diff options
Diffstat (limited to 'vendor/github.com/google/go-cmp/cmp/path.go')
| -rw-r--r-- | vendor/github.com/google/go-cmp/cmp/path.go | 378 |
1 files changed, 378 insertions, 0 deletions
diff --git a/vendor/github.com/google/go-cmp/cmp/path.go b/vendor/github.com/google/go-cmp/cmp/path.go new file mode 100644 index 000000000..c71003463 --- /dev/null +++ b/vendor/github.com/google/go-cmp/cmp/path.go @@ -0,0 +1,378 @@ +// 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 file. + +package cmp + +import ( + "fmt" + "reflect" + "strings" + "unicode" + "unicode/utf8" + + "github.com/google/go-cmp/cmp/internal/value" +) + +// Path is a list of PathSteps describing the sequence of operations to get +// from some root type to the current position in the value tree. +// The first Path element is always an operation-less PathStep that exists +// simply to identify the initial type. +// +// When traversing structs with embedded structs, the embedded struct will +// always be accessed as a field before traversing the fields of the +// embedded struct themselves. That is, an exported field from the +// embedded struct will never be accessed directly from the parent struct. +type Path []PathStep + +// PathStep is a union-type for specific operations to traverse +// a value's tree structure. Users of this package never need to implement +// these types as values of this type will be returned by this package. +// +// Implementations of this interface are +// StructField, SliceIndex, MapIndex, Indirect, TypeAssertion, and Transform. +type PathStep interface { + String() string + + // Type is the resulting type after performing the path step. + Type() reflect.Type + + // Values is the resulting values after performing the path step. + // The type of each valid value is guaranteed to be identical to Type. + // + // In some cases, one or both may be invalid or have restrictions: + // • For StructField, both are not interface-able if the current field + // is unexported and the struct type is not explicitly permitted by + // an Exporter to traverse unexported fields. + // • For SliceIndex, one may be invalid if an element is missing from + // either the x or y slice. + // • For MapIndex, one may be invalid if an entry is missing from + // either the x or y map. + // + // The provided values must not be mutated. + Values() (vx, vy reflect.Value) +} + +var ( + _ PathStep = StructField{} + _ PathStep = SliceIndex{} + _ PathStep = MapIndex{} + _ PathStep = Indirect{} + _ PathStep = TypeAssertion{} + _ PathStep = Transform{} +) + +func (pa *Path) push(s PathStep) { + *pa = append(*pa, s) +} + +func (pa *Path) pop() { + *pa = (*pa)[:len(*pa)-1] +} + +// Last returns the last PathStep in the Path. +// If the path is empty, this returns a non-nil PathStep that reports a nil Type. +func (pa Path) Last() PathStep { + return pa.Index(-1) +} + +// Index returns the ith step in the Path and supports negative indexing. +// A negative index starts counting from the tail of the Path such that -1 +// refers to the last step, -2 refers to the second-to-last step, and so on. +// If index is invalid, this returns a non-nil PathStep that reports a nil Type. +func (pa Path) Index(i int) PathStep { + if i < 0 { + i = len(pa) + i + } + if i < 0 || i >= len(pa) { + return pathStep{} + } + return pa[i] +} + +// String returns the simplified path to a node. +// The simplified path only contains struct field accesses. +// +// For example: +// MyMap.MySlices.MyField +func (pa Path) String() string { + var ss []string + for _, s := range pa { + if _, ok := s.(StructField); ok { + ss = append(ss, s.String()) + } + } + return strings.TrimPrefix(strings.Join(ss, ""), ".") +} + +// GoString returns the path to a specific node using Go syntax. +// +// For example: +// (*root.MyMap["key"].(*mypkg.MyStruct).MySlices)[2][3].MyField +func (pa Path) GoString() string { + var ssPre, ssPost []string + var numIndirect int + for i, s := range pa { + var nextStep PathStep + if i+1 < len(pa) { + nextStep = pa[i+1] + } + switch s := s.(type) { + case Indirect: + numIndirect++ + pPre, pPost := "(", ")" + switch nextStep.(type) { + case Indirect: + continue // Next step is indirection, so let them batch up + case StructField: + numIndirect-- // Automatic indirection on struct fields + case nil: + pPre, pPost = "", "" // Last step; no need for parenthesis + } + if numIndirect > 0 { + ssPre = append(ssPre, pPre+strings.Repeat("*", numIndirect)) + ssPost = append(ssPost, pPost) + } + numIndirect = 0 + continue + case Transform: + ssPre = append(ssPre, s.trans.name+"(") + ssPost = append(ssPost, ")") + continue + } + ssPost = append(ssPost, s.String()) + } + for i, j := 0, len(ssPre)-1; i < j; i, j = i+1, j-1 { + ssPre[i], ssPre[j] = ssPre[j], ssPre[i] + } + return strings.Join(ssPre, "") + strings.Join(ssPost, "") +} + +type pathStep struct { + typ reflect.Type + vx, vy reflect.Value +} + +func (ps pathStep) Type() reflect.Type { return ps.typ } +func (ps pathStep) Values() (vx, vy reflect.Value) { return ps.vx, ps.vy } +func (ps pathStep) String() string { + if ps.typ == nil { + return "<nil>" + } + s := ps.typ.String() + if s == "" || strings.ContainsAny(s, "{}\n") { + return "root" // Type too simple or complex to print + } + return fmt.Sprintf("{%s}", s) +} + +// StructField represents a struct field access on a field called Name. +type StructField struct{ *structField } +type structField struct { + pathStep + name string + idx int + + // These fields are used for forcibly accessing an unexported field. + // pvx, pvy, and field are only valid if unexported is true. + unexported bool + mayForce bool // Forcibly allow visibility + paddr bool // Was parent addressable? + pvx, pvy reflect.Value // Parent values (always addressable) + field reflect.StructField // Field information +} + +func (sf StructField) Type() reflect.Type { return sf.typ } +func (sf StructField) Values() (vx, vy reflect.Value) { + if !sf.unexported { + return sf.vx, sf.vy // CanInterface reports true + } + + // Forcibly obtain read-write access to an unexported struct field. + if sf.mayForce { + vx = retrieveUnexportedField(sf.pvx, sf.field, sf.paddr) + vy = retrieveUnexportedField(sf.pvy, sf.field, sf.paddr) + return vx, vy // CanInterface reports true + } + return sf.vx, sf.vy // CanInterface reports false +} +func (sf StructField) String() string { return fmt.Sprintf(".%s", sf.name) } + +// Name is the field name. +func (sf StructField) Name() string { return sf.name } + +// Index is the index of the field in the parent struct type. +// See reflect.Type.Field. +func (sf StructField) Index() int { return sf.idx } + +// SliceIndex is an index operation on a slice or array at some index Key. +type SliceIndex struct{ *sliceIndex } +type sliceIndex struct { + pathStep + xkey, ykey int + isSlice bool // False for reflect.Array +} + +func (si SliceIndex) Type() reflect.Type { return si.typ } +func (si SliceIndex) Values() (vx, vy reflect.Value) { return si.vx, si.vy } +func (si SliceIndex) String() string { + switch { + case si.xkey == si.ykey: + return fmt.Sprintf("[%d]", si.xkey) + case si.ykey == -1: + // [5->?] means "I don't know where X[5] went" + return fmt.Sprintf("[%d->?]", si.xkey) + case si.xkey == -1: + // [?->3] means "I don't know where Y[3] came from" + return fmt.Sprintf("[?->%d]", si.ykey) + default: + // [5->3] means "X[5] moved to Y[3]" + return fmt.Sprintf("[%d->%d]", si.xkey, si.ykey) + } +} + +// Key is the index key; it may return -1 if in a split state +func (si SliceIndex) Key() int { + if si.xkey != si.ykey { + return -1 + } + return si.xkey +} + +// SplitKeys are the indexes for indexing into slices in the +// x and y values, respectively. These indexes may differ due to the +// insertion or removal of an element in one of the slices, causing +// all of the indexes to be shifted. If an index is -1, then that +// indicates that the element does not exist in the associated slice. +// +// Key is guaranteed to return -1 if and only if the indexes returned +// by SplitKeys are not the same. SplitKeys will never return -1 for +// both indexes. +func (si SliceIndex) SplitKeys() (ix, iy int) { return si.xkey, si.ykey } + +// MapIndex is an index operation on a map at some index Key. +type MapIndex struct{ *mapIndex } +type mapIndex struct { + pathStep + key reflect.Value +} + +func (mi MapIndex) Type() reflect.Type { return mi.typ } +func (mi MapIndex) Values() (vx, vy reflect.Value) { return mi.vx, mi.vy } +func (mi MapIndex) String() string { return fmt.Sprintf("[%#v]", mi.key) } + +// Key is the value of the map key. +func (mi MapIndex) Key() reflect.Value { return mi.key } + +// Indirect represents pointer indirection on the parent type. +type Indirect struct{ *indirect } +type indirect struct { + pathStep +} + +func (in Indirect) Type() reflect.Type { return in.typ } +func (in Indirect) Values() (vx, vy reflect.Value) { return in.vx, in.vy } +func (in Indirect) String() string { return "*" } + +// TypeAssertion represents a type assertion on an interface. +type TypeAssertion struct{ *typeAssertion } +type typeAssertion struct { + pathStep +} + +func (ta TypeAssertion) Type() reflect.Type { return ta.typ } +func (ta TypeAssertion) Values() (vx, vy reflect.Value) { return ta.vx, ta.vy } +func (ta TypeAssertion) String() string { return fmt.Sprintf(".(%v)", ta.typ) } + +// Transform is a transformation from the parent type to the current type. +type Transform struct{ *transform } +type transform struct { + pathStep + trans *transformer +} + +func (tf Transform) Type() reflect.Type { return tf.typ } +func (tf Transform) Values() (vx, vy reflect.Value) { return tf.vx, tf.vy } +func (tf Transform) String() string { return fmt.Sprintf("%s()", tf.trans.name) } + +// Name is the name of the Transformer. +func (tf Transform) Name() string { return tf.trans.name } + +// Func is the function pointer to the transformer function. +func (tf Transform) Func() reflect.Value { return tf.trans.fnc } + +// Option returns the originally constructed Transformer option. +// The == operator can be used to detect the exact option used. +func (tf Transform) Option() Option { return tf.trans } + +// pointerPath represents a dual-stack of pointers encountered when +// recursively traversing the x and y values. This data structure supports +// detection of cycles and determining whether the cycles are equal. +// In Go, cycles can occur via pointers, slices, and maps. +// +// The pointerPath uses a map to represent a stack; where descension into a +// pointer pushes the address onto the stack, and ascension from a pointer +// pops the address from the stack. Thus, when traversing into a pointer from +// reflect.Ptr, reflect.Slice element, or reflect.Map, we can detect cycles +// by checking whether the pointer has already been visited. The cycle detection +// uses a separate stack for the x and y values. +// +// If a cycle is detected we need to determine whether the two pointers +// should be considered equal. The definition of equality chosen by Equal +// requires two graphs to have the same structure. To determine this, both the +// x and y values must have a cycle where the previous pointers were also +// encountered together as a pair. +// +// Semantically, this is equivalent to augmenting Indirect, SliceIndex, and +// MapIndex with pointer information for the x and y values. +// Suppose px and py are two pointers to compare, we then search the +// Path for whether px was ever encountered in the Path history of x, and +// similarly so with py. If either side has a cycle, the comparison is only +// equal if both px and py have a cycle resulting from the same PathStep. +// +// Using a map as a stack is more performant as we can perform cycle detection +// in O(1) instead of O(N) where N is len(Path). +type pointerPath struct { + // mx is keyed by x pointers, where the value is the associated y pointer. + mx map[value.Pointer]value.Pointer + // my is keyed by y pointers, where the value is the associated x pointer. + my map[value.Pointer]value.Pointer +} + +func (p *pointerPath) Init() { + p.mx = make(map[value.Pointer]value.Pointer) + p.my = make(map[value.Pointer]value.Pointer) +} + +// Push indicates intent to descend into pointers vx and vy where +// visited reports whether either has been seen before. If visited before, +// equal reports whether both pointers were encountered together. +// Pop must be called if and only if the pointers were never visited. +// +// The pointers vx and vy must be a reflect.Ptr, reflect.Slice, or reflect.Map +// and be non-nil. +func (p pointerPath) Push(vx, vy reflect.Value) (equal, visited bool) { + px := value.PointerOf(vx) + py := value.PointerOf(vy) + _, ok1 := p.mx[px] + _, ok2 := p.my[py] + if ok1 || ok2 { + equal = p.mx[px] == py && p.my[py] == px // Pointers paired together + return equal, true + } + p.mx[px] = py + p.my[py] = px + return false, false +} + +// Pop ascends from pointers vx and vy. +func (p pointerPath) Pop(vx, vy reflect.Value) { + delete(p.mx, value.PointerOf(vx)) + delete(p.my, value.PointerOf(vy)) +} + +// isExported reports whether the identifier is exported. +func isExported(id string) bool { + r, _ := utf8.DecodeRuneInString(id) + return unicode.IsUpper(r) +} |