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[github/fretlink/terraform-provider-statuscake.git] / vendor / github.com / google / go-cmp / cmp / options.go

// 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"
        "regexp"
        "strings"

        "github.com/google/go-cmp/cmp/internal/function"
)

// Option configures for specific behavior of Equal and Diff. In particular,
// the fundamental Option functions (Ignore, Transformer, and Comparer),
// configure how equality is determined.
//
// The fundamental options may be composed with filters (FilterPath and
// FilterValues) 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, t reflect.Type, vx, vy reflect.Value) applicableOption
}

// applicableOption represents the following types:
//      Fundamental: ignore | validator | *comparer | *transformer
//      Grouping:    Options
type applicableOption interface {
        Option

        // apply executes the option, which may mutate s or panic.
        apply(s *state, vx, vy reflect.Value)
}

// coreOption represents the following types:
//      Fundamental: ignore | validator | *comparer | *transformer
//      Filters:     *pathFilter | *valuesFilter
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 an Options,
// it will be implicitly expanded into a flat list.
//
// Applying a filter on an Options is equivalent to applying that same filter
// on all individual options held within.
type Options []Option

func (opts Options) filter(s *state, t reflect.Type, vx, vy reflect.Value) (out applicableOption) {
        for _, opt := range opts {
                switch opt := opt.filter(s, t, vx, vy); opt.(type) {
                case ignore:
                        return ignore{} // Only ignore can short-circuit evaluation
                case validator:
                        out = validator{} // Takes precedence over comparer or transformer
                case *comparer, *transformer, Options:
                        switch out.(type) {
                        case nil:
                                out = opt
                        case validator:
                                // Keep validator
                        case *comparer, *transformer, Options:
                                out = Options{out, opt} // Conflicting comparers or transformers
                        }
                }
        }
        return out
}

func (opts Options) apply(s *state, _, _ reflect.Value) {
        const warning = "ambiguous set of applicable options"
        const help = "consider using filters to ensure at most one Comparer or Transformer 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 evaluated if filter f
// returns true for the current Path in the value tree.
//
// This filter is called even if a slice element or map entry is missing and
// provides an opportunity to ignore such cases. The filter function must be
// symmetric such that the filter result is identical regardless of whether the
// missing value is from x or y.
//
// The option passed in may be an Ignore, Transformer, Comparer, Options, or
// a previously filtered Option.
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, t reflect.Type, vx, vy reflect.Value) applicableOption {
        if f.fnc(s.curPath) {
                return f.opt.filter(s, t, vx, vy)
        }
        return nil
}

func (f pathFilter) String() string {
        return fmt.Sprintf("FilterPath(%s, %v)", function.NameOf(reflect.ValueOf(f.fnc)), f.opt)
}

// FilterValues returns a new Option where opt is only evaluated 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 either value is invalid or
// 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 an Ignore, Transformer, Comparer, Options, or
// a previously filtered Option.
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, t reflect.Type, vx, vy reflect.Value) applicableOption {
        if !vx.IsValid() || !vx.CanInterface() || !vy.IsValid() || !vy.CanInterface() {
                return nil
        }
        if (f.typ == nil || t.AssignableTo(f.typ)) && s.callTTBFunc(f.fnc, vx, vy) {
                return f.opt.filter(s, t, vx, vy)
        }
        return nil
}

func (f valuesFilter) String() string {
        return fmt.Sprintf("FilterValues(%s, %v)", function.NameOf(f.fnc), f.opt)
}

// 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.Type, _, _ reflect.Value) applicableOption { return ignore{} }
func (ignore) apply(s *state, _, _ reflect.Value)                                   { s.report(true, reportByIgnore) }
func (ignore) String() string                                                       { return "Ignore()" }

// validator is a sentinel Option type to indicate that some options could not
// be evaluated due to unexported fields, missing slice elements, or
// missing map entries. Both values are validator only for unexported fields.
type validator struct{ core }

func (validator) filter(_ *state, _ reflect.Type, vx, vy reflect.Value) applicableOption {
        if !vx.IsValid() || !vy.IsValid() {
                return validator{}
        }
        if !vx.CanInterface() || !vy.CanInterface() {
                return validator{}
        }
        return nil
}
func (validator) apply(s *state, vx, vy reflect.Value) {
        // Implies missing slice element or map entry.
        if !vx.IsValid() || !vy.IsValid() {
                s.report(vx.IsValid() == vy.IsValid(), 0)
                return
        }

        // Unable to Interface implies unexported field without visibility access.
        if !vx.CanInterface() || !vy.CanInterface() {
                const help = "consider using a custom Comparer; if you control the implementation of type, you can also consider AllowUnexported or cmpopts.IgnoreUnexported"
                panic(fmt.Sprintf("cannot handle unexported field: %#v\n%s", s.curPath, help))
        }

        panic("not reachable")
}

// identRx represents a valid identifier according to the Go specification.
const identRx = `[_\p{L}][_\p{L}\p{N}]*`

var identsRx = regexp.MustCompile(`^` + identRx + `(\.` + identRx + `)*$`)

// 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.
//
// To help prevent some cases of infinite recursive cycles applying the
// same transform to the output of itself (e.g., in the case where the
// input and output types are the same), an implicit filter is added such that
// a transformer is applicable only if that exact transformer is not already
// in the tail of the Path since the last non-Transform step.
// For situations where the implicit filter is still insufficient,
// consider using cmpopts.AcyclicTransformer, which adds a filter
// to prevent the transformer from being recursively applied upon itself.
//
// The name is a user provided label that is used as the Transform.Name in the
// transformation PathStep (and eventually shown in the Diff output).
// The name must be a valid identifier or qualified identifier in Go syntax.
// 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 = function.NameOf(v)
                if !identsRx.MatchString(name) {
                        name = "λ" // Lambda-symbol as placeholder name
                }
        } else if !identsRx.MatchString(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(s *state, t reflect.Type, _, _ reflect.Value) applicableOption {
        for i := len(s.curPath) - 1; i >= 0; i-- {
                if t, ok := s.curPath[i].(Transform); !ok {
                        break // Hit most recent non-Transform step
                } else if tr == t.trans {
                        return nil // Cannot directly use same Transform
                }
        }
        if tr.typ == nil || t.AssignableTo(tr.typ) {
                return tr
        }
        return nil
}

func (tr *transformer) apply(s *state, vx, vy reflect.Value) {
        step := Transform{&transform{pathStep{typ: tr.fnc.Type().Out(0)}, tr}}
        vvx := s.callTRFunc(tr.fnc, vx, step)
        vvy := s.callTRFunc(tr.fnc, vy, step)
        step.vx, step.vy = vvx, vvy
        s.compareAny(step)
}

func (tr transformer) String() string {
        return fmt.Sprintf("Transformer(%s, %s)", tr.name, function.NameOf(tr.fnc))
}

// 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, t reflect.Type, _, _ reflect.Value) applicableOption {
        if cm.typ == nil || t.AssignableTo(cm.typ) {
                return cm
        }
        return nil
}

func (cm *comparer) apply(s *state, vx, vy reflect.Value) {
        eq := s.callTTBFunc(cm.fnc, vx, vy)
        s.report(eq, reportByFunc)
}

func (cm comparer) String() string {
        return fmt.Sprintf("Comparer(%s)", function.NameOf(cm.fnc))
}

// 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.
//
// In many 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 purego builds, Google App Engine Standard, 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.Type, _, _ reflect.Value) applicableOption {
        panic("not implemented")
}

// Result represents the comparison result for a single node and
// is provided by cmp when calling Result (see Reporter).
type Result struct {
        _     [0]func() // Make Result incomparable
        flags resultFlags
}

// Equal reports whether the node was determined to be equal or not.
// As a special case, ignored nodes are considered equal.
func (r Result) Equal() bool {
        return r.flags&(reportEqual|reportByIgnore) != 0
}

// ByIgnore reports whether the node is equal because it was ignored.
// This never reports true if Equal reports false.
func (r Result) ByIgnore() bool {
        return r.flags&reportByIgnore != 0
}

// ByMethod reports whether the Equal method determined equality.
func (r Result) ByMethod() bool {
        return r.flags&reportByMethod != 0
}

// ByFunc reports whether a Comparer function determined equality.
func (r Result) ByFunc() bool {
        return r.flags&reportByFunc != 0
}

type resultFlags uint

const (
        _ resultFlags = (1 << iota) / 2

        reportEqual
        reportUnequal
        reportByIgnore
        reportByMethod
        reportByFunc
)

// Reporter is an Option that can be passed to Equal. When Equal traverses
// the value trees, it calls PushStep as it descends into each node in the
// tree and PopStep as it ascend out of the node. The leaves of the tree are
// either compared (determined to be equal or not equal) or ignored and reported
// as such by calling the Report method.
func Reporter(r interface {
        // PushStep is called when a tree-traversal operation is performed.
        // The PathStep itself is only valid until the step is popped.
        // The PathStep.Values are valid for the duration of the entire traversal
        // and must not be mutated.
        //
        // Equal always calls PushStep at the start to provide an operation-less
        // PathStep used to report the root values.
        //
        // Within a slice, the exact set of inserted, removed, or modified elements
        // is unspecified and may change in future implementations.
        // The entries of a map are iterated through in an unspecified order.
        PushStep(PathStep)

        // Report is called exactly once on leaf nodes to report whether the
        // comparison identified the node as equal, unequal, or ignored.
        // A leaf node is one that is immediately preceded by and followed by
        // a pair of PushStep and PopStep calls.
        Report(Result)

        // PopStep ascends back up the value tree.
        // There is always a matching pop call for every push call.
        PopStep()
}) Option {
        return reporter{r}
}

type reporter struct{ reporterIface }
type reporterIface interface {
        PushStep(PathStep)
        Report(Result)
        PopStep()
}

func (reporter) filter(_ *state, _ reflect.Type, _, _ reflect.Value) applicableOption {
        panic("not implemented")
}

// 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
}