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// Copyright 2017, 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"
"runtime"
"strings"
"github.com/google/go-cmp/cmp/internal/function"
)
// Option configures for specific behavior of Equal and Diff. In particular,
// the fundamental options (Ignore, Transformer, Comparer, and Default),
// configure how equality is determined.
//
// The fundamental options may be composed with filters (FilterPath, FilterValues,
// and FilterPriority) to control the scope over which they are applied.
//
// The cmp/cmpopts package provides helper functions for creating options that
// may be used with Equal and Diff.
type Option interface {
// filter applies all filters and returns the option that remains.
// Each option may only read s.curPath and call s.callTTBFunc.
//
// An Options is returned only if multiple comparers or transformers
// can apply simultaneously and will only contain values of those types
// or sub-Options containing values of those types.
filter(s *state, vx, vy reflect.Value, t reflect.Type) applicableOption
}
// applicableOption represents the following types:
// Fundamental: noop | ignore | invalid | *comparer | *transformer
// Grouping: Options
type applicableOption interface {
Option
// apply executes the option and reports whether the option was applied.
// Each option may mutate s.
apply(s *state, vx, vy reflect.Value) bool
}
// coreOption represents the following types:
// Fundamental: noop | ignore | invalid | *comparer | *transformer
// Filters: *pathFilter | *valuesFilter | *priorityFilter
type coreOption interface {
Option
isCore()
}
type core struct{}
func (core) isCore() {}
// Options is a list of Option values that also satisfies the Option interface.
// Helper comparison packages may return an Options value when packing multiple
// Option values into a single Option. When this package processes Options
// or nested Options, it will be implicitly expanded into a flat set.
type Options []Option
func (opts Options) filter(s *state, vx, vy reflect.Value, t reflect.Type) (out applicableOption) {
for _, opt := range opts {
switch opt := opt.filter(s, vx, vy, t); opt.(type) {
case ignore:
return ignore{} // Highest precedence; can short-circuit filtering
case invalid:
out = invalid{} // Second highest precedence
case noop, *comparer, *transformer, Options:
switch out.(type) {
case nil:
out = opt
case invalid:
// Keep invalid
case noop, *comparer, *transformer, Options:
if opt == (noop{}) && out == (noop{}) {
break // Coelesce redundant Default together
}
out = Options{out, opt} // Conflicting Comparer, Tranformer, or Default
}
}
}
return out
}
func (opts Options) apply(s *state, _, _ reflect.Value) bool {
const warning = "ambiguous set of applicable options"
const help = "consider using filters to ensure at most one Comparer, Transformer, or Default may apply"
var ss []string
for _, opt := range flattenOptions(nil, opts) {
ss = append(ss, fmt.Sprint(opt))
}
set := strings.Join(ss, "\n\t")
panic(fmt.Sprintf("%s at %#v:\n\t%s\n%s", warning, s.curPath, set, help))
}
func (opts Options) String() string {
var ss []string
for _, opt := range opts {
ss = append(ss, fmt.Sprint(opt))
}
return fmt.Sprintf("Options{%s}", strings.Join(ss, ", "))
}
// FilterPath returns a new Option where opt is only applicable if filter f
// returns true for the current Path in the value tree.
//
// The Option passed in may be a filtered option (via the Filter functions),
// fundamental option (like Ignore, Transformer, Comparer, or Default), or
// Options group containing elements of the former.
func FilterPath(f func(Path) bool, opt Option) Option {
if f == nil {
panic("invalid path filter function")
}
if opt := normalizeOption(opt); opt != nil {
return &pathFilter{fnc: f, opt: opt}
}
return nil
}
type pathFilter struct {
core
fnc func(Path) bool
opt Option
}
func (f pathFilter) filter(s *state, vx, vy reflect.Value, t reflect.Type) applicableOption {
if f.fnc(s.curPath) {
return f.opt.filter(s, vx, vy, t)
}
return nil
}
func (f pathFilter) String() string {
fn := getFuncName(reflect.ValueOf(f.fnc).Pointer())
return fmt.Sprintf("FilterPath(%s, %v)", fn, f.opt)
}
// FilterValues returns a new Option where opt is only applicable if filter f,
// which is a function of the form "func(T, T) bool", returns true for the
// current pair of values being compared. If the type of the values is not
// assignable to T, then this filter implicitly returns false.
//
// The filter function must be
// symmetric (i.e., agnostic to the order of the inputs) and
// deterministic (i.e., produces the same result when given the same inputs).
// If T is an interface, it is possible that f is called with two values with
// different concrete types that both implement T.
//
// The Option passed in may be a filtered option (via the Filter functions),
// fundamental option (like Ignore, Transformer, Comparer, or Default), or
// Options group containing elements of the former.
func FilterValues(f interface{}, opt Option) Option {
v := reflect.ValueOf(f)
if !function.IsType(v.Type(), function.ValueFilter) || v.IsNil() {
panic(fmt.Sprintf("invalid values filter function: %T", f))
}
if opt := normalizeOption(opt); opt != nil {
vf := &valuesFilter{fnc: v, opt: opt}
if ti := v.Type().In(0); ti.Kind() != reflect.Interface || ti.NumMethod() > 0 {
vf.typ = ti
}
return vf
}
return nil
}
type valuesFilter struct {
core
typ reflect.Type // T
fnc reflect.Value // func(T, T) bool
opt Option
}
func (f valuesFilter) filter(s *state, vx, vy reflect.Value, t reflect.Type) applicableOption {
if !vx.IsValid() || !vy.IsValid() {
return invalid{}
}
if (f.typ == nil || t.AssignableTo(f.typ)) && s.callTTBFunc(f.fnc, vx, vy) {
return f.opt.filter(s, vx, vy, t)
}
return nil
}
func (f valuesFilter) String() string {
fn := getFuncName(f.fnc.Pointer())
return fmt.Sprintf("FilterValues(%s, %v)", fn, f.opt)
}
// FilterPriority returns a new Option where an option, opts[i],
// is only applicable if no fundamental options remain after applying all filters
// in all prior options, opts[:i].
//
// In order to prevent further options from being applicable, the Default option
// can be used to ensure that some fundamental option remains.
//
// The Option passed in may be a filtered option (via the Filter functions),
// fundamental option (like Ignore, Transformer, Comparer, or Default), or
// Options group containing elements of the former.
func FilterPriority(opts ...Option) Option {
var newOpts []Option
for _, opt := range opts {
if opt := normalizeOption(opt); opt != nil {
newOpts = append(newOpts, opt)
}
}
if len(newOpts) > 0 {
return &priorityFilter{opts: newOpts}
}
return nil
}
type priorityFilter struct {
core
opts []Option
}
func (f priorityFilter) filter(s *state, vx, vy reflect.Value, t reflect.Type) applicableOption {
for _, opt := range f.opts {
if opt := opt.filter(s, vx, vy, t); opt != nil {
return opt
}
}
return nil
}
func (f priorityFilter) String() string {
var ss []string
for _, opt := range f.opts {
ss = append(ss, fmt.Sprint(opt))
}
return fmt.Sprintf("FilterPriority(%s)", strings.Join(ss, ", "))
}
// Default is an Option that configures Equal to stop processing options and
// to proceed to the next evaluation rule (i.e., checking for the Equal method).
// This value is intended to be combined with FilterPriority to act as a
// sentinel type that prevents other options from being applicable.
// It is an error to pass an unfiltered Default option to Equal.
func Default() Option { return noop{} }
type noop struct{ core }
func (noop) isFiltered() bool { return false }
func (noop) filter(_ *state, _, _ reflect.Value, _ reflect.Type) applicableOption { return noop{} }
func (noop) apply(_ *state, _, _ reflect.Value) bool { return false }
func (noop) String() string { return "Default()" }
// Ignore is an Option that causes all comparisons to be ignored.
// This value is intended to be combined with FilterPath or FilterValues.
// It is an error to pass an unfiltered Ignore option to Equal.
func Ignore() Option { return ignore{} }
type ignore struct{ core }
func (ignore) isFiltered() bool { return false }
func (ignore) filter(_ *state, _, _ reflect.Value, _ reflect.Type) applicableOption { return ignore{} }
func (ignore) apply(_ *state, _, _ reflect.Value) bool { return true }
func (ignore) String() string { return "Ignore()" }
// invalid is a sentinel Option type to indicate that some options could not
// be evaluated due to unexported fields.
type invalid struct{ core }
func (invalid) filter(_ *state, _, _ reflect.Value, _ reflect.Type) applicableOption { return invalid{} }
func (invalid) apply(s *state, _, _ reflect.Value) bool {
const help = "consider using AllowUnexported or cmpopts.IgnoreUnexported"
panic(fmt.Sprintf("cannot handle unexported field: %#v\n%s", s.curPath, help))
}
// Transformer returns an Option that applies a transformation function that
// converts values of a certain type into that of another.
//
// The transformer f must be a function "func(T) R" that converts values of
// type T to those of type R and is implicitly filtered to input values
// assignable to T. The transformer must not mutate T in any way.
// If T and R are the same type, an additional filter must be applied to
// act as the base case to prevent an infinite recursion applying the same
// transform to itself (see the SortedSlice example).
//
// The name is a user provided label that is used as the Transform.Name in the
// transformation PathStep. If empty, an arbitrary name is used.
func Transformer(name string, f interface{}) Option {
v := reflect.ValueOf(f)
if !function.IsType(v.Type(), function.Transformer) || v.IsNil() {
panic(fmt.Sprintf("invalid transformer function: %T", f))
}
if name == "" {
name = "λ" // Lambda-symbol as place-holder for anonymous transformer
}
if !isValid(name) {
panic(fmt.Sprintf("invalid name: %q", name))
}
tr := &transformer{name: name, fnc: reflect.ValueOf(f)}
if ti := v.Type().In(0); ti.Kind() != reflect.Interface || ti.NumMethod() > 0 {
tr.typ = ti
}
return tr
}
type transformer struct {
core
name string
typ reflect.Type // T
fnc reflect.Value // func(T) R
}
func (tr *transformer) isFiltered() bool { return tr.typ != nil }
func (tr *transformer) filter(_ *state, _, _ reflect.Value, t reflect.Type) applicableOption {
if tr.typ == nil || t.AssignableTo(tr.typ) {
return tr
}
return nil
}
func (tr *transformer) apply(s *state, vx, vy reflect.Value) bool {
// Update path before calling the Transformer so that dynamic checks
// will use the updated path.
s.curPath.push(&transform{pathStep{tr.fnc.Type().Out(0)}, tr})
defer s.curPath.pop()
vx = s.callTRFunc(tr.fnc, vx)
vy = s.callTRFunc(tr.fnc, vy)
s.compareAny(vx, vy)
return true
}
func (tr transformer) String() string {
return fmt.Sprintf("Transformer(%s, %s)", tr.name, getFuncName(tr.fnc.Pointer()))
}
// Comparer returns an Option that determines whether two values are equal
// to each other.
//
// The comparer f must be a function "func(T, T) bool" and is implicitly
// filtered to input values assignable to T. If T is an interface, it is
// possible that f is called with two values of different concrete types that
// both implement T.
//
// The equality function must be:
// • Symmetric: equal(x, y) == equal(y, x)
// • Deterministic: equal(x, y) == equal(x, y)
// • Pure: equal(x, y) does not modify x or y
func Comparer(f interface{}) Option {
v := reflect.ValueOf(f)
if !function.IsType(v.Type(), function.Equal) || v.IsNil() {
panic(fmt.Sprintf("invalid comparer function: %T", f))
}
cm := &comparer{fnc: v}
if ti := v.Type().In(0); ti.Kind() != reflect.Interface || ti.NumMethod() > 0 {
cm.typ = ti
}
return cm
}
type comparer struct {
core
typ reflect.Type // T
fnc reflect.Value // func(T, T) bool
}
func (cm *comparer) isFiltered() bool { return cm.typ != nil }
func (cm *comparer) filter(_ *state, _, _ reflect.Value, t reflect.Type) applicableOption {
if cm.typ == nil || t.AssignableTo(cm.typ) {
return cm
}
return nil
}
func (cm *comparer) apply(s *state, vx, vy reflect.Value) bool {
eq := s.callTTBFunc(cm.fnc, vx, vy)
s.report(eq, vx, vy)
return true
}
func (cm comparer) String() string {
return fmt.Sprintf("Comparer(%s)", getFuncName(cm.fnc.Pointer()))
}
// AllowUnexported returns an Option that forcibly allows operations on
// unexported fields in certain structs, which are specified by passing in a
// value of each struct type.
//
// Users of this option must understand that comparing on unexported fields
// from external packages is not safe since changes in the internal
// implementation of some external package may cause the result of Equal
// to unexpectedly change. However, it may be valid to use this option on types
// defined in an internal package where the semantic meaning of an unexported
// field is in the control of the user.
//
// For some cases, a custom Comparer should be used instead that defines
// equality as a function of the public API of a type rather than the underlying
// unexported implementation.
//
// For example, the reflect.Type documentation defines equality to be determined
// by the == operator on the interface (essentially performing a shallow pointer
// comparison) and most attempts to compare *regexp.Regexp types are interested
// in only checking that the regular expression strings are equal.
// Both of these are accomplished using Comparers:
//
// Comparer(func(x, y reflect.Type) bool { return x == y })
// Comparer(func(x, y *regexp.Regexp) bool { return x.String() == y.String() })
//
// In other cases, the cmpopts.IgnoreUnexported option can be used to ignore
// all unexported fields on specified struct types.
func AllowUnexported(types ...interface{}) Option {
if !supportAllowUnexported {
panic("AllowUnexported is not supported on App Engine Classic or GopherJS")
}
m := make(map[reflect.Type]bool)
for _, typ := range types {
t := reflect.TypeOf(typ)
if t.Kind() != reflect.Struct {
panic(fmt.Sprintf("invalid struct type: %T", typ))
}
m[t] = true
}
return visibleStructs(m)
}
type visibleStructs map[reflect.Type]bool
func (visibleStructs) filter(_ *state, _, _ reflect.Value, _ reflect.Type) applicableOption {
panic("not implemented")
}
// reporter is an Option that configures how differences are reported.
type reporter interface {
// TODO: Not exported yet.
//
// Perhaps add PushStep and PopStep and change Report to only accept
// a PathStep instead of the full-path? Adding a PushStep and PopStep makes
// it clear that we are traversing the value tree in a depth-first-search
// manner, which has an effect on how values are printed.
Option
// Report is called for every comparison made and will be provided with
// the two values being compared, the equality result, and the
// current path in the value tree. It is possible for x or y to be an
// invalid reflect.Value if one of the values is non-existent;
// which is possible with maps and slices.
Report(x, y reflect.Value, eq bool, p Path)
}
// normalizeOption normalizes the input options such that all Options groups
// are flattened and groups with a single element are reduced to that element.
// Only coreOptions and Options containing coreOptions are allowed.
func normalizeOption(src Option) Option {
switch opts := flattenOptions(nil, Options{src}); len(opts) {
case 0:
return nil
case 1:
return opts[0]
default:
return opts
}
}
// flattenOptions copies all options in src to dst as a flat list.
// Only coreOptions and Options containing coreOptions are allowed.
func flattenOptions(dst, src Options) Options {
for _, opt := range src {
switch opt := opt.(type) {
case nil:
continue
case Options:
dst = flattenOptions(dst, opt)
case coreOption:
dst = append(dst, opt)
default:
panic(fmt.Sprintf("invalid option type: %T", opt))
}
}
return dst
}
// getFuncName returns a short function name from the pointer.
// The string parsing logic works up until Go1.9.
func getFuncName(p uintptr) string {
fnc := runtime.FuncForPC(p)
if fnc == nil {
return "<unknown>"
}
name := fnc.Name() // E.g., "long/path/name/mypkg.(mytype).(long/path/name/mypkg.myfunc)-fm"
if strings.HasSuffix(name, ")-fm") || strings.HasSuffix(name, ")·fm") {
// Strip the package name from method name.
name = strings.TrimSuffix(name, ")-fm")
name = strings.TrimSuffix(name, ")·fm")
if i := strings.LastIndexByte(name, '('); i >= 0 {
methodName := name[i+1:] // E.g., "long/path/name/mypkg.myfunc"
if j := strings.LastIndexByte(methodName, '.'); j >= 0 {
methodName = methodName[j+1:] // E.g., "myfunc"
}
name = name[:i] + methodName // E.g., "long/path/name/mypkg.(mytype)." + "myfunc"
}
}
if i := strings.LastIndexByte(name, '/'); i >= 0 {
// Strip the package name.
name = name[i+1:] // E.g., "mypkg.(mytype).myfunc"
}
return name
}