMaxRecursion is logged when MaxDepth is reached.
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ErrMaxRecursion = errors.New("recursed to MaxDepth")
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// ErrTypeMismatch is logged when Equal passed two different types of values.
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ErrTypeMismatch = errors.New("variables are different reflect.Type")
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// ErrNotHandled is logged when a primitive Go kind is not handled.
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ErrNotHandled = errors.New("cannot compare the reflect.Kind")
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)
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type cmp struct {
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diff []string
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buff []string
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floatFormat string
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}
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var errorType = reflect.TypeOf((*error)(nil)).Elem()
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// Equal compares variables a and b, recursing into their structure up to
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// MaxDepth levels deep, and returns a list of differences, or nil if there are
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// none. Some differences may not be found if an error is also returned.
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//
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// If a type has an Equal method, like time.Equal, it is called to check for
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// equality.
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func Equal(a, b interface{}) []string {
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aVal := reflect.ValueOf(a)
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bVal := reflect.ValueOf(b)
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c := &cmp{
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diff: []string{},
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buff: []string{},
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floatFormat: fmt.Sprintf("%%.%df", FloatPrecision),
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}
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if a == nil && b == nil {
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return nil
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} else if a == nil && b != nil {
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c.saveDiff(b, "<nil pointer>")
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} else if a != nil && b == nil {
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c.saveDiff(a, "<nil pointer>")
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}
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if len(c.diff) > 0 {
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return c.diff
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}
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c.equals(aVal, bVal, 0)
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if len(c.diff) > 0 {
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return c.diff // diffs
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}
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return nil // no diffs
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}
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func (c *cmp) equals(a, b reflect.Value, level int) {
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if level > MaxDepth {
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logError(ErrMaxRecursion)
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return
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}
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// Check if one value is nil, e.g. T{x: *X} and T.x is nil
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if !a.IsValid() || !b.IsValid() {
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if a.IsValid() && !b.IsValid() {
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c.saveDiff(a.Type(), "<nil pointer>")
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} else if !a.IsValid() && b.IsValid() {
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c.saveDiff("<nil pointer>", b.Type())
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}
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return
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}
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// If differenet types, they can't be equal
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aType := a.Type()
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bType := b.Type()
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if aType != bType {
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c.saveDiff(aType, bType)
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logError(ErrTypeMismatch)
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return
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}
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// Primitive https://golang.org/pkg/reflect/#Kind
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aKind := a.Kind()
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bKind := b.Kind()
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// If both types implement the error interface, compare the error strings.
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// This must be done before dereferencing because the interface is on a
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// pointer receiver.
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if aType.Implements(errorType) && bType.Implements(errorType) {
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if a.Elem().IsValid() && b.Elem().IsValid() { // both err != nil
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aString := a.MethodByName("Error").Call(nil)[0].String()
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bString := b.MethodByName("Error").Call(nil)[0].String()
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if aString != bString {
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c.saveDiff(aString, bString)
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}
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return
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}
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}
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// Dereference pointers and interface{}
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if aElem, bElem := (aKind == reflect.Ptr || aKind == reflect.Interface),
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(bKind == reflect.Ptr || bKind == reflect.Interface); aElem || bElem {
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if aElem {
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a = a.Elem()
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}
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if bElem {
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b = b.Elem()
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}
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c.equals(a, b, level+1)
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return
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}
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// Types with an Equal(), like time.Time.
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eqFunc := a.MethodByName("Equal")
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if eqFunc.IsValid() {
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retVals := eqFunc.Call([]reflect.Value{b})
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if !retVals[0].Bool() {
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c.saveDiff(a, b)
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}
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return
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}
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switch aKind {
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/////////////////////////////////////////////////////////////////////
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// Iterable kinds
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/////////////////////////////////////////////////////////////////////
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case reflect.Struct:
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/*
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The variables are structs like:
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type T struct {
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FirstName string
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LastName string
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}
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Type = <pkg>.T, Kind = reflect.Struct
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Iterate through the fields (FirstName, LastName), recurse into their values.
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*/
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for i := 0; i < a.NumField(); i++ {
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if aType.Field(i).PkgPath != "" && !CompareUnexportedFields {
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continue // skip unexported field, e.g. s in type T struct {s string}
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}
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c.push(aType.Field(i).Name) // push field name to buff
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// Get the Value for each field, e.g. FirstName has Type = string,
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// Kind = reflect.String.
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af := a.Field(i)
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bf := b.Field(i)
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// Recurse to compare the field values
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c.equals(af, bf, level+1)
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c.pop() // pop field name from buff
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if len(c.diff) >= MaxDiff {
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break
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}
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}
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case reflect.Map:
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/*
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The variables are maps like:
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map[string]int{
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"foo": 1,
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"bar": 2,
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}
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Type = map[string]int, Kind = reflect.Map
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Or:
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type T map[string]int{}
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Type = <pkg>.T, Kind = reflect.Map
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Iterate through the map keys (foo, bar), recurse into their values.
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*/
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if a.IsNil() || b.IsNil() {
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if a.IsNil() && !b.IsNil() {
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c.saveDiff("<nil map>", b)
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} else if !a.IsNil() && b.IsNil() {
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c.saveDiff(a, "<nil map>")
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}
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return
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}
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if a.Pointer() == b.Pointer() {
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return
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}
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for _, key := range a.MapKeys() {
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c.push(fmt.Sprintf("map[%s]", key))
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aVal := a.MapIndex(key)
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bVal := b.MapIndex(key)
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if bVal.IsValid() {
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c.equals(aVal, bVal, level+1)
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} else {
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c.saveDiff(aVal, "<does not have key>")
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}
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c.pop()
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if len(c.diff) >= MaxDiff {
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return
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}
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}
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for _, key := range b.MapKeys() {
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if aVal := a.MapIndex(key); aVal.IsValid() {
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continue
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}
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c.push(fmt.Sprintf("map[%s]", key))
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c.saveDiff("<does not have key>", b.MapIndex(key))
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c.pop()
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if len(c.diff) >= MaxDiff {
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return
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}
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}
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case reflect.Array:
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n := a.Len()
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for i := 0; i < n; i++ {
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c.push(fmt.Sprintf("array[%d]", i))
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c.equals(a.Index(i), b.Index(i), level+1)
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c.pop()
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if len(c.diff) >= MaxDiff {
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break
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}
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}
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case reflect.Slice:
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if a.IsNil() || b.IsNil() {
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if a.IsNil() && !b.IsNil() {
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c.saveDiff("<nil slice>", b)
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} else if !a.IsNil() && b.IsNil() {
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c.saveDiff(a, "<nil slice>")
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}
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return
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}
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if a.Pointer() == b.Pointer() {
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return
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}
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aLen := a.Len()
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bLen := b.Len()
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n := aLen
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if bLen > aLen {
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n = bLen
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}
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for i := 0; i < n; i++ {
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c.push(fmt.Sprintf("slice[%d]", i))
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if i < aLen && i < bLen {
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c.equals(a.Index(i), b.Index(i), level+1)
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} else if i < aLen {
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c.saveDiff(a.Index(i), "<no value>")
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} else {
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c.saveDiff("<no value>", b.Index(i))
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}
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c.pop()
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if len(c.diff) >= MaxDiff {
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break
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}
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}
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/////////////////////////////////////////////////////////////////////
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// Primitive kinds
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/////////////////////////////////////////////////////////////////////
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case reflect.Float32, reflect.Float64:
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// Avoid 0.04147685731961082 != 0.041476857319611
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// 6 decimal places is close enough
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aval := fmt.Sprintf(c.floatFormat, a.Float())
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bval := fmt.Sprintf(c.floatFormat, b.Float())
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if aval != bval {
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c.saveDiff(a.Float(), b.Float())
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}
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case reflect.Bool:
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if a.Bool() != b.Bool() {
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c.saveDiff(a.Bool(), b.Bool())
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}
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
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if a.Int() != b.Int() {
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c.saveDiff(a.Int(), b.Int())
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}
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case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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if a.Uint() != b.Uint() {
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c.saveDiff(a.Uint(), b.Uint())
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}
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case reflect.String:
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if a.String() != b.String() {
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c.saveDiff(a.String(), b.String())
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}
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default:
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logError(ErrNotHandled)
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}
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}
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func (c *cmp) push(name string) {
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c.buff = append(c.buff, name)
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}
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func (c *cmp) pop() {
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if len(c.buff) > 0 {
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c.buff = c.buff[0 : len(c.buff)-1]
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}
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}
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func (c *cmp) saveDiff(aval, bval interface{}) {
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if len(c.buff) > 0 {
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varName := strings.Join(c.buff, ".")
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c.diff = append(c.diff, fmt.Sprintf("%s: %v != %v", varName, aval, bval))
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} else {
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c.diff = append(c.diff, fmt.Sprintf("%v != %v", aval, bval))
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}
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}
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func logError(err error) {
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if LogErrors {
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log.Println(err)
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}
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}
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